field user guide

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Field User Guide

<Virtual Environment> 5.9

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Contents

1. Introduction.......................................................................................................52. Menus ................................................................................................................6

2.1. File Menu.............................................................................................................................. 62.1.1. New Project ................................................................................................................. 62.1.2. Open Project................................................................................................................ 82.1.3. Bridge In ...................................................................................................................... 82.1.4. Import V.10, V.11 Project ............................................................................................ 82.1.5. Save Project ................................................................................................................ 82.1.6. Save Project As ........................................................................................................... 92.1.7. Print Output ................................................................................................................. 92.1.8. Print Drawing ............................................................................................................... 92.1.9. Recent File List ............................................................................................................ 92.1.10. Exit............................................................................................................................... 9

2.2. Edit Menu ........................................................................................................................... 102.2.1. Add Circuit ................................................................................................................. 102.2.2. Add Board.................................................................................................................. 122.2.3. Delete ........................................................................................................................ 132.2.4. Edit............................................................................................................................. 142.2.5. Find Node Reference ................................................................................................ 252.2.6. Design Data............................................................................................................... 262.2.7. Predefined Data......................................................................................................... 302.2.8. Loads Data ................................................................................................................ 32

2.3. View Menu.......................................................................................................................... 422.3.1. Zoom In...................................................................................................................... 422.3.2. Zoom Out................................................................................................................... 442.3.3. Zoom All..................................................................................................................... 442.3.4. Refresh ...................................................................................................................... 442.3.5. Axis Lock ................................................................................................................... 442.3.6. Export DXF ................................................................................................................ 452.3.7. Print Drawing ............................................................................................................. 452.3.8. Grid ............................................................................................................................ 452.3.9. Font Scale.................................................................................................................. 462.3.10. Dynamic Scroll........................................................................................................... 462.3.11. Quick Draw ................................................................................................................ 462.3.12. Fence Overlap ........................................................................................................... 46

2.4. Database Menu .................................................................................................................. 472.4.1. Devices ...................................................................................................................... 472.4.2. Cables........................................................................................................................ 472.4.3. Database Path........................................................................................................... 49

2.5. Calculations Menu.............................................................................................................. 512.5.1. Network Calculations................................................................................................. 512.5.2. Single-Circuit Calculation .......................................................................................... 522.5.3. CostPlan Output ........................................................................................................ 52

2.6. Review Menu...................................................................................................................... 532.6.1. Input Data .................................................................................................................. 532.6.2. Messages .................................................................................................................. 542.6.3. Equipment Load Balance .......................................................................................... 552.6.4. General Load Summary ............................................................................................ 552.6.5. Fixed Schedules ........................................................................................................ 562.6.6. Customised Schedules.............................................................................................. 572.6.7. Key to Schedules....................................................................................................... 602.6.8. Equipment Analysis ................................................................................................... 612.6.9. Load Schedule........................................................................................................... 612.6.10. Distribution Equipment Schedule .............................................................................. 62

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2.6.11. Device Schedule........................................................................................................ 622.6.12. Cable Schedule ......................................................................................................... 632.6.13. Abbreviations and Codes .......................................................................................... 632.6.14. Output File ................................................................................................................. 64

2.7. Help Menu .......................................................................................................................... 642.7.1. Contents .................................................................................................................... 642.7.2. Help on Help.............................................................................................................. 642.7.3. About ......................................................................................................................... 65

3. Tool Buttons....................................................................................................663.1. Main Toolbar ...................................................................................................................... 663.2. Status Bar........................................................................................................................... 66

4. Selection of Boards and Circuits ..................................................................675. Program Size Limits .......................................................................................736. Voltage Drops .................................................................................................747. Customised Schedules ..................................................................................758. Calculation Methods.......................................................................................77

8.1. Load Summation ................................................................................................................ 778.1.1. General ...................................................................................................................... 778.1.2. Connected Load ........................................................................................................ 778.1.3. Design Load on Final Circuits.................................................................................... 778.1.4. Design Load on Distribution Circuits ......................................................................... 798.1.5. Design Current .......................................................................................................... 798.1.6. Neutral Current .......................................................................................................... 79

8.2. Device Selection/Checking ................................................................................................ 818.2.1. Basic Factors ............................................................................................................. 818.2.2. Design Current .......................................................................................................... 818.2.3. Starting Current ......................................................................................................... 818.2.4. Inrush Current............................................................................................................ 828.2.5. Discrimination ............................................................................................................ 828.2.6. Standard Circuits ....................................................................................................... 838.2.7. Ratings Set by User................................................................................................... 838.2.8. Fused Connection Units ............................................................................................ 838.2.9. Socket Circuits........................................................................................................... 83

8.3. Cable Sizing/Checking ....................................................................................................... 838.3.1. Basic Factors ............................................................................................................. 838.3.2. Current-carrying Capacity.......................................................................................... 858.3.3. Circuit Voltage Drop .................................................................................................. 868.3.4. Short Circuit ............................................................................................................... 868.3.5. Earth Fault ................................................................................................................. 888.3.6. Indirect Contact ......................................................................................................... 908.3.7. Maximum Grouping ................................................................................................... 918.3.8. Maximum Length ....................................................................................................... 918.3.9. k-factors..................................................................................................................... 91

9. Standard Data Used in the Program .............................................................939.1. Protective Device Data....................................................................................................... 93

9.1.1. Standard Data ........................................................................................................... 939.1.2. Discrimination Between Fuses .................................................................................. 939.1.3. Device Selection on Motor Circuits ........................................................................... 949.1.4. BS1362 Fuses ........................................................................................................... 949.1.5. s-factors..................................................................................................................... 94

9.2. Conductor Data .................................................................................................................. 959.2.1. Cable Types .............................................................................................................. 959.2.2. Impedances ............................................................................................................... 979.2.3. Motor Data ................................................................................................................. 979.2.4. Customised Schedule Data ....................................................................................... 97

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1. Introduction

Field is a program for the design and analysis of electrical installations inaccordance with BS 7671, Requirements for Electrical Installations (formerly the16th. Edition of the IEE Wiring Regulations), with Amendment No. 1, 1994. Allreferences to BS 7671 refer to that edition. Field assists at all stages of adesign, from provisional, with only basic network and load details, to final, withdetails of all final circuits and including spare capacity and diversity. However, itis merely a design tool; all major decisions are left to the engineer/user, such asthe types of protective devices or cables to use and the setting of voltage-droplimits for the various sections of the installation.

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2. Menus

The menu bar has the following options: File, Edit, View, Database,Calculations, Review, and Help. Each of these is described in detail in thissection.

2.1. File Menu

2.1.1. New Project

The New Project command allows a new Field project to be created. On selectingthis option, a standard Windows New Project dialogue box will appear. Use thisdialogue box to browse through the structure of your computer system to where youwish to locate your Field project. Enter the required *.fpr file name and click on theSave button.

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The new Field document will be opened and all pull-down menus on the menu barwill become active. Since you are opening a new project, the Design Data dialoguebox will be displayed to remind you to edit the design data (see Design Data). If youhad a project open already before you selected this command, the existing projectwill be closed. You can save a project using the Save command.

Note if an existing project named seed.fpr exists in the Field folder below whereField.exe was installed, this is used to “seed” the new project. You may use thisfacility to help you make a quicker start on every new project, by defining your typicaldesign data and predefined data in a project, and copying it to the correct area,renaming it to seed.fpr. A sample seed project named seed1.fpr is provided for you.To use this, simply rename it to seed.fpr. (It is deliberately named differently toprevent accidentally overwriting your seed.fpr if you install a new version of Field.)

The caption now shows the name of the Field project file name on the title barfollowed by the name of the program, e.g. “c:\demo\fldtrnex.fpr – IES Field”.

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2.1.2. Open Project

The Open Project command allows you to read an existing Field project that has theextension .fpr. A standard Windows Open File dialogue box will appear. Use thisdialogue box to browse through the structure of your computer system, select therequired .fpr file and click on the Open button.

The existing Field document will be opened and all pull-down menus on the menubar will become active. Since you are opening an existing project, the Design datadialogue box will not be displayed. If you had a project open already before youselected this command, the existing project will be closed. You can save a projectusing the Save command.

Again, the caption now shows the name of the Field project file name on the title barfollowed by the name of the program, e.g. “c:\demo\fldtrnex.fpr – IES Field”.

2.1.3. Bridge In

The Bridge In facility allows you to locate and open files created by bridging out fromInterFacet ELECTRICAL or from BSE. These are currently in the older *.f16 format,with all the actual data stored in separate files in a Field folder below the *.f16 file.Select a *.f16 file using the standard Windows Open File dialogue box, and pressOpen. The old-style *.f16 file and all its associated data files will be converted to anew-style Field project file.

2.1.4. Import V.10, V.11 Project

The Import V.10, V.11 Project facility allows you to locate and open files in the older*.f16 format, with all the actual data stored in separate files in a Field folder belowthe *.f16 file. This is the format used in versions 10 and 11 of Field. Select a *.f16 fileusing the standard Windows Open File dialogue box, and press Open. The old-style*.f16 file and all its associated data files will be converted to a new-style Field projectfile.

Note this is exactly the same as Bridge In because the format created by bridgingout is the same.

2.1.5. Save Project

You can use this command to save the current *.fpr project file at any time under theexisting name, without closing the project.

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2.1.6. Save Project As

You can use this command to save the current *.fpr project file at any time under anew name and location on your computer system.

On selecting this option, a standard Windows Save As dialogue box will appear. Usethis dialogue box to browse through the structure of your computer system to whereyou wish to locate your Field project. Enter the required *.fpr file name and click onthe Save button.

2.1.7. Print Output

This option allows you to print the output file in its current state, whether or not youhave saved it. The printer dialogue box will default to Landscape for this option.

Note the output file is temporary and will be deleted when you close Field. To keep apermanent copy of the output file it must be saved. See Review > Output File forhow to do this.

2.1.8. Print Drawing

This option allows you to print the part of the drawing that is visible in the Graphicswindow. If you wish to print the complete network you would need to ensure that it isall visible first by selecting the View > Zoom All menu option. The printer dialoguebox will default to Landscape for this option.

2.1.9. Recent File List

These 4 options list the 4 most-recently used projects as a convenience. Selectingone of these is the same as using the Open Project option and finding the file.

2.1.10. Exit

This command exits from Field. If you have made any changes to the *.fpr file, youwill be given the option to save the amended file.

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2.2. Edit Menu

2.2.1. Add Circuit

Use this command to add a new circuit to the drawing. After pressing the button theprompt will change as shown in the status bar below.

Move the cursor to the point from which you want the circuit to start (the NEARnode). This may be anywhere on the blank space (to place a disconnected circuit),or on one of the outgoing ways (FAR node) of a board that is already placed (inmore usual circumstances). In the former case a new node number will be used, andin the latter case the node number will be picked up from the board. The cursor willautomatically detect the proximity of the slot and snap to it. Click the mouse and the

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start point will be fixed. In this example a circuit is being placed on the yellow slot ofway 6 on the board MSB.

Note at any stage you may press the right mouse button to cancel placement.

The prompt then changes as shown below to ask you to drag the other end of thecircuit.

Move the cursor to the point at which you want the circuit to end (the FAR node).Again, this may be a point either anywhere in the blank space or on the feeder area(NEAR node) of a board that is already placed (anywhere along the bottom of theboard). In the former case a new node number will be used, and in the latter casethe node number will be picked up from the board. The cursor will automaticallydetect the proximity of the feeder area and snap to it. Click the mouse and the endpoint will be fixed. In this example the circuit is to be unconnected at the far end.

The circuit is now placed. Note that it now also appears in the text list above thegraphics area.

If you have made a previous circuit the default for new circuits, the circuit will pick upall of the data from that previous circuit, except of course for the way number, phase,and node numbers (see Edit for details of how to do this).

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2.2.2. Add Board

Use this command to add a new board to the drawing. After pressing the button theprompt will change as shown in the status bar below.

Move the cursor to the point from which you want the board to be fed (the NEARnode). This may be anywhere on the blank space (to place a disconnected board),or on the far end (FAR node) of a circuit that is already placed (in more usualcircumstances). In the former case a new node number will be used, and in the lattercase the node number will be picked up from the circuit. The cursor will automaticallydetect the proximity of the end of the circuit and snap to it. Click the mouse and thefeed point will be fixed. In this example a board is being placed on the end of thenew circuit.

Note at any stage you may press the right mouse button to cancel placement.

The prompt then changes as shown below to ask you to drag the other end of theboard to select its orientation.

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This allows you to drag the board into a horizontal or vertical orientation. If thedirection from the start point to the cursor is more vertical than horizontal, the boardis oriented vertically; otherwise it is oriented horizontally. Click the mouse and theorientation will be fixed. In this example the board is to be represented vertically toshow a busbar.

The board is now placed. It now also appears in the text list above the graphics area.

Note the FAR node of the board is always set equal to the NEAR node plus 1.

If you have made a previous board the default for new boards the board will pick upall of the data from that previous board, except of course for the node numbers (seeEdit for details of how to do this).

2.2.3. Delete

Use this command to delete all the circuits or boards that have been selected. Youwill be prompted to confirm the action.

Note to select boards or circuits for deleting see Selection of Boards and Circuits.

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2.2.4. Edit

Use this command to edit the circuit or board that has been selected. Only one itemmust be selected for editing. To select boards or circuits for editing see Selection ofBoards and Circuits. The dialogue box that appears now depends on whether it is acircuit or a board.

2.2.4.1. Circuit

When you are editing a circuit the Edit Circuit dialogue box appears. This has a caption toindicate which circuit is being edited and eight tabs. One useful feature to note is that thetab that was active when this dialogue box was last closed is reactivated the next time it isopened.

The General Tab

This allows you to enter general data for the circuit.

Way Number Enter the number of the way from which this circuit is fed.Isolated (Not used at present) Toggle this on if you wish this circuit and all boards and circuits

downstream of it to be isolated from the source of power.Description Enter a description of this circuit. It is for information only and will appear on certain

output schedules.Phase Select a phase for this circuit.Route Length Enter the route length for this circuit. This is not needed on final circuits because Field

will attempt to calculate a maximum length if it is set to zero.Effective Length This will default to the route length. Enter a different value if you know that, from the

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for Voltage Drop distribution of loads, the voltage drop would be over calculated by assuming that all ofthe loads are at the far end of the circuit. E.g. if the loads are evenly distributed alongthe circuit, the effective length is half the route length.

Length to BusbarTake-off

If the feeding board is a busbar with significant impedance, the calculation of voltagedrops and fault currents will be more accurate if you enter the length along the feedingboard from the point where the board itself is fed to the point where this circuit is takenoff. The busbar impedances are entered elsewhere, in the Edit Board dialogue box forthe feeding board.

Essential CircuitSub-contactor?

Toggle this on if you wish. It is for information only and will appear on certain outputschedules.

Comments Enter comments if you wish. It is for information only and will appear on certain outputschedules.

Diversity (%) Enter diversity to apply to upstream load if circuit load is not always drawn.Make Default Press this button to make this circuit the default for any circuits you subsequently add to

the network. This is designed for speeding up data entry by allowing you to place atypical circuit, edit it to requirements, and then make it the default for any future circuits.Note only a pointer to this circuit is stored; therefore changes you make to this circuitafter making it the default will also be made to the default.

The Circuit Tab

This allows you to enter further details about the layout of this circuit. It is deliberately thesame as the Circuit tab in the Predefined Data dialogue box (see Predefined Data),because the items defined there may be used here if desired.

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Maintain Link toPredefined Data

If you select one of the predefined circuit layouts you may choose whether tomaintain a link to it. If you do, and you subsequently re-edit the predefined circuitlayout, the changes will be reflected in this circuit and any other circuit that hasmaintained a link to it. If you do not, the link is broken and the data is embeddedinstead

Predefined CircuitDetails

If you have predefined any circuit layouts these will be available for selection here tospeed up the process

Name This read-only box shows the name of the predefined layout selectedDescription This read-only box shows the description of the predefined layout selectedProtective Device Select a device to use on this circuit (use the special option if none is required)Protective DeviceRating (A)

Select a rating for this device if you wish to fix it, or 0 if you wish Field to calculate theminimum rating required.

Voltage Drop LimitWithin the Circuit (%or V)

Set a limit for the voltage drop from one end of this circuit to the other. This will be in% of the supply voltage, or in volts, depending on what you chose in the Design Datadialogue box (see Design Data). Use this figure on various circuits to get Field tocalculate sizes that satisfy the OVERALL voltage drop limits. The upper limit is 4%.

Overall Voltage DropLimit (% or V)

Set a limit for the overall voltage drop from the nominal voltage at the supply to theend of this circuit. This must include the voltage drop at the supply which you enteredin the Design Data dialogue box (see Design Data). BS7671 says that 4% or less,not including the supply voltage drop, will be deemed to satisfy the voltage droprequirements, so the upper limit is 4% plus the supply voltage drop. See also abovefor units

AmbientTemperature (C)

Enter the ambient air temperature around this circuit under normal runningconditions.

Configuration Select Ring for a ring circuit, Radial for a radial circuit, or Spare if the circuit is to bekept spare for future needs (therefore not wired up yet). Note that distribution circuitsmust be radial

Standard Circuit Select a standard circuit layout from 433-02-04 of the 15th. Edition if you wish to use

one, or None otherwise. Cannot be used on Distribution circuits.Paste Settings (Adjustable devices only.) Use this button to paste in the device settings for the

adjustable device that were edited and copied using the Edit Settings button below.Note that the device and rating must match that for which the settings were editedand copied.

Reset Settings (Adjustable devices only.) Use this button to clear the device settings for theadjustable device. After this the device will revert to its default settings when used onthis circuit.

Edit Settings (Adjustable devices only.) Use this button to edit the device settings for thisadjustable device. The rating must be selected (i.e. non-zero) for this option to work.The Field Device Database Editor will open and the edit settings box will be shownfor the selected device and rating. After adjusting the settings you may press thecopy button and close the dialogues down. The paste button can then be used topaste back the settings to this circuit. (See the separate document for the FieldDevice Database Editor)

Adjustable DeviceSettings

(Adjustable devices only.) This read-only box shows the current settings for theadjustable device, or blank for the default settings.

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The Cable Tab

This allows you to enter further details about the cable used in this circuit. It is deliberatelythe same as the Cable tab in the Predefined Data dialogue box (see Predefined Data),because the items defined there may be used here if desired.

Maintain link topredefined data

If you select one of the predefined cables you may choose whether to maintain a link toit. If you do, and you subsequently re-edit the predefined cable, the changes will bereflected in this circuit and any other circuit that has maintained a link to it. If you do not,the link is broken and the data is embedded instead.

Predefined cabledetails

If you have predefined any cables these will be available for selection here to speed upthe process.

Name This read-only box shows the name of the predefined cable selected.Description This read-only box shows the description of the predefined cable selected.Cable type Select a cable type.Phase Select one of the following codes for the phase of the cable, to enable Field to check the

installation method:

TPN : three-phase and neutral (4-wire)TP : three-phase (3-wire)SPN : single-phase and neutral (2-wire)

For single-phase we are not interested in which phase is to be used, so in this case SPNis used instead of R, Y, or B.

Note that only pre-defined circuits of matching phase can be used.Installationmethod

Select an installation method from the list. You will only be allowed to select one that isappropriate to the cable type and phase code entered in the previous items.

Installation methods used in Field are based on those in Appendix 4 of BS 7671 (except* and U). They usually comprise two parts:

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The first part is the installation method from BS 7671, or * when the installation methodis irrelevant, or U for underground (not used at present).

The second part (where applicable) is one of these qualifying letters:H: horizontal, V: vertical, F: flat, T: trefoil, S: small duct, L: large duct.

Minimum andmaximum no. ofparallel cables

Limit, if required, the number of parallel cables Field is free to select on a circuit.Otherwise use 0 (no limit).

Minimum andmaximum cablesize

Limit, if required, the size of cables Field is free to select on a circuit. Otherwise use 0(no limit). You will only be allowed to select a size that is appropriate to the cable type,phase code and installation method entered in the previous items.

Grouping Enter if known, the number of grouped circuits or multicore cables as defined inAppendix 4 of BS7671. Otherwise enter 0 and Field will calculate the maximum groupingallowed.

Spacing Select the spacing between grouped cables if known.Thermalinsulationderating factor

See Regulation 523-04-01. If the cable is not embedded in thermal insulation, enter 1.Otherwise the derating factor which must be applied to this cable depends on the lengthof the cable embedded in thermal insulation. Select a value from Table 52A of theRegulations if the cable size is up to 10 mm², embedded less than 0.5 m in insulation ofthermal conductivity greater than 0.0625 W/Km. For longer lengths the Regulationsadvise a value of 0.5.For other conditions a guidance note is given (not yet available: 18/10/91).If you enter less than 1, installation method 1F will be used automatically, as required bythe Regulations (though it is open to interpretation whether this should be the case whenTable 52A or the guidance note is used). The installation method you have entered willbe ignored.

Use Equation 2 ofBS7671Appendix 4

Appendix 4 of BS 7671 gives equations for the sizing of cables with regard to current-carrying capacity for normal and overload conditions. Field usually uses a generalisedequation that is equivalent to equations (1), (2), (5) or (6), but is referred to as equation(2) for convenience.

If the circuit is grouped with other circuits and they are not liable to simultaneousoverload, Appendix 4 of BS 7671 allows the use of alternate equations. Field uses twogeneralised equations, one equivalent to equations (3) or (7), but referred to as equation(3) for convenience, and one equivalent to equations (4) or (8), but referred to asequation (4) for convenience.

See Cable Sizing/Checking - Current-carrying Capacity for details of these generalisedequations.

Turn on or off to indicate whether equation (2) or equations (3) and (4) together shouldbe used to calculate the required tabulated single-circuit current-carrying capacity.

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The Protective Conductor Tab

This allows you to enter further details about the circuit protective conductor (CPC) used inthis circuit. It is deliberately the same as the Protective conductor tab in the PredefinedData dialogue box (see Predefined Data), because the items defined there may be usedhere if desired.

Maintain link topredefined data

If you select one of the predefined CPC’s you may choose whether to maintain a linkto it. If you do, and you subsequently re-edit the predefined CPC, the changes will bereflected in this circuit and any other circuit that has maintained a link to it. If you donot, the link is broken and the data is embedded instead.

Predefined CPCdetails

If you have predefined any CPC’s these will be available for selection here to speedup the process.

Name This read-only box shows the name of the predefined CPC selected.Description This read-only box shows the description of the predefined CPC selected.Use armour/sheathof live cable

Select this if you wish to use the armour or sheath of the cable carrying the liveconductors. This option should not be used if there is no armour/sheath.

Use core of livecable

Select this if you wish to use a spare core of the cable carrying the live conductors.This option should not be used if there is no spare core.

Use separate cable Select this if you wish to use a separate cable. This should normally be a single-corecable. The separate cable type, length and size should be entered if this option ischosen. The size may be left blank for Field to select. The length may be left blankon final circuits only.

Use conduit Select this if you wish to use a metallic conduit. The length and diameter should beentered if this option is chosen. The length may be left blank on final circuits only.

Use trunking Select this if you wish to use trunking. The length, cross-sectional area, material anddimensions should be entered if this option is chosen. The length may be left blankon final circuits only.

Series or parallel Select this to determine whether the elements chosen (if more than one) should be inseries or parallel. Note that armour/sheath and core can only be in parallel with other

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elements because they run the whole length of the cable. Note also that only 13combinations of elements and series/parallel are available. Whenever an element isselected the unavailable combinations are disabled.

The Loading Tab

This allows you to select one or more predefined loads to be used on this circuit. Datashould be entered on this tab for final circuits only. Select a load from the left-hand list andpress Add >> to add it to the list of loads used on this circuit. Select a load in the right-handlist and use the Quantity text box or spin-button to alter the number of loads of this type touse on the circuit, or press Remove to remove it.

Instead of, or in addition to, using a predefined load, you may define a provisional load forthe circuit, in VA or amps. Select the units required and press the provisional load button(this is labelled with the current value). This opens the following form:

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Here you may enter your load into any two of the three boxes. The other box isautomatically calculated to be the correct value. The leading button may be toggled on if thephase is leading. The above example shows a load defined in amps, where the userentered 23 A for the magnitude and 0.95 for the power factor. After dismissing this box thelabel on the button changes as shown.

The Messages Tab

This displays any messages related to this circuit, and any messages for the project as awhole (not related to any circuit). Messages are (in order of decreasing severity) errors,warnings and comments, sent to alert you to problems reading the data (Import or Bridge Inonly), or in the calculations. Select one of the option buttons to choose which levels ofseverity to show. Errors may never be suppressed. The Print button prints a list of themessages, and the Add to output button adds the messages to the output file. Thesebuttons use the same severity selection.

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The Diagnostics Tab

This allows you to review the diagnostic log that was produced for each circuit duringcalculations if the Create diagnostic log of calculations for each circuit toggle button wasturned on in the Design Data dialogue box beforehand. These diagnostic logs were addedto improve confidence in the Field calculations by allowing you to examine the values andequations used at each step. The problem has been that Field makes more accurate useof, for example, power factors (both in summing loads and in calculating voltage drops) andtemperature corrections, than many manual calculations, giving rise to different results andoccasional support calls. Now they are more easily obtained, because previously they couldbe requested for one circuit only and had to be stored and re-read from a file. Thediagnostic log also gives an insight into the way a stage of a calculation, and all theprevious stages, are repeated with larger and larger cables until the criterion for that stageis satisfied, before going on to the next stage of the calculation.

Note work is still in progress to give fuller diagnostic logs, especially of the load summationand fault calculations.

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The Results Tab

This gives you a basic summary of the most useful results of the calculation. These mayalso be printed. The two other buttons show plots of voltage drops and device characteristiccurves for this circuit and for all circuits upstream to the supply point.

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2.2.4.2. Board

When you are editing a board the Edit Board dialogue box appears.

Name Enter a board name. This should be unique.Number of ways Enter the number of ways allowed to be taken from this board. A three-phase way

counts as one way even if three single-phase circuits are taken from it.Isolated (Not used at present) Toggle this on if you wish this board and all circuits and boards

downstream of it to be isolated from the source of power.Description Enter a description of this board. It is for information only and will appear on certain

output schedules.Busbarimpedance

If the type (see below) is a busbar with appreciable conductor impedances, then youneed to enter here the resistances and reactances per metre of the live, neutral andearth conductors of the busbar. These are used in calculating extra contributions tovoltage drop and to fault impedances for the circuits fed from various take-off pointsalong this busbar.

Board type Select the type of board that best fits the board you wish to enter.Phase Select the phase of this board.Display boardvertically

Toggle this on if you wish to display the board vertically. This is done for youautomatically if you select a busbar type, but in any case you may override the choice.

Include sparecapacity anddiversity

Toggle this on to specify either spare capacity, or diversity, or both, for this board. Youwill then need to enter data in the boxes below.

Balanced (Only visible on three-phase boards) Toggle this on to enter one set of values for allthree phase, or off to enter different values on each phase.

Spare capacity Use the button to bring up a standard dialogue box to enter the spare capacity on eachselected phase.

Third harmonic(%)

Enter a third harmonic contribution expected in the spare capacity on each selectedphase.

Diversity (%) Enter diversity for each selected phase. Note this applies to the total load on the board,

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not just to the spare capacity.Includeprovisionalloading data

Toggle this on if you wish to add a provisional load to the board. This may be used inplace of defining any circuits at the initial stages of a design. You will then need to enterdata in the boxes below.

Provisional load Use the button to bring up a standard dialogue box to enter the provisional load.Protective devicetype

If there is a protective device that you expect to be associated with the load beingdefined provisionally here, select it from the list. This allows you to ensure that Field willattempt to size the device feeding this board to discriminate with the device you enterhere.

Protective devicerating

If a protective device was selected above, select its rating from the list.

Make Default Press this button to make this board the default for any boards you subsequently add tothe network. This is designed for speeding up data entry by allowing you to place atypical board, edit it to requirements, and then make it the default for any future boards.(NOTE only a pointer to this board is stored; therefore changes you make to this boardafter making it the default will also be made to the default.

2.2.5. Find Node Reference

Use this command to find all occurrences of a particular node. The Find NodeNumber dialogue box appears as shown. When you enter a node number and pressFind Next, the first circuit or board with that node number will be highlighted, both inthe text list and in the graphics area. Further presses highlight further circuits orboards with that node number until no more are found.

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2.2.6. Design Data

Use this command to edit the design data by bringing up the design data dialoguebox.

Project title Enter a title for this project. This will appear on the top of each page of output.Earthing Select an earthing method. See BS7671 for details.Phase Select a phase.Nominal voltage (V) Enter the nominal supply voltage: phase-phase (line voltage) if the supply is three-

phase, phase-neutral otherwise.Frequency (Hz) Enter supply frequency, used to convert inductance to inductive reactance.Largest voltage dropexpected at thesupply (% or V)

Enter the maximum voltage drop expected at the supply to the network, as apercentage of the nominal supply voltage or in volts, depending on the units selectedbelow.

% of nominal voltage Select this to show all voltage drops and voltage drop limits as a percentage of thenominal supply voltage.

V Select this to show all voltage drops and voltage drop limits in volts.

Enter values in the next section to help Field to calculate the short circuit and earthfault impedance of the supply, which are needed in all the short-circuit and earth-fault calculations:

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Supply fault level (MVA) Select this and enter a value if the fault level of the supply is known.Transformer details Select this and enter the transformer rating (kVA) and impedance (%) if these

values are known. Enter the power rating of the transformer (assumed to be in astar/delta configuration) If the transformer impedance is not known a value maybe entered from this table:

kVA 5 16 125 315 800 1000 1250 2500 5000 6300Z (%) 4.75 4.75 4.75 4.75 4.75 4.75 5.0 6.0 6.0 7.0

Both the above Select this and enter the values if both of the above sets of values are known.Short-circuit current(kA)

Select this and enter the short-circuit current if known. Enter the fault current (forthe LV side if a transformer is used) at the supply to the network.

Short-circuit impedance(% to 100 MVA base)

Select this if none of the above values are known; you will need to enter somevalues here instead. If unsure, enter some very low values for the minima andsome very high values for the maxima. For details about how to calculate these,see Calculated Supply Short-Circuit Impedances below.

Earth-fault impedances(ohms)

See Calculated DEFAULT Supply Earth-Fault Impedance below.

2.2.6.1. Calculated Supply Short-Circuit Impedances

If you select any of the first 4 options, the data entered will be used to calculate themaximum and minimum supply short-circuit resistances and reactances. The resistanceand reactance are assumed equal (i.e. phase angle = 45°) and the minimum and maximumvalues are also assumed equal. If these assumptions are too inaccurate, you may calculatethe values using this section as a guide and enter them directly in the 5th option.

The calculations are as follows (V=Nominal Voltage from above and the 2 represents the45° assumption):

a) If Fault Level F (MVA) was entered:

10,000 for 3-phase supply, or 10,000 for single-phase supply2 F 3 2 F

b) If Transformer Rating TR (kVA) and Impedance TI (%) were entered:

100,000 TI for 3-phase supply, or 100,000 TI for single-phase supply2 TR 3 2 TR

c) If Short Circuit Current SC (kA) was entered:

10,000,000 for 3-phase supply, or 10,000,000 for single-phase supply2 3 V SC 3 2 V SC

d) If a) and b) are both true, the calculated values are added together.

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2.2.6.2. Calculated DEFAULT Supply Earth-Fault Impedance

If you select any of the first 4 options, the data entered will be used to calculate the valuesof supply earth-fault resistance and reactance. The impedance is assumed to be reactiveonly (i.e. phase angle=90°) so the default resistive component is zero.

The default reactive component is calculated as follows (V=Nominal Voltage from above):

a) If Fault Level F (MVA) was entered:

V²1,000,000 3 F

b) If Transformer Rating TR (kVA) and Impedance TI (%) were entered:

V² TI100,000 TR

c) If Short Circuit Current SC (kA) was entered:

V3,000 SC

d) If a) and b) are both true, the calculated values are added together.

Protective device ratingsafety margins

Enter safety margins to be applied to the calculated minimum device rating foreach of the categories. The value must not be less than 1 to satisfy BS 7671Regulation 433-02-01(i).

Minimum ambienttemperature (deg. C)

Enter the minimum ambient temperature. This is used in calculating maximumfault currents in the network.

Minimum conduit size(mm)

Enter a value for the minimum conduit size. This is the minimum diameter forany conduit used within the installation. A typical value is 16 mm. Select adiameter from the values 16, 20, 25 and 32.

Minimum protective devicerating for motor circuits (A)

Enter the minimum device rating for circuits feeding cage-type inductionmotors. This is used in selecting motor-circuit protective-devices.

Motor-fuse links arerequired on all motorcircuits

If toggled on, Field will select motor-circuit fuse-links on all motor circuits. Thechoice for any particular circuit may be overridden if required.

Create diagnostic log ofcalculations for each circuit

If toggled on, any subsequent calculation will produce a full diagnostic log foreach circuit, which can be examined by editing the circuit.

Automatically add inputdata to output

If toggled on, a record of all the input data will automatically be added to theoutput file just before calculations are requested.

Edit starting factors (“S-factors”)

Press this button to edit s-factors – see below.

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s (starting)-factors are used to ensure that the device rating does not trip during the startingperiod (see Protective device data – s-factors).

Enter s-factor values for the various load types and for numbers of occurrences of theseload types from 1 to 6. Note that s-factors should decrease with increasing number ofoccurrences.

For each number of occurrences of each load type, Field obtains the minimum device ratingfor the inrush current by multiplying the total normal running current of all the loads of thistype by the relevant s-factor.

For mixed load types the sum of the individual contributions is used.

The s-factors must then be deduced by working back from data provided by the load ordevice manufacturers, showing either recommended ratings or starting- current envelopesfor various numbers of occurrences of the loads. At best this is a compromise between thedifferent load and device types and manufacturers.

Default values are provided when new projects are started, as below:

Default s-factors Number of occurrences of load typeLoad type 1 2 3 4 5 6+Lamp Type I 4.000 2.500 2.000 1.700 1.500 1.500Lamp Type F 4.000 3.800 2.400 2.200 2.100 2.000Lamp Type SOX 6.700 3.800 2.400 2.200 2.100 2.000Lamp Type SON 6.700 3.800 2.400 2.200 2.100 2.000Lamp Type MBF 6.700 3.800 2.400 2.200 2.100 2.000Lamp Type MBT 6.700 3.800 2.400 2.200 2.100 2.000Lamp Type MBI 6.700 3.800 2.400 2.200 2.100 2.000Heaters 1.100 1.100 1.100 1.100 1.100 1.100Cookers 1.100 1.100 1.100 1.100 1.100 1.100Control Panels 4.000 3.800 2.400 2.200 2.100 2.000

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2.2.7. Predefined Data

Use this command to Edit the predefined data for this project. You may usepredefined data to speed up data entry. Up to 100 sets of predefined data, in threecategories, may be set up and stored with a name and description for each. Thecategories are:

Predefined circuit details Predefined cable details Predefined circuit protective conductor (CPC) details

A predefined data set from each category may then be used on any circuit, in one oftwo ways:

As a copy, so that further changes may be made on the copy if desiredAs a link, so that further changes are not allowed but that any changes to thepredefined data will show up in all the circuits using it

The Predefined Data dialogue box uses exactly the same tabs as those on the EditCircuit dialogue box, to make it easier to learn Field. However, there are some smalldifferences:

Predefined Data dialogue box (defining) Edit Circuit dialogue box (referencing)No Maintain link toggle buttons – not needed whendefining.

Maintain link toggle buttons – needed to decidewhether to reference a copy or a link to thepredefined data.

Name and Description edit boxes are enabled –needed when defining.

Name and Description edit boxes are disabled – notneeded when referencing.

Add, Delete and Edit buttons to enable user todefine.

No Add, Delete and Edit buttons – not needed whenreferencing predefined data.

The tabs are shown below. For details of how to enter data, refer to the Edit Circuitdialogue box.

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2.2.7.1. Predefined Circuit Data Tab

2.2.7.2. Predefined Cable Data Tab

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2.2.7.3. Predefined CPC Data Tab

2.2.8. Loads Data

This command brings up the Loads dialogue box. You may use this to define loads,each of which may be used later on as many circuits as you wish. Loads are optionalbecause you may decide to use provisional loading data only at an early stage of adesign. At a later stage you may wish to enter more specific loading details here anduse them on circuits. Loads are divided into eight categories. The Loads datadialogue has eight tabs, one for each category. These are described in the followingsections. However, some of the items are common to all (or nearly all) of the tabsand are described below.

Name Enter a name for this load, up to 4 characters. This name must be unique to this load,i.e. no other load of any type must have the same name. This combo box may also beused for moving between loads for review or edit. As you do this the Current record=item below and all the other items will also change to reflect the load chosen.

Description Enter a description for this load. This will appear on certain output schedules.Number of storedrecords: <n>

This shows you how many loads of this type have been defined (where <n> isreplaced by the actual number).

Current record= This text box or spin button can be used to move from one load to another to review oredit. As you do this the Name item above and all the other items will also change toreflect the load chosen.

Add Use this button, after making changes to the current load in the dialogue box, to add itas a new load at the end of the list of loads. You will prevented from adding a new loaduntil you give it a new name.

Change Use this button, after making changes to the current load in the dialogue box, to save itback to the same place in the list of loads.

Remove Use this button to remove the current load from the list of loads.

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2.2.8.1. Lighting Loads Tab

Available luminaires Select a previously defined luminaire to be used in this lighting group.Quantity Enter the number of luminaires of this type to use in this lighting group.Split Phase If this luminaire is to be used in a three-phase lighting group, select which phase it

is to be used on. Otherwise set Split Phase to No.Edit Luminaires Displays a dialogue box (see Luminaires dialogue box) that allows you to edit the

luminaires used in the project.Add Adds the currently-selected luminaire, quantity and phase to the list of luminaires

used in this lighting group.Remove Removes the currently-selected luminaire, quantity and phase from the list of

luminaires used in this lighting group.Luminaires used inthis lighting group

Shows the luminaires used in this lighting group, with their quantities and phases.

Note you may use a particular luminaire on more than one phase of a split-phase lightinggroup.

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Luminaires Dialogue Box

Name This name may be the same as a lighting group name if you wish, but it must beunique within the list of luminaires.

Lamp type Select the type of lamp from the list.Loading Press this button to edit the loading data.Number of lamps Enter the number of lamps in this luminaire. This is used when finding the s-factor for

the selection of device rating to accommodate inrush current.Lamp rating (W) Enter the output rating of the lamp. This will appear in luminaire schedules.Third harmonic (%) Enter the third harmonic as a percentage of the total circuit current of the luminaire.

Field will take these into account when calculating the out-of-balance currents inneutral conductors.

Device type Select a device if one is incorporated in the luminaire. Field will take account of thisin discrimination calculations.

Device rating (A) Select the rating of the device.

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2.2.8.2. Motor Loads Tab

Status Select Duty or Standby. Standby motors will be excluded from the load summation,but the device and cable will still be sized.

Phases Select 1 or 3 phases.Poles Select the number of poles. When standard motor data is used, this enables Field

to find the relevant standard data.Starting method Select one of the starting methods. If non-standard is selected, you must enter the

starting current and duration below. If star-delta with non-localised starter isselected, Field will calculate the size of the cable assuming that there are six cablesto the motor, instead of three.

Starting current (A) If the starting method is non-standard, enter the starting current. Field will comparethe point given by the maximum starting current and duration to the characteristicsfor the relevant device type and select the lowest rating whose characteristicpasses above the point.

Starting duration (s) If the starting method is non-standard, enter the starting duration.Output rating (kW) If standard motor data is used, but a non-standard rating is entered, Field will adjust

the motor characteristics by interpolation or extrapolation.Efficiency (%) Enter the motor efficiency. If standard motor data (see Motor Data) is not required,

enter data in 2 items out of this one and the next two (power factor and full-loadcurrent). Press the ? button to calculate it from the other values.

Power factor Enter the power factor. Press the ? button to calculate it from the other values. Thecalculated value is:

Output Rating(Efficiency x No. of Phases x Full-Load Current x Phase Voltage).

Full load current (A) Enter the full-load current of the motor. Press the ? button to calculate it from theother values. The calculated value is:

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Output Rating(Efficiency x No. of Phases x Power Factor x Phase Voltage).

Set these 3 itemsusing standard motordata

This button will use standard motor data to fill in suggested values for the threeitems above, based on the number of phases, the number of poles, and the outputrating.

Overcurrent trip (%) If a value is entered, Field will base the current-carrying capacity of the final circuitcable on I = trip/100 x full-load current of the motor. If no over-current trip isrequired, enter 0.

Fused connectionunit?

Select Yes if the load is single-phase and connected by FCU, No otherwise. Fieldwill indicate on output schedules where equipment is connected by FCU. Forstandard circuits (A1, A2 or A3) Field will assume connection by FCU.

Protective device type If there is a protective device incorporated into the load being defined here, select itfrom the list.

Protective devicerating

If a protective device was selected above, select its rating from the list.

2.2.8.3. Heater Loads Tab

Load (kW) Enter a load in kW. The power factor is assumed to be 1.Phases Select 1 or 3 phases.Fusedconnection unit?

Select Yes if the load is single-phase and connected by FCU, No otherwise. Field willindicate on output schedules where equipment is connected by FCU. For standardcircuits (A1, A2 or A3) Field will assume connection by FCU.

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2.2.8.4. Cooker Loads Tab

Load (kW) Enter a load in kW. The power factor is assumed to be 1.Phases Select 1 or 3 phases.Socket outlet present? Select Yes if the load is a single-phase cooking appliance with a socket outlet

included, No otherwise. This is used in calculating diversity as in Appendix 4 ofthe IEE Regulations (15th. Edition)..

Diversity If the above is toggled off, enter the diversity of the cooking appliance. The designload will be calculated as this percentage of the connected load.

Use default diversityfrom regulations?

Toggle on if you wish Field to use the diversity from table 4A of the IEERegulations (15th. Edition) for Household cooking appliances. The design loadwill be calculated as this percentage of the connected load.

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2.2.8.5. Socket Loads Tab

Socket type Select one of the following socket types:

BS1363 13A (1-phase only, single or twin outlets)BS546 2, 5, 15, 30A (1-phase only, single outlets only)BS196 5, 15, 30A (1-phase only, single outlets only)BS5550 15A (1-phase only, single outlets only)BS4343 16, 32, 63, 125A (1 or 3-phase, single outlets only)US-STYLE 15, 20A (1-phase only, single or twin outlets, 110V)

Rating (A) Enter a rating. This must be one of the allowed ratings for the socket type.Number of singles Enter the number of single socket outlets in this socket group. These are used in

calculating the aggregate rating of the socket group.Number of twins Enter the number of twin socket outlets in this socket group. These are used in

calculating the aggregate rating of the socket group. Note that some socket types areavailable as single outlets only.

Phases Select 1 or 3 phases.Loading Use this button to enter a total loading for the group of sockets. Field will use this to

calculate the connected load for the circuit on which this socket load is used. Thesame value will be added into the connected load and the design load for thedistribution equipment. However, the design load for the circuit itself will be calculatedas in Load summation – design load on final circuits, for the reasons given there.

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2.2.8.6. Control Panel Tab

Set Load (kW) Use this button to set the load kW, kVA and power factor.Phases Select 1 or 3 phases.Diversity Enter the diversity. The design load will be calculated as this percentage of the

connected load.Third harmonic (%) Enter the third harmonic as a percentage of the total circuit current of the load.

Field will take account of third harmonics when calculating out-of-balancecurrents in the neutral conductor.

Starting current (A) Not required for control panels.Starting duration (s) Not required for control panels.Overall voltage drop limit(% or V)

See Regulation 525-01. Enter the overall voltage-drop limit (including thevoltage drop at the supply) to be imposed on the circuit feeding this controlpanel. This will be in % of the supply voltage, or in volts, depending on what youchose in the Design Data dialogue box (see Design Data). The warning limitsare between the supply voltage drop +0.1 percent and +4.0 percent, and theerror limits are between the supply voltage drop plus 0.1 percent and 20percent.

State Select Duty or Standby. Standby loads will be excluded from the loadsummation, but the device and cable will still be sized.

Fused connection unit? Select Yes if the load is single-phase and connected by FCU, No otherwise.Field will indicate on output schedules where equipment is connected by FCU.For standard circuits (A1, A2 or A3) Field will assume connection by FCU.

Protective device type If there is a protective device incorporated into the load being defined here,select it from the list.

Protective device rating If a protective device was selected above, select its rating from the list.

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2.2.8.7. Elevators Tab

See Control Panel tab. The only differences here are that the starting current and durationmay be entered and that the Diversity must be 100%:

Diversity Diversity must be 100% for elevators. The design load will be calculated as thispercentage of the connected load.

Starting current (A) Enter the maximum starting current and duration if you want Field to size theprotective device for the starting current. Field will compare the point given bythe maximum starting current and duration to the characteristics for the relevantdevice type and select the lowest rating whose characteristic passes above thepoint.

Starting duration (s) Enter the starting duration (see above).

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2.2.8.8. Others Tab

See Control Panel tab. The only differences here are that the starting current and durationmay be entered.

Starting current (A) Enter the maximum starting current and duration if you want Field to size theprotective device for the starting current. Field will compare the point given bythe maximum starting current and duration to the characteristics for the relevantdevice type and select the lowest rating whose characteristic passes above thepoint.

Starting duration (s) Enter the starting duration (see above).

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2.3. View Menu

Note the view menu is also available using the right mouse button in thegraphics area.

2.3.1. Zoom In

Use this command to expand a part of the graphics window to fill the whole window.When you select the command the prompt in the status bar changes as below.

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Move the mouse pointer to one corner of the area you wish to expand (the zoomrectangle). Press the button and hold it down while you move the mouse pointer.This will start dragging the other corner of the zoom rectangle as shown below.

When you release the mouse button the zoom rectangle is expanded to fit into theview as shown below. Note that even though the zoom rectangle may be a differentshape from your window, the zoom will be performed in such a way that the entirerectangle will still be visible.

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2.3.2. Zoom Out

Use this command to zoom out so that approximately twice the area is now visible inyour graphics window.

2.3.3. Zoom All

Use this command to zoom to fit the entire network into your graphics window.

2.3.4. Refresh

Use this command to redraw the network in your graphics window in case any of thedragging, etc. has left traces on the screen.

2.3.5. Axis Lock

Use this command to restrict node drags and circuit placement so that your secondmouse click is restricted to have either the same x-coordinate or the same y-coordinate as your first mouse click, i.e. it locks movement to either the x or ycoordinate axis. This is useful in certain circumstances.

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2.3.6. Export DXF

Use this command to export the entire network graphic in DXF format. Thiscommand does not depend on the current view zoom. A Windows standard SaveFile dialogue box will open asking you for the file name. When you press Save youwill be asked whether you wish to export the layer table, and then the file will becreated.

2.3.7. Print Drawing

This is identical to the same option on the File menu (see Print Drawing).

2.3.8. Grid

Use this command to turn on or off a grid in the graphics window. When the grid ison any placement or drag will be restricted to grid points. This may be used to tidyup alignments of circuits, boards, etc. Note that the grid is only visible at high enoughzoom magnification.

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2.3.9. Font Scale

Use this command to adjust the size of the text in the graphics window. The factoryou enter is relative to the standard value (=1).

Note this affects the text size on printouts as well as in the graphics window.

2.3.10. Dynamic Scroll

This affects how scrolling occurs. When it is off, the graphic area is not redrawn untilyou stop dragging the “thumb” on the scroll-bar, making it harder to scroll precisely.When it is on, you can see the graphic area being redrawn dynamically while the“thumb” is being dragged. Because this makes scrolling slightly slower, only outlinesare shown during dynamic scrolling.

2.3.11. Quick Draw

When this is on, only outlines will be drawn, for increased speed.

2.3.12. Fence Overlap

When this is on, any elements intersecting the selection fence are also included inthe selection.

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2.4. Database Menu

2.4.1. Devices

Use this command to edit and review protective devices from the database. Thisruns the device database editor Fielddb.exe, which may also be run standalone, i.e.directly from Windows, if you wish. See the separate document Field DeviceDatabase Editor User Guide for details.

2.4.2. Cables

Use this command to edit and review cables from the database. The Cable databasedialogue box opens, allowing you to select a cable from a list box.

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This has several buttons:

Import - this allows you to import new cables from text files. Not available yet Export - this allows you to export selected cables to text files. Not available yet. Copy - this allows you to copy a cable from another Field database. Not available yet. Add - this allows you to add and edit a new cable. The Field cable database editor will

open. See Edit. Review - this allows you to see the data for the selected cable. The Review dialogue

box opens to show you the relevant data.

Edit - this allows you to edit the selected cable. The Field cable databaseeditor will open.

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Delete - this allows you to delete the selected cable. Close - this closes the Cable database dialogue box.

2.4.3. Database Path

The custom database path is the location of the system database on your system.This is where system-wide data is available for Field to use, comprising devices,cables, and customised output schedule formats.

If the DOS environment variable Field has been set, then the initial custom databasepath is set to that path, for all Field projects. Otherwise the initial custom databasepath is blank, for all Field projects. If the custom database path is blank, then Fielduses the system database from the Field folder below where Field.exe is installed.Otherwise, Field uses the database from this path. Note wherever the systemdatabase is located; any user changes to the database are always stored in the localdatabase, not the system database. The local database is in the Field folder belowthe project.

Use this command to set or change the custom database path for the current projectonly. The Custom Database Path dialogue box opens, with a box showing thecurrent path (if any):

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To clear the current path (if any) select it and press Remove.

Press Browse to browse around your system for a folder where a Field database canbe found. This opens a Windows standard Browse for Folder dialogue box (shownbelow).

Press OK when the path is correctly set or cleared, or Cancel to revert to theprevious setting.

If you press OK the new path will then be saved with the project.

To set or change the custom database path for all projects that do not have theirown path already set; you must use the Field DOS environment variable. Theeasiest way to do this is to put a line set Field =<required path> in the fileautoexec.bat.

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2.5. Calculations Menu

The Calculations menu allows you to select which calculation you wish toperform.

2.5.1. Network Calculations

Selecting this command allows you to run the standard network calculations. First ofall, a question appears:

Answer Yes if you want to start afresh with an empty output file, or No to keep whatis already in the output file, maybe from a previous calculation. If you have selectedautomatically add input data to output on the Design Data dialogue box then asummary of the input data will be added to the output file at this point. Thecalculations will then proceed, unless there are errors preventing this.

The calculations include the following (see Calculation methods for more details):

Load summation (connected load and design load), including neutral-currentand third-harmonic contribution.

Sizing/checking of device ratings for design load, for starting or inrush currentand for discrimination against other devices.

Sizing/checking of cables for design load, for voltage drop and for short-circuit and earth-fault energy withstand and disconnection time.

Sizing/checking of CPC's for similar design constraints.

Incidental results obtained also include maximum groupings, short-circuit and earth-fault currents, impedances, energy let-throughs and disconnection times, and circuitand overall voltage drops.

The number and type of calculations performed by Field will depend on the data youenter and the results you require. In particular the device, cable and CPC sizing willonly be performed if you have not set the sizes on input. If you have, the sizes youhave set will be checked instead.

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When the calculations are complete, you will be given a count of errors, warningsand comments. You may review these messages using the Review Messages option(see Messages).

2.5.2. Single-Circuit Calculation

Selecting this command allows you to perform a single-circuit calculation on theselected circuit only. Not available at present.

2.5.3. CostPlan Output

Selecting this command allows you to produce output to file that can be used asinput to CostPlan. The file will automatically be named the same as the project filebut with a *.cst extension.

CostPlan will then need to be run separately using this file as input.

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2.6. Review Menu

The Review menu includes commands that let you review input data,messages, and various types of results. All review options that come to screenmay also be printed or added to the output file. Most of them appear in aresizable Review dialogue box, the contents of which may be scrolled,selected, copied, added to output or printed.

2.6.1. Input Data

This option brings up a sub-menu of the different types of input data:

The Review Input Data menu consists of:

Design Data Predefined Data Load Data Network Data

Use these options to review the data required. Each set of data is shown in a Reviewdialogue box.

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2.6.2. Messages

This option displays the Messages dialogue box. This contains a Messages tab (seebelow), very similar to the one used in the Edit Circuit dialogue box (see TheMessages Tab). The only differences are:

The top pane lists messages for circuits in general rather than for the oneparticular circuit being edited.

When one or more of these messages are highlighted the appropriate circuitsare also highlighted in the text list and the graphics area on the main window.This can be useful to help you to identify the parts of a network having aparticular type of problem. So, for example, to see all the circuits which haveerrors, select Show errors only, and then highlight all the error messages; or,to see all circuits with voltage drop problems, highlight the appropriatemessages – it may give you a clue as to the cause, because all the circuitsmay be fed from a particular board.

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2.6.3. Equipment Load Balance

This option produces a drawing of all the boards selected, or the 8 most unbalancedboards, showing a little histogram of loads split by phase, so that you can visualisethe balance between phases.

2.6.4. General Load Summary

This option displays a general load summary in a Review dialogue box. This is asummation of all loads on a board-by-board basis.

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2.6.5. Fixed Schedules

This option displays the Fixed Output Schedules dialogue box. At present two fixedschedule formats are available, Basic Schedule and Detailed Schedule. They aresuitable for reviewing most of the fundamental data on a board-by-board basis.

Select all the boards for which you wish to have schedules in the left-hand pane.Use Select All or Clear All to speed up the process. Select the required schedule inthe right-hand pane. Then press Create Schedules to create all the requestedschedules. These appear in a Review dialogue box.

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2.6.6. Customised Schedules

This option displays the Customised Output Schedules dialogue box. There areseveral customised output schedule formats (although some of these are examplesnot meant to be used in real situations) and it is possible for you to create and edityour own in addition.

Select all the boards for which you wish to have schedules in the left-hand pane.Use Select All or Clear All to speed up the process. Select the required schedule inthe right-hand pane. Then press Create Schedules to create all the requestedschedules. These appear in a Review dialogue box.

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Press Edit Schedules if you wish to edit the formats (templates) for customisedoutput schedules. The Field Customised Output Schedules dialogue box will open.

Selecting a schedule and pressing Add will add a new schedule based on theselected schedule, and bring up the edit box for this new schedule. Selecting aschedule and pressing Edit will bring up the edit box for the currently-selectedschedule. In either case the Edit Customised Schedule dialogue box will appear.

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The top tabs represent different types of circuit data (input and results) that areavailable for use in your schedule format. The bottom tabs represent the items ofdata already in use, arranged according to section. Two sections represent the maintable (Part 1) and a continuation table (Part 2), and four sections represent total lineswhich show data from the circuit feeding the board in question. The arrows allow theorder of data in any section to be modified. Follow the instructions on screen formodifying the layout of your customised schedule by selecting items from the toptabs for inclusion in any of the bottom tabs, or by removing or changing the order ofitems in the bottom tabs. At any stage the View button may be used to examine theeffects of the changes you are making. This is the fastest way to learn what thedifferent sections mean, because the View Schedule dialogue box shows them laidout as in the finished schedule.

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2.6.7. Key to Schedules

This option displays the key to symbols used in the schedules in a Review dialoguebox.

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2.6.8. Equipment Analysis

This option displays a breakdown of load demand by load type.

2.6.9. Load Schedule

This option displays a summary of loads of each type, with the quantity used.

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2.6.10. Distribution Equipment Schedule

This option displays a summary of all the distribution equipment, showing the largestdevice and the maximum short circuit current.

2.6.11. Device Schedule

This option displays the schedule of devices and quantities by rating and number ofphases.

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2.6.12. Cable Schedule

This option displays a schedule of cables, quantities and total lengths by size andnumber of cores.

2.6.13. Abbreviations and Codes

This option displays the abbreviations and codes used in Field, in a Review dialoguebox.

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2.6.14. Output File

This option displays the output file. This uses a different type of dialogue box whichallows you to print the output file and/or save it. If it is not saved, it will be lost at theend of a Field session.

2.7. Help Menu

2.7.1. Contents

This option displays the help file for Field. Note pressing F1 at any stage will bring upthis help file, on a suitable page according to where the cursor was when F1 waspressed.

2.7.2. Help on Help

This option displays the standard Windows “Help on Help” help file, telling you moreabout how to use the Windows Help system.

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2.7.3. About

This option displays the “About” dialogue box. The caption of this box is the quickestand most reliable way to find out what version of Field you are running (the splashscreen also shows this). Please find out the version number before you make asupport call.

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3. Tool Buttons

The tool buttons save you time by enabling you to select some of the mostfrequently used commands, without having to select them from the pull downmenus at the top of the Field window.

3.1. Main Toolbar

The main toolbar is described below from left to right.

New Project (see File menu)Open Project (see File menu)Save Project (see File menu)

Bridge In (see File menu)Import V.10, V.11 Project (see File menu)

Add circuit (see Edit menu)Add board (see Edit menu)Edit (see Edit menu)Delete (see Edit menu)

Network calculations (see Calculations menu)Messages (see Review menu)

Print output (see File menu)Find node reference (see Edit menu)

Help contents (see Help menu)

3.2. Status Bar

The status bar is used for displaying messages about the status of activities inField and for displaying prompts, especially during graphical manipulations inthe Graphics screen. It is highly recommended that you keep an eye on this forimportant prompts when you are performing graphical manipulations such asadding circuits or boards, zooming in, putting a selection fence around items,dragging and copying selections, etc.

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4. Selection of Boards and Circuits

Various activities in Field require you to select one or more branches (boards orcircuits), for editing, deleting, etc. or to select a node (a connection point onboards and circuits), for dragging.

The text list (like any standard extended-selection list box in Windows) allowsyou to:

Select individual branches by clicking the mouse on the list. Select consecutive branches by dragging the mouse over the list. Add or remove individual branches to or from the selection set by

pressing Ctrl and clicking the mouse on the list. Add or remove consecutive branches to or from the selection set by

pressing Ctrl and dragging the mouse over the list.

The graphics window, in its default state, expects you to do one of the following:

Select a node to drag. Select a branch (board or circuit) to drag, copy or edit. Add or remove a branch from a selection set. Start dragging a fence rectangle to select one or more branches. Start dragging a fence rectangle to add one or more branches to a

selection set.

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To select a node to drag, simply move the mouse pointer near to a node at oneor other end of a circuit, and the pointer will snap to the node point. If you pressthe mouse button and drag it, the node will be dragged. If the circuit isconnected to a board at that node, you will be asked whether you wish todisconnect it. If you do not, the drag will be stopped.

To select a branch to drag, copy or edit, simply move the mouse pointer to apart of the circuit or board not too close to the nodes. Click the mouse buttonand the circuit will become highlighted.

To drag the selected branch, press the mouse button again and this time keep itdown while you move the pointer. After the drag is finished, any connected endswill be readjusted so they are still connected. The middle section of a circuitmay be dragged without moving the ends.

To copy the selected branch, hold down the Ctrl key while dragging. Theoriginal branch will be left where it was and a copy will be dragged instead.

To edit the selected branch, double-click it with the mouse or select the Editmenu option or toolbar button.

To add or remove a branch from a selection set, hold down the Ctrl key whileyou select it

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To start dragging a fence rectangle to select one or more branches, press themouse button when the pointer is over a space where there are no branchesand drag it while holding it down. In this example the mouse pointer is draggedfrom the top left of the window:

As you drag the pointer, you will be dragging a rectangular fence. If View >Fence Overlap is turned on, keep dragging the fence until it encloses orintersects all the branches you wish to select. If View > Fence Overlap is turnedoff, the dragged fence must enclose all the branches you wish to select. In thisexample, View > Fence Overlap is turned off and the fence is being dragged toselect nearly all the boards and branches:

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When you have finished dragging the fence, release the mouse button. Theenclosed branches will all be selected and highlighted, as shown below for ourexample:

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Note that the intersected circuits were selected because View > Fence Overlapwas turned on. You may now edit (only if there is only one item selected), ordrag to move or copy the selected items as for a single selection. In thisexample the selection is being dragged to move the selected items:

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To start dragging a fence rectangle to add one or more branches to a selectionset, simply hold down the control key while the fence is being dragged. Unlikeindividual selection with the Ctrl key held down, this cannot be used to removebranches from the selection, only to add them.

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5. Program Size Limits

Field allows up to 3000 circuits, 500 items of distribution equipment, 1000 loadsand 3000 connections of loads to circuits. Up to 10 cable types and 42protective-device types (with 224 individual ratings) can be held in memorysimultaneously; more can be treated but this incurs a speed penalty as data ispaged from disk.

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6. Voltage Drops

Various percentage voltage drops or voltage drop limits are required in the inputdata. This diagram may help to clarify which voltage drops are being set orlimited in the various dialogue boxes:

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7. Customised Schedules

The Review menu has a facility for obtaining customised schedules ofdistribution equipment. All the information required is held in two standard data-files:

citems1.dat contains a complete list of all the items of data available forcustomising your own schedule formats. The items of data are grouped intotypes, and within each group the individual items are given a number. For eachitem of data, information is stored about the format, scale factors, units andheaders to be used if it is included in a customised schedule.

Note this file is strictly formatted and should not be edited.

cforms1.dat contains prepared formats for each customised schedule. For eachschedule, the title is stored, followed by pairs of data types and numbers tospecify each item to be included in the schedule.

See Customised schedule data for more information.

You may modify, add or delete customised schedule formats in cforms1.dat.This may be done directly using any text editor with which you are familiar, butthe preferred method is to use the editing facility provided, which actuallycreates an edited copy of cforms1.dat in the Field folder below your project, sothat the installed customised schedule formats are not lost.

Here are two examples of formats for customised schedules from this file. Youcan see other examples by examining the file, and you can compare some ofthem with the resultant output schedules for the example run):

Design Data

25 0 1 1 1 01, 1, 1, 2, 1, 1, 1, 2, 2, 2, 2, 8, 8, 8, 8, 2, 2, 2, 2, 2, 2, 8, 2, 8, 23, 33, 12, 91, 16, 34,35, 2, 38, 6, 8, 5, 1, 2, 3, 7, 3, 70, 71, 73, 72, 11, 85, 6, 41

Maximum Fault Level (kA) at @ is252Maximum Upstream Earth Loop Impedance (ohm) to @ is265Total Upstream Voltage Drop (%) at @ is242

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Example Schedule:

16 0 0 0 0 01, 1, 1, 2, 2, 2, 3, 3, 3, 2, 2, 2, 5, 5, 5, 51, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 4

Note that the formats are simply placed one after the other in the file, andinclude the three standard schedules (load analysis, design data and installationdata).

The second example is simpler so we shall examine this first:

Line 1 contains the required title, Example Schedule.

Line 2 has 6 numbers indicating how many items required, respectively, in:

Part 1, a table repeated for each circuit on the equipment.Part 2, a continuation table below Part 1 if there are too many items for onetable because of the limited width of the output paper.Total 1, the first of four summary lines for the whole equipment.Total 2, the second '' '' '' '' '' '' '' ''Total 3, the third '' '' '' '' '' '' '' ''Total 4, the last '' '' '' '' '' '' '' ''

In this case, the schedule requires 16 items to be tabulated for each circuit (Part1), but no continuation table (Part 2) or summary lines (Totals 1 to 4). The itemsin Part 1 are to be tabulated under a header which is automatically generatedfrom the data held in file citems1.dat.

Lines 3 & 4 contain pairs of data types and numbers for each item required inPart 1 - the data types on line 3 and the numbers below each data type on line4. E.g. the 6th item in Part 1 is data type 2, CIRCUIT RESULTS, item number 3,Maximum Grouping. (If a Part 2 had also been required, the pairs of data typesand numbers would have followed on from the similar lines for Part 1, and theheader would be generated in a similar way.)

The Design Data schedule is slightly more complicated, having 26 items in Part1, still no continuation table (Part 2), and 3 summary lines (Totals 1 to 3) with 1item each. Totals 1 to 4, being summary lines, are not given a header in thesame way as Parts 1 or 2, so they need an extra line detailing the text which isrequired to precede the items on the line of output. If the text includes the @character it will be replaced by the current board description. The items forTotals 1 to 4 follow this text line.

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8. Calculation Methods

8.1. Load Summation

8.1.1. General

This is done vectorially using input values of W, VA and power factor. For three-phase circuits each phase is summed separately, though for convenience balancedloads are input and output as single values. The third harmonic is summedseparately and carried forward for calculation of neutral current.

8.1.2. Connected Load

The input values of connected load are summed, without spare capacity or diversity,throughout the installation. Power factor is taken into account. Totals, expressed askVA, are output for each final circuit, for each board, and for the completeinstallation.

Secondary summations provide totals of connected load (kVA) under load typeheadings. Quantities of each type of equipment subdivided into type and rating arealso summed. These are output by the Schedules of loads option on the outputmenu.

Any load designated standby is not summed, but is carried to the secondary listingsof loads and shown as standby. Note that the presence of at least one item ofstandby equipment amongst the loads on a circuit effectively makes the whole circuitstandby.

8.1.3. Design Load on Final Circuits

The design load is used to select a device rating and cable size for a circuit. Wheremore than one type of load is connected to a circuit, the contribution from each loadis added into the total design load. The contribution depends on the load type asexplained below.

It is equal to the connected load for lighting, motors, heating, lifts and control panels,but standby equipment is not summed. The standby design load is however used inselecting the device for the circuit and sizing the cable.

For cooking appliances, diversity is applied either in accordance with Table 4A of theIEE Regulations (15th. Edition) or as a percentage of connected load, as directed bythe input in the cooking appliance data.

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For non-classified loads, diversity is applied as a percentage as entered in therelevant data. However, the diversity of elevators must be entered as 100 percent.

For socket circuits, special considerations apply as explained below.

Field is using the old Appendix 5 (now removed) of the 15th. Edition of the IEERegulations and 433-02-04 of BS 7671. The old Appendix 5 says that any of thesocket circuits dealt with (except cooker circuits), and not just the standard A1, A2 orA3 circuits, must have a corrected current-carrying capacity, Iz, not less than In, thedevice rating (multiplied by 2/3 if it is a ring circuit). This appears to mean that thedesign current, IB, must be set equal to In if the old Appendix 9 (now 4) is to beused, as required when the circuit is grouped. Otherwise the use of the alternativeequations in the old Appendix 9 (for groups in which the circuits are not liable tosimultaneous overload) would result in Iz being less than In. When IB is set equal toIn, no matter which old Appendix 9 equation is used, Iz will not be less than In.

In a nutshell, the old Appendix 5 forced IB to be set equal to In. This is probablybecause there is no way to ensure that a socket circuit may not be loaded right up tothe limit imposed by the device rating and seems sensible in normal circumstances.

However, it was only advisory (see old Appendix 5 and old Regulation 314-3, now314-01-03). A circuit could satisfy the old 314-3 without complying with the oldAppendix 5 as long as it satisfied Chapters 43, 46 and 52, and in particular the old433-2 (now 433-02). Although the old 433-2 also said that Iz must not be less thanIn, it referred to the old Appendix 9 where the use of the alternative equations whenthe circuit is grouped may result in Iz being less than In, as long as IB can be safelyassumed to be less than In.

Also, voltage drop depends on IB, and results in larger cables than really necessaryif IB is set equal to In but is unlikely to be as high as In practice.

Unless you specify otherwise, IB is established as follows:

Standard socket circuits (A1 (433-02-04); A2, A3 (Appendix 5, 15th. Ed.)):

IB = In

Other socket outlets - depends on the mix of loads on the circuit:

2A sockets: IB = connected load, subject to minimum 0.5A per socketOther ratings, one socket only: IB = socket ratingOther ratings, more than one socket: IB must be set by userOther ratings, non-socket loads included as well: IB must be set by user

To get a realistic cable size for voltage-drop considerations simply enter a realisticvalue of IB for Fix IB for Voltage-Drop Calculations on the input data for the circuit.This will not affect the value of IB used in the current-carrying capacity calculations.

If IB must be set, or if you want to set it anyway since the circuit is grouped withother circuits not liable to simultaneous overload and IB can be safely assumed to beless than In, enter a realistic value of IB for Fix IB for Voltage-Drop Calculations as

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above, but also enter Yes for Fix IB Also for Grouping. Also you must ensure that thepredefined circuit being used has No for Use Equation 2 of Appendix 4.

The aggregate rating of all sockets on a circuit is calculated and included on outputto assist the user to determine design load, but the aggregate is not summed beyondthe final circuit.

The contribution to the design load of the upstream distribution circuit is determineddifferently when socket circuits are involved - see Load summation – design load ondistribution circuits.

8.1.4. Design Load on Distribution Circuits

At each board the sum of the design loads of outgoing circuits, plus spare capacitywhere appropriate, is multiplied by the diversity. The values are output in kVA andpower factor for each distribution circuit and for the complete installation.

However, when one of the outgoing circuits is a final socket circuit, the contributionof the sockets to the design load of this circuit (see Load summation – design loadon final circuits) is not included in the summation.

This is because this is normally set equal to the device rating (multiplied by 2/3 for aring circuit) to ensure that the cable is protected no matter what load is drawn fromthe sockets, but this would be an unrealistically high load to carry up to thedistribution equipment. Instead, the socket loading as given in the socket data isincluded, assuming that it includes an allowance for diversity.

8.1.5. Design Current

This is calculated from the design VA divided by the nominal voltage of the supply.When the supply is three-phase, the line voltage is used throughout, with the factor√3 applied to single-phase circuits: so for a 400V supply the single-phase voltage istaken as 230.94V and current values are slightly different from those calculated at230V. For single-phase supplies the input phase/neutral voltage is used throughout.

For distribution circuits the design current is derived from the design load. In thecase of TPN circuits with unbalanced load, the highest phase current is used for allsubsequent calculations.

8.1.6. Neutral Current

For TPN circuits with unbalanced load, this is derived as follows:

Any third harmonic component is subtracted from each phase. The fundamentalcurrents are resolved vectorially, allowing for power factor. The third harmoniccurrents are resolved vectorially, allowing for power factor. The resultant

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fundamental and third harmonic currents are summed arithmetically and the thirdharmonic component expressed as a percentage of the total.

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8.2. Device Selection/Checking

8.2.1. Basic Factors

The type of device must be selected. However, the rating does not have to beentered. If it is not entered, Field selects it; otherwise, Field checks it.

To select or check the device rating, the following criteria are used:

Circuit design current Starting or inrush current (final circuits only) Discrimination with each downstream device under overload conditions.

The selected rating will satisfy as many as possible of these criteria. A warning orerror will be given if it is not possible to select a rating to satisfy all the criteria, or ifthere is inadequate data to select a rating.

Later, when the cable sizing calculations are carried out, further checks are madethat the device will also discriminate with each downstream device under faultconditions, and have a sufficiently high breaking capacity for the fault current or areprotected by the upstream device. See the later sections on short-circuit and earth-fault calculations.

8.2.2. Design Current

Field attempts to satisfy BS 7671 regulation 433-02-01(i) so that the nominal currentor setting of the device is not less than the design current of the circuit. The ratingmargin in the Design Data is used so that the nominal current or setting of the deviceis not less than the product of design current and rating margin.

8.2.3. Starting Current

For a circuit with one cage induction motor and GEC BS88 fuse, selection will be inaccordance with the Tables in 10.1.3 Protective device data – device selection onmotor circuits when a standard starting condition has been input.

For a circuit with one cage induction motor, GEC BS88 fuse and non-standardstarting data, Field does not attempt to ensure that the rating it selects will cope withstarting current. In a future version of Field, reference will be made to the pre-arcingtime/current characteristics of the fuses. The selected rating will be that whosecharacteristic passes through or above the coordinate given by the motor maximumstarting current/duration.

For all other cases the user must set the rating.

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8.2.4. Inrush Current

You may input s-factors for an analysis or use your firm's default data. SeeProtective device data – s-factors for details of how to modify the default data.

Lighting is used here as an example of the application of s-factors, but the principlealso applies to heaters, cookers and control panels. The total number of each type oflamp is determined. The total current demand of each group of a lamp type andassociated control equipment is multiplied by the appropriate s-factor. The selectedrating must be greater than the sum of the resultant values. This can be representedby:

In = Sa.Ia + Sb.Ib +

Where In = nominal rating of deviceSa, Sb, ... = s-factor for lamps type A, B etc.Ia, Ib, ... = total circuit current for all lamps type A, B etc.

For some other load types, or where no s-factor has been input, Field will haveinsufficient data to ensure that the rating it selects will cope with the inrush current orto check the rating if set by the user.

8.2.5. Discrimination

Where adequate data are available a rating will be selected to discriminate with alldownstream devices.

Discrimination is determined in two ways:

a) By reference to tables of predetermined relationships between various ratings(see Protective device data – discrimination between fuses).

b) By comparison of time/current characteristics. This is primarily used to comparecurves of different device types, but will work for any combination of types andratings. If the two curves cross or the margin of discrimination is less than 25%,the rating for the upstream device is increased. Where devices have aninstantaneous trip current, such as MCB's, the curves are only compared as faras the instantaneous trip current of the downstream device; this avoidsincreasing the rating unnecessarily when two curves will inevitably cross, as witha fuse discriminating against an MCB. A check is later made that the intersectioncurrent is above the maximum prospective short-circuit current at that level in thenetwork.

Where insufficient data are available, Field will not attempt to ensure that the rating itselects is adequate for discrimination.

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8.2.6. Standard Circuits

Field is using 433-02-04 and the old Appendix 5 (now removed) of the 15th. Editionof the IEE Regulations. For standard circuits type A1 from 433-02-04 the rating isselected at 30 or 32A to conform to 433-02-04. For standard circuits, type A2 or A3from the old Appendix 5, the rating is selected to conform to Table 5A. If the userhas set the design load a warning will be given if it exceeds the rating (with ratingmargin fixed at 1.0), but no other checks are made.

8.2.7. Ratings Set by User

Where the rating has been set by the user, a warning will be given if it does notsatisfy all the criteria for rating selection, or if Field has inadequate data to make acheck.

8.2.8. Fused Connection Units

At present Field does not select the BS1362 fuse rating to account for the designcurrent and starting or inrush current of the load, or discrimination with any device inthe equipment.

8.2.9. Socket Circuits

This applies to socket circuits which are not standard circuits type A1, A2 and A3(433-02-04 and Appendix 5, 15th. Edition). Where only one socket outlet isconnected and the device type set by the user includes a rating equal to that of thesocket outlet, Field will select that rating. For all other cases the user must set therating.

8.3. Cable Sizing/Checking

8.3.1. Basic Factors

The cable-sizing checks for each circuit use the following criteria:

a) Current-carrying capacity of the cable.b) Voltage drop within the circuit.c) Overall voltage drop at the load end of the circuit.d) Short-circuit conditions.e) Earth-fault conditions.

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The checks proceed in the above order. The selected size and number will satisfy asmany as possible of these criteria, provided that Field keeps the cable size ornumber of parallel cables within the appropriate limits.

The type of cable for each circuit can be entered, but not the cable size or thenumber of parallel cables. However, maximum and minimum limits for these valuescan be entered or left as zero. To fix the size or number, the size may be entered forboth the maximum and minimum limits; Field is then constrained to use that value forthe size or number.

Of course, cable sizes are also limited by the maximum and minimum sizes availablefor the cable type concerned (installation method, phase, number of cables andnumber of cores per cable are taken into account). Also, for certain standard circuittypes (A1, A2 or A3 final circuits) there are limits laid down in 433-02-04 andAppendix 5, IEE 15th. Edition.

Finally, parallel cables are NOT allowed in these special circuits or in ring circuits, sothe number of cables is limited to one.

If the cable-sizing check for a particular criterion is satisfied, it moves on to the nextcriterion. Otherwise the following occurs:

The next available size is chosen if possible and the checks restart atcriterion (a).

Otherwise if the number can be increased (and if it would help) it is increasedby one (the size is usually set back to the value determined for the previouscriterion) and the checks restart at criterion (a).

Otherwise an error or warning message is given.

(An error or warning message will also be given if there is inadequate data to checkthe criterion.)

The checks finish when an adequate size and number are found which satisfy all thecriteria or the limits are finally reached and the error or warning message is given.

Other calculations are also made to select or check the length of the cable and thesize and length of each conductor comprising the CPC.

No attempt is made to resize a cable to satisfy criterion (c), since this requires theuser to make a decision about whether to increase the size of this cable or that ofone of the upstream distribution cables. The length of a final circuit, however, if notset by the user, will be calculated in order to satisfy criterion (c).

The cable may be resized to satisfy criterion (e), i.e. to withstand the earth-faultcurrent, but the only CPC conductor that will be resized for this criterion is a separatecable used as the CPC or as part of the CPC. This is sized to withstand the earth-fault current (or the relevant proportion thereof). The user must fix other CPCconductor sizes.

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8.3.2. Current-carrying Capacity

The basic current (In) used to select the cable sizes is set equal to the device ratingfor a radial circuit, and to 2/3 of the device rating for a ring circuit. For a final circuitconnected to a single motor, with overcurrent trip, In is set equal to the current atwhich the trip will operate.

The circuit design current (IB) is set equal to In for a standard type A1, A2 or A3 finalcircuit (433-02-04 and Appendix 5, 15th. Edition), and otherwise to the calculateddesign current for the circuit or the value set by the user.

Appendix 4 of BS 7671 gives equations for the sizing of cables with regard tocurrent-carrying capacity for normal and overload conditions.

Field usually uses a generalised equation:

Equivalent to equations (1), (2), (5) or (6), but is referred to as equation (2)for convenience:

(2) It >= In FFCa Ci Cg 1.45

Where FF is the fusing factor (normally 1.45, but 2 for BS3036 fuses), and Ca, Ciand Cg are correction factors for ambient temperature, thermal insulation andgrouping.

However, if the circuit is grouped with other circuits and they are not liable tosimultaneous overload, Appendix 4 of BS 7671 allows the use of alternateequations. In this situation Field uses two generalised equations:

Equivalent to (3) or (7), but referred to as equation (3) for convenience:

(3) It >= IBCa Ci Cg

Equivalent to (4) or (8), but referred to as equation (4) for convenience:

(4) It >= 1 ( In² FF² + IB² 1 - Cg²)1.45 Ca Ci Cg²

In and IB are used as in Appendix 4 of BS 7671 to calculate the corrected current-carrying capacity (equation (2), or the more stringent of equations (3) and (4), asrequested by the user). This is then used to select the smallest cable of the requiredtype and installation method with the required capacity.

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8.3.3. Circuit Voltage Drop

This is only performed if the maximum length is known (see Cable sizing/checking –maximum length).

The voltage drop in the circuit is calculated from the tabulated resistive and reactivevoltage drops (mV/Am, for the cable, phase and installation method), its length (asset by the user for the voltage drop calculation), the design current IB, the powerfactor and the nominal voltage.

The tabulated resistive voltage drop is corrected for temperature (Appendix 4,equation (10), BS 7671). With the reactive component it constitutes a temperature-corrected vector. The scalar product of this vector and the vector for the designcurrent IB and power factor is the magnitude of the resultant voltage drop per metre.This is multiplied by the length and 100 and divided by the nominal voltage to get thepercentage circuit voltage drop. (This is a more explicit statement of Appendix 4,section 7.3, of BS 7671.) Since the tabulated three-phase values are for balancedcircuits, the neutral current is included if the circuit is unbalanced. If the circuit is froma busbar the contributions from the resistance and reactance per metre of the liveand neutral conductors in the busbar and the currents in each section of the busbaras it changes between take-off points are added to the cable voltage drop. Atpresent the power factor of the current in each busbar conductor is not calculated,but it is assumed to be lined up with the phase angle of the busbar conductor'simpedance, so that, effectively, no power factor correction as mentioned in BS 7671takes place.

The final voltage drop in the circuit is compared to the limit value, and if this isexceeded the cable size is increased to the next available size and the exercise isrepeated until this criterion is satisfied, if possible. Overall voltage drop is calculatedby adding up all the resistive and reactive contributions separately, and taking thescalar product of the resultant voltage drop vector with the current. This is only usedfor checking cables, not for sizing them (see Cable sizing/checking – basic factors).

8.3.4. Short Circuit

This calculation is performed in two main stages:

A) Calculate minimum short-circuit current, i.e. at load end of circuit, and check thecable can withstand the energy generated until the device disconnects.

B) Calculate maximum short-circuit current, i.e. at supply end of circuit, and checkthat this is less than the breaking capacity of the device if it is an instantaneoustrip device, and that each parallel cable can withstand the energy let-through ofthe device and upstream device.

Both stages are skipped if the device is not a BS88 or other HRC fuse or aninstantaneous trip device, and a suitable warning is given.

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The cable resistance is obtained from the relevant table in Conductor data -impedances and corrected to a particular temperature depending on the calculation,either minimum temperature, running temperature or mean fault temperature (i.e. themean of the running temperature and the maximum permitted final operatingtemperature). The relevant resistance-temperature coefficient for the conductormaterial is used to obtain the correction factor.

The reactances are obtained from the relevant table in Conductor data -impedances. If no reactance is available in the table, then for a cable over 35 mm² itis calculated assuming an inductance of 0.2 mH/km (zero for smaller cables).

If the circuit is from a busbar the resistances and reactances of the sections of thebusbar live and neutral conductors from the end-feed to the circuit take-off areincluded.

The k-factors are obtained from the cable database. When inputting the data, theuser either set these values explicitly or used the default values calculated from thenormal and final operating temperatures. Details of this calculation are given inCable sizing/checking – k-factors.

Stage (a) is only performed if the maximum length is known (see Cablesizing/checking – maximum length).

The maximum short-circuit impedance at the load end of the cable is first calculatedby adding vectorially the circuit impedance to the overall upstream impedancealready calculated (calculations start at the supply and work down to the finalcircuits). The upstream impedance is at normal running temperature and the circuitimpedance is at the mean fault temperature (see Appendix 17 of the IEERegulations, 15th. Edition). The minimum possible fault current is then calculatedfrom this value (it also depends on the circuit phase). If the device is aninstantaneous trip device and the current can trip it instantaneously the rest of stage(a) is skipped. Otherwise Field checks that the cable can withstand this current untilthe device trips, resizing if necessary and possible. If the trip time exceeds 5 s thecheck is made against the 5 s point on the characteristic curve. If it is less than 0.01s the cable is checked against the energy let-through of the device (as supplied bythe manufacturer) instead of the calculated value of current squared x trip time.

Stage (b) calculates the minimum short-circuit impedance at the supply end of thecable, and hence the maximum short-circuit current. This does not depend on thecable, only on the upstream impedances (corrected to the minimum expectedambient temperature during short circuit). The calculation now depends on the typesof the device and the one upstream:

For BS88 and other HRC fuses, the disconnect time is obtained. If this is lessthan 0.1 s Field checks that the cable can withstand the energy let-through ofthe fuse (data from manufacturer), resizing if necessary and possible. If thecable is paralleled Field checks that each cable can withstand the minimumshort-circuit current at the supply end of the cable until the fuse disconnects,resizing if necessary and possible. This current is merely due to the upstreamimpedance at normal running temperature with no contribution from thiscircuit.

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For instantaneous trip devices with an upstream fuse, the maximum short-circuit current is checked to see whether it exceeds the breaking capacity ofthe device. If so, and the intersection current also exceeds the breakingcapacity of the device, the calculation stops with a warning. Otherwise Fieldchecks that the cable (or each parallel cable) can withstand the intersectioncurrent or the maximum short-circuit current, whichever is smaller, until theinstantaneous trip occurs, resizing if necessary and possible, and that thecable can withstand the energy let-through of the upstream fuse(manufacturer's data), resizing if necessary and possible.

For instantaneous trip devices with a similar device upstream, the maximumshort-circuit current is checked to see whether it exceeds the breakingcapacity of the device (as above). If so, the calculation stops with a warning.Otherwise Field checks whether the cable (or each parallel cable) canwithstand the maximum short-circuit current until the device trips, resizing ifnecessary and possible, and if the upstream device is also current-limiting itchecks whether the cable (or each parallel cable) can withstand the energylet-through of the upstream device (data from manufacturer), resizing ifnecessary.

8.3.5. Earth Fault

This calculation is only performed if the maximum length of circuit is known (seeCable sizing/checking – maximum length).

The size, and resistance and reactance (per metre), of the protective conductor areobtained differently for each conductor type (all resistances are now calculated atnormal running temperature):

For steel armour, the resistance, given the phase conductor size and numberof conductors, is obtained from the relevant table in Conductor data -impedances. The reactance is assumed to be 0.3 m/m. The minimumarmour size is calculated from the resistance using the resistivity of steel. Awarning is given if any other type of insulation is present or if the armour isaluminium.

For copper sheath on mineral-insulated cables, the relevant table inConductor data - impedances gives the maximum resistances for light &heavy duty cables. The reactance is assumed to be 0.3 m/m. The minimumsize of the sheath is calculated from the resistance using the resistivity ofcopper.

For a core of the cable the size is obtained using BS6004 if this applies. Ifnot, or if it does not cover the required phase conductor size, the user iswarned and asked to set a size. The resistance and reactance are thenobtained as for a phase conductor.

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For a separate cable the size is selected by trying each available size,starting with the smallest, until one is found that can withstand the earth faultcurrent (or part thereof if in parallel), unless the size has already been set bythe user. The resistance and reactance for each size are obtained as for aphase conductor.

For conduit the impedance is obtained from the relevant table in Conductordata - impedances. It gives two ranges of earth-fault current, so thecalculation is repeated if the fault current turns out to be in the range notassumed initially. The impedance is assumed to be entirely resistive, i.e. thereactance is assumed to be zero.

The minimum conduit diameter is obtained from a simple use of Appendix 12 of theIEE Regulations, 15th. Edition (subject to the overall minimum in the Design Data)unless already set by the user. The slight possibility of using a smaller conduit forshort straight runs has been discounted by ignoring Tables 12A and 12B. BecauseField needs the minimum possible conduit diameter (worst case for trip time andthermal requirements) it is only necessary to use the four conduit factors from Table12D representing 3.5 m straight runs. The total cable factor is calculated from Table12C, taking into account the number of cables in the circuit, whether the circuit is aring, and any necessary paralleling of cables. No account is taken of other circuitssharing the conduit because only the minimum diameter is required. A warning isgiven if the cable exceeds 10 mm² or is not single-core. The conduit whose conduitfactor exceeds the total cable factor is chosen.

For trunking the dimensions entered by the user are used. Field makes noattempt to size trunking (c.f. conduit above) because it often containsmulticore cables, is shared by other circuits or contains partitions, so thecalculated values would be too pessimistic. The resistance is calculated fromthe resistivity of the material (steel or aluminium) and the given size. Thereactance is assumed to be zero.

The resistances are corrected to a particular temperature depending on thecalculation, the minimum temperature or the running temperature. Note that therunning temperatures are not usually the same as for the phase conductor. If notprovided in the cable database the running temperature is assumed to be 10 C lowerthan that of the phase conductors for armour or sheath, halfway between that of thephase conductors and 30 C for conduit or trunking, and 30 C for separate cable. Theresistance-temperature coefficient relevant to the protective conductor material isused to obtain the correction factor.

Combinations of protective conductors are dealt with by adding resistances andreactances in series or parallel as required.

If the circuit is from a busbar the resistances and reactances of the sections of thebusbar live and earth conductors from the end-feed to the circuit take-off areincluded.

The k-factors are obtained from the cable database. When inputting the data, theuser either set these values explicitly or used the default values calculated from the

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normal and final operating temperatures. See Cable sizing/checking – k-factors fordetails of this calculation.

The calculation process involves several passes for each circuit.

On the first pass, resistances, reactances and k-factors are obtained for eachparallel or serial conductor making up the protective conductor. Then the earth-faultimpedance at running temperature is calculated for the circuit and added vectoriallyto the upstream impedance. The corresponding earth-fault current is calculated.Note that the open-circuit voltage at the transformer is now used for calculating thecurrent, as specified in BS 7671 Amendment 1. This is rather arbitrarily set to240/230 times the nominal phase voltage, so that for a phase voltage of 230V theopen-circuit voltage is 240V. If the device is an instantaneous trip device and thecurrent is large enough to cause instantaneous tripping, the rest of this calculation isskipped.

On the second pass, the current passing through each conductor, including thephase conductor, is determined from the relevant impedances and the overallcurrent, and then each conductor is checked for the ability to withstand this currentuntil the device trips. If the trip time is greater than 5 s the check is made against the5 s point on the characteristic curve. If the trip time is less than one half-cycle thecable is checked against the energy let-through of the device (data frommanufacturer) instead of the calculated current squared x trip time.

Further passes may be necessary if the first size tried for the separate cable CPCproves to be inadequate. In this case the next higher size is selected and theprocess starts again.

8.3.6. Indirect Contact

See Section 413 of BS 7671. Field makes various assumptions about what meansare to be used for protection against electric shock (see Chapter 41). It assumes thatSection 412 (Protection against Direct Contact) and Section 413 (Protection againstIndirect Contact) are to be used rather than Section 411 (Protection against bothDirect and Indirect Contact). It also assumes that in Section 413, the method to beused is that found in Regulation 413-02 (Protection by earthed equipotential bondingand automatic disconnection of supply) rather than Regulations 413-03 to 413-06.The reasons for these assumptions are that Section 411 and Regulations 413-03 to413-06 are outside the scope of Field or do not require the same level of detailedcalculation. If the assumptions are incorrect, any warnings related to Regulation 413-02 may be ignored.

The calculations required by Regulation 413-02 depend on the system of earthing(see 413-02-01). Calculations for TT and IT systems are not yet available (a warningis given to this effect). For TN systems, the procedure is as follows:

Final circuits not feeding fixed equipment - the disconnection time due to theearth fault current at normal running temperature is checked against the timelimit obtained using Table 41A (see 413-02-09). If this check fails, the

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disconnection time is checked against the 5s limit and the CPC impedancebetween the load and the nearest equipotential bonding is checked against alimit (see Table 41C) intended to limit the fault potential to 50V (see 413-02-12). If these checks fail as well, a warning is given and the user is referred to413-02-15.

Other final circuits and distribution circuits - the disconnection time ischecked against the limit of 5s (see 413-02-13). If this check fails, a warningis given and the user is referred to 413-02-15.

When all the circuits on a board have been checked a further check is made:

If at least one final circuit on the board satisfied the 413-02-09 check (see Table41A), and at least one other satisfied the 413-02-13 check (5s) but had a longerdisconnect time than Table 41A would have allowed, then the latter part of 413-02-13 must be satisfied. In this case, the CPC impedance from the board to theequipotential bonding is checked against a limit (see Table 41C) intended to limit thefault potential to 50V. If this check fails, the user is warned that, unless the user editsthe data to decrease the CPC impedance, Field is assuming that additionalequipotential bonding is made at the board (see 413-02-13). Since this means thatdownstream circuits that may have failed to satisfy 413-02-12 may now satisfy it, thecalculations for all of the downstream circuits (including those fed by furtherdownstream boards) are repeated.

8.3.7. Maximum Grouping

Whether or not the grouping has been set by the user, Field attempts to calculate themaximum grouping. Equation (2) or Equations (3) and (4) of BS 7671 Appendix 4are inverted to obtain a minimum value of the grouping derating factor for the cablesize and currents. This is used to obtain a maximum grouping from BS 7671 Table4B1 or 4B2.

8.3.8. Maximum Length

If the maximum length has not been set for distribution circuits Field gives an errorand stops the calculation. For final circuits Field calculates this length by invertingthe calculations so that maximum lengths are calculated for the size selected so far.Those calculations that do not depend on the length (such as sizing for current-carrying capacity and checking that the cable can withstand the maximum short-circuit current at the supply end of the circuit) will still be carried out as usual.

8.3.9. k-factors

These are either entered directly when adding new cable data to the database or thedefault values are used. The default values are calculated from the normal and finaloperating temperatures using the equation provided on page 87 of Commentary on

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the 15th Edition of the IEE Wiring Regulations by B.D. Jenkins, published by PeterPeregrinus Ltd. on behalf of the IEE. This simplifies to:

k = A √ ln ( 1 + Tf-Ti )B+Ti

where Ti and Tf are the normal and final permitted conductor operatingtemperatures, and A and B are physical constants for the conductor, with thefollowing values (Ti and Tf are given in terms of the live conductor values, TI and TF,or the armour/sheath values, ATI and ATF, stored for the cable):

Conductor function Ti (°C) Tf (°C)Live or CPC core TI TF *Armour/sheath ATI ATFCPC cable 30 TF *Conduit/trunking (TI+30)/2 TF

Conductor material A B (°C)Copper 226 234.5Aluminium 148 228Steel/lead 42 230Steel 78 202

* The Regulations assume a different final permitted temperature for PVC-insulatedcables above 300 mm², but Field will account for this by assuming that it is TF-20.

Note that the use of this equation results in k-factors identical to those given in Table43A and Tables 54B to 54F of the Regulations, but is more general.

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9. Standard Data Used in the Program

Field accesses many sets of standard data for use in the calculations. Most ofthese are in files. They include data about devices, cables, protectiveconductors, motors, etc. Some files can be modified to suit the practice in yourcompany, subject to the appropriate authorisation. E.g., the data fordiscrimination between fuses may be edited in the file pddisc1.dat.

Field can also add data about devices or cables to the database files (held inthe area required by IES programs for user's data files).

To copy devices or cables developed by other users, you can use the Copyoptions under the Edit Database option.

9.1. Protective Device Data

9.1.1. Standard Data

These are all held in two files, pdref.dat and pdrat.dat. There are too many devicesto list here, but you can examine pdref.dat using Notepad or any other text editor– itis a simple list of device names and descriptions, with one line per device. The listincludes devices with fixed curves and adjustable curves. These may be edited, andnew devices may be added. See the separate document, The Field device databaseeditor (Fielddb.exe) for details. This is in a file called Field Device Database EditorUser Guide.

9.1.2. Discrimination Between Fuses

The fuse discrimination relationships, based on the GEC I²t characteristics inPublication IEF/401, 1983, are held in the global data file pddisc1.dat. Data for typeNIT and T fuses are combined to cover any combination of these types. If your fusesdiscriminate differently you can deal with this by editing the file. The data is shownbelow.

Downstream2 4 6 10 16 20 25 32 35 40 50 63 80 100 125 160 200 250 315 355 400 450 500

Upstream4 6 10 20 25 32 35 40 50 63 80 125 160 160 200 250 315 400 450 560 630 670 750

Downstream560 630 670 710 750 800 1000 1250

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Upstream800 1000 1250 1250 1250 1250 - -

9.1.3. Device Selection on Motor Circuits

A starting envelope is used within Field to ensure protection of motor circuits; thisenvelope is dependent upon motor size and starting method, as defined below (seealso Protective device data – BS1362 fuses):

Starting Method Motor Rating (kW) Maximum Current (A) Maximum Time (s)1 5 x FLC 51.1 – 75 7 x FLC 10

Direct on Line

75 6 x FLC 151 2.5 x FLC 20Assisted Start

(SD, SDN & AT) 1 3.5 x FLC 10

9.1.4. BS1362 Fuses

For single-phase motors up to and including 0.55 kW select 13A fuses.

For motors exceeding 0.55 kW fuse rating cannot be selected or checked and asuitable warning will be given.

9.1.5. s-factors

S-factors have default values when a new project is started. You may wish to modifythese to suit your requirements, by editing them in the Design Data dialogue box.

The values must be chosen to suit the type and quantity of load and the type ofdevice usually used with that load. Manufacturer's data for the loads and the deviceswill be useful.For a particular load type and quantity, the s-factor is multiplied into the design loadfor that load type and quantity. The rating for the device is then chosen so that itexceeds this product (see example in Calculation methods). The s-factor thereforerepresents the effect of the inrush current envelope on the device selection. Theproduct of design current and s-factor is not intended to represent the real inrushcurrent. S-factors will always be at least 1 if the inrush current is insignificant, and atmost about 5 for loads with very heavy inrush currents. Usually the s-factors for aload type will decrease with increasing quantity because the inrush currents will tendto spread out in time.

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9.2. Conductor Data

9.2.1. Cable Types

At present the cable types listed below are available. Field already has data on thecables from Appendix 4 of BS 7671, and a few others. This list can be easilyextended by entering your own types or editing existing types using Database > Edit.

Cable Type Relevant BS 7671 Table from Appendix 4

CPS 4D1A,BCP90S 4D1A,B (columns 2 to 5 only)CPM 4D2A,BCPAS 4D3A,BCPAM 4D4A,BCTS 4E1A,BCTM 4E2A,BCTAS 4E3A,BCTAM 4E4A,BR85S 4F1A,BR85M 4F2A,BR60SFC 4H1A,B using single-core valuesR60MFC 4H1A,B using multicore valuesR85SFC 4H2A,B using 85°C correction factors (single-core data)R85MFC 4H2A,B using 85°C correction factors (multicore data)R150SFC 4H2A,B using 150°C correction factors (single-core data)R150MFC 4H2A,B using 150°C correction factors (multicore data)R60FCD 4H3A,B using 60°C rubber correction factorsR85FCD 4H3A,B using 85°C rubber correction factorsR150FCD 4H3A,B using 150°C rubber correction factorsG185FCD 4H3A,B using 185°C glass-fibre correction factorsPFCD 4H3A,B using 60°C PVC correction factorsP90FCD 4H3A,B using 90°C PVC correction factorsM70LS 4J1A,B using light-duty single-core values, and 0.9 factorM70H 4J1A,B using heavy-duty single-core values, and 0.9 factorM70LM 4J1A,B using light-duty multicore values, and 0.9 factorM70HM 4J1A,B using heavy-duty multicore values, and 0.9 factorM70PLS 4J1A,B using light-duty single-core valuesM70PHS 4J1A,B using heavy-duty single-core valuesM70PLM 4J1A,B using light-duty multicore valuesM70PHM 4J1A,B using heavy-duty multicore valuesM105LS 4J2A,B using light-duty single-core valuesM105HS 4J2A,B using heavy-duty single-core valuesM105LM 4J2A,B using light-duty multicore valuesM105HM 4J2A,B using heavy-duty multicore valuesAPS 4K1A,BAPM 4K2A,BAPAS 4K3A,B

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APAM 4K4A,BATS 4L1A,BATM 4L2A,BATAS 4L3A,BATAM 4L4A,BCXS - (manufacturer's data)CXM - (manufacturer's data)CXAS - (manufacturer's data)CXAM - (manufacturer's data)CLAM - (manufacturer's data)TCC - (manufacturer's data)CPMT&E - (manufacturer's data)PYM70LM - (manufacturer's data)PYM70PLM - (manufacturer's data)PYM70HM - (manufacturer's data)PYM70PHM - (manufacturer's data)PYM70HS - (manufacturer's data)PYM70PHS - (manufacturer's data)LSX - (manufacturer's data)LSOHCW - (manufacturer's data)LSOHAS - (manufacturer's data)LSOHAM - (manufacturer's data)

The references are usually constructed as follows:

Conductor + Insulation + Armour + Single/Multicore + Miscellaneous

C Copper (assumed if left blank)ConductorA AluminiumP 70°C PVC (general purpose)P90 90°C PVC (heat-resisting)T ThermosettingR60 60°C RubberR85 85°C RubberR150 150°C RubberG185 185°C Glass fibreM70 70°C Mineral, bare, exposed to touchM70P 70°C Mineral, PVC coveredM105 105°C Mineral, bare, not exposed to touchX XLPE

Insulation

PA PaperA Armoured (multicore: steel; single-core: aluminium)L Light-duty Copper (only applies to mineral-insulated)

Armour

H Heavy-duty Copper (only applies to mineral-insulated)S Single-coreSingle/MulticoreM Multicore (assumed if left blank for flexible cords)FC Flexible cableMiscellaneousFCD Flexible cord (always multicore)

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9.2.2. Impedances

This data is all held in the global data file cables1.dat, which can be examined with atext editor such as Notepad.

In general, zeroes in the data are values that are unavailable or not found yet, andmay result in warnings from Field if it tries to use them.

If you get any of these warnings and you have the relevant data, judicious editing ofthis file may be undertaken to eliminate them.

9.2.3. Motor Data

This data is all held in the global data file motors1.dat, which can be examined with atext editor such as Notepad.

In general, zeroes are values that are unavailable, and if Field tries to use them it willproduce warnings.

If you have the relevant data, judicious editing of this file can be undertaken toeliminate them.

9.2.4. Customised Schedule Data

9.2.4.1. Available Variables

The items of data available for customised output are held in the standard data filecitems1.dat. See Customised Schedules for details of how to make use of this data. A list ofthe items is given below, grouped by data type. See the file itself for the widths of each item(immediately after the item number) if you are unsure whether your schedule format will fitinto the limit of 132 characters for the output file. Note items marked with a * are of internalsignificance only.

Data Type 1 - Circuit Input Data (Use Anywhere In Schedules)

Circuit Number *Supply Equipment Number *Way NumberEquipment Number *Predefined Circuit Number *Predefined Cable Number *Predefined CPC Number *Maximum Number of Parallel CablesMinimum Number of Parallel CablesCPC TypeCPC Trunking MaterialRing or RadialUser-Fixed Design Current IB (A)Route Length (m)

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Effective Route Length for Voltage Drop Calculation (m)Length to Busbar Take-off (m)Maximum Cable Size (sq.mm)Minimum Cable Size (sq.mm)Ambient Temperature (C)Thermal Insulation Derating factorOverall Voltage Drop Limit (%)Circuit Voltage Drop Limit (%)CPC Core Size (sq.mm)CPC Cable Length (m)CPC Cable Size (sq.mm)CPC Conduit Length (m)CPC Conduit Diameter (mm)CPC Trunking Length (m)CPC Trunking Size (sq.mm)User-Fixed Device Rating (A)Circuit DescriptionPhaseCable TypeInstallation MethodCPC Cable TypeTrunking Dimensions or ReferenceDevice TypeGroupingCommentsAppendix 4 Equation 2 Used?User-Fixed Design Current IB for Voltage Drop Calculation?User-Fixed Design Current IB for Grouping Calculation?Essential Sub-Circuit Contactor?

Data Type 2 - Circuit Results (Use Anywhere In Schedules)

Circuit Number *Number of Parallel Cables in CircuitMaximum GroupingGrouping if IB < 0.3 IzProtective Device Status *Cable Status *CPC Status *Cable Size CriterionConnected Load (R) (kVA)Connected Load (Y) (kVA)Connected Load (B) (kVA)Connected Load (N) (kVA)Design Load (R) (kVA)Design Load (Y) (kVA)Design Load (B) (kVA)Design Load (N) (kVA)Power Factor (R)Power Factor (Y)Power Factor (B)Design Load (kVA)Design Load (kW)Power FactorThird Harmonic Current (R) (A)Third Harmonic Current (Y) (A)

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Third Harmonic Current (B) (A)Third Harmonic Current (N) (A)Third Harmonic Power Factor (R) (A)Third Harmonic Power Factor (Y) (A)Third Harmonic Power Factor (B) (A)Aggregate Rating (A)Largest Device Rating on Equipment (A)Maximum Cable Length (m)Maximum CPC Cable Length (m)Maximum CPC Conduit Length (m)Maximum CPC Trunking Length (m)Phase Conductor K FactorSelected Conduit Diameter (mm)Selected Cable Size (sq.mm)CPC Core Size (sq.mm)CPC Cable Size (sq.mm)Circuit Voltage Drop (%)Total Voltage Drop (%)Circuit Earth Fault Impedance Limit (ohm)X-Ray Earth Fault Impedance Limit (ohm)Load End Short-Circuit Resistance (ohm)Load End Short-Circuit Reactance (ohm)Minimum Supply End Short-Circuit Impedance (ohm)Maximum Supply End Short-Circuit Current (kA)Maximum Load End Short-Circuit Impedance (ohm)Minimum Load End Short-Circuit Current (kA)Minimum Load End Short-Circuit Impedance (ohm)Maximum Load End Short-Circuit Current (kA)Device Energy Let-Through at Maximum Supply End Short-Circuit Current (A2s)Device Energy Let-Through at Minimum Load End Short-Circuit Current (A2s)Device Energy Let-Through at Minimum Supply End Short-Circuit Current (A2s)Disconnection Time at Maximum Supply End Short-Circuit Current (s)Disconnection Time at Minimum Load End Short-Circuit Current (s)Disconnection Time at Minimum Supply End Short-Circuit Current (s)Cable Energy Withstand (A2s)Circuit Phase Earth Fault Impedance (ohm)Circuit CPC Earth Fault Impedance (ohm)Total CPC Earth Fault Impedance (ohm)Load End Earth Fault Resistance (ohm)Load End Earth Fault Reactance (ohm)Load End Earth Fault Impedance (ohm)Load End Earth Fault Current (kA)Device Energy Let-Through at Load End Earth Fault Current (A2s)CPC Energy Withstand (A2s)Disconnection Time at Load End Earth Fault Current (s)Grouping Derating FactorAmbient Temperature Derating FactorBreaker Type Derating FactorThermal Insulation Derating FactorCable Resistive Voltage Drop (mV/Am)Cable Reactive Voltage Drop (mV/Am)Tabulated Current-Carrying Capacity (A)Upstream Busbar Current (R) (A)Upstream Busbar Current (Y) (A)Upstream Busbar Current (B) (A)Upstream Busbar Current (N) (A)

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BS7671 Maximum Disconnection Time (s)Calculated Device Rating (A)Downstream Device Rating (A)Design value of IB (A)Design value of In (A)Device TypeDownstream Device TypeSockets in Circuit?Route Length Fixed by User?Cable has Grouping Limit?Symbol for Non-Localised Star-Delta Starting

Data Type 3 – Connected Loads Input Data (Use Anywhere In Schedules)

Circuit Number *Load TypeNumber of OccurrencesLoad ReferenceLoad Phase

Data Type 5 - Equipment Input Data (Use In Parts 3 & 4 Of Schedules)

Equipment Number *Circuit Number *Number of WaysDesign Level *Distribution Equipment TypeProvisional Loading (kVA)Provisional Power FactorProvisional Downstream Device Rating (A)Diversity (R) (%)Diversity (Y) (%)Diversity (B) (%)Spare Capacity (R) (kVA)Spare Capacity (Y) (kVA)Spare Capacity (B) (kVA)Spare Capacity Power Factor (R)Spare Capacity Power Factor (Y)Spare Capacity Power Factor (B)Third Harmonic (R) (%)Third Harmonic (Y) (%)Third Harmonic (B) (%)Busbar Live Resistance (mohm/m)Busbar Live Reactance (mohm/m)Busbar Neutral Resistance (mohm/m)Busbar Neutral Reactance (mohm/m)Busbar Earth Resistance (mohm/m)Busbar Earth Reactance (mohm/m)Equipment ReferenceEquipment DescriptionProvisional Downstream Device TypeEquipment Phase Code

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Data Type 8 – Special Combinations Of Data (Use Where Appropriate)

CPC TypeCPC Size (mm or sq.mm)CPC Length (Fixed or Maximum) (m)Load or Equipment Reference & DescriptionRoute Length (Fixed or Maximum) (m)Effective Length for Voltage Drop (Fixed or Maximum) (m)Design Current (R) (A)Design Current (Y) (A)Design Current (B) (A)Tabulated Cable Voltage Drop (mV/Am)Corrected Cable Current-Carrying Capacity (A)Spare Capacity (R) (A)Spare Capacity (Y) (A)Spare Capacity (B) (A)Connected Load (kVA)Cable DescriptionCPC Cable Description(1 space - use this as a spacer)(2 spaces - use this as a spacer)(4 spaces - use this as a spacer)

9.2.4.2. Standard Formats

The formats that have already been prepared for customised output are held in thestandard data file cforms1.dat. See Customised Schedules for details of how to make useof this data. The file may be viewed using a text editor such as Notepad.

Note that some of the formats (all formats whose titles begin with “Example”) are notintended for serious output but merely so that you can examine the effect of using eachitem before producing your own customised schedule formats.

field user guide

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