s-aa-swg-lv-ac-board (rev.0-2008)

STANDARD TECHNICAL SPECIFICATIONS FOR ELECTRIC WORKS

LV SWITCHGEAR

( SPECIFICATION )

STATION LV AC DISTRIBUTION BOARDS

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LV SWITCHGEARStation LV AC Distribution Boards

ADDC/AADC STANDARD : DOCUMENT.DOC

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CONTENTS

1 GENERAL....................................................................................................51.1 Drawings.....................................................................................................................61.2 Equipment Identification and Color Codes................................................................6

2 TECHNICAL DESCRIPTION...................................................................72.1 General........................................................................................................................72.2 Power Source..............................................................................................................72.3 AC Distribution Design Details..................................................................................72.4 Main AC Distribution Board......................................................................................72.4.1 General Requirements........................................................................................................72.4.2 Busbars and Insulators........................................................................................................92.4.3 Earthing Bus.....................................................................................................................102.4.4 Air Break Circuit Breaker (if applicable).........................................................................112.4.5 OFF-LOAD Isolator (if applicable)..................................................................................132.4.6 Moulded Case Circuit Breaker (MCCB) (if applicable)...................................................142.4.7 Relays...............................................................................................................................142.4.8 Voltage and Current Transformers...................................................................................142.4.9 Indicating Instruments......................................................................................................152.4.10 Control & Selector Switches............................................................................................152.4.11 Indicating Lamps..............................................................................................................152.4.12 Fuses.................................................................................................................................162.4.13 Control and Secondary Wiring and Terminal Blocks.......................................................162.4.14 AC Cable Termination......................................................................................................162.4.15 Description of Modules....................................................................................................162.4.16 Interlocking.......................................................................................................................192.4.17 Automatic Switching-Over...............................................................................................192.4.18 SCMS Requirements........................................................................................................202.4.19 Corrosion Protection/Painting..........................................................................................212.5 Sub-Main Distribution & HVAC Boards.................................................................212.5.1 General Requirements......................................................................................................212.5.2 MCCBs:............................................................................................................................212.5.3 Bus Bars............................................................................................................................222.6 Final MCB Distribution Boards...............................................................................222.6.1 General Requirements......................................................................................................222.6.2 M C B ‘S :.........................................................................................................................222.6.3 Residual Current Circuit Breakers....................................................................................222.7 Station Transformer..................................................................................................232.7.1 Heater................................................................................................................................232.7.2 Nameplates, Labels and Markings....................................................................................23

3 TESTING AND INSPECTION.................................................................243.1 General......................................................................................................................24

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3.2 Factory Tests.............................................................................................................243.2.1 Type Tests.........................................................................................................................243.2.2 Routine Tests....................................................................................................................253.3 Site Tests...................................................................................................................263.3.1 General Checks.................................................................................................................263.3.2 Operational Checks...........................................................................................................263.3.3 Measurements...................................................................................................................27

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STATION LV AC DISTRIBUTION BOARDS

1 GENERAL

This specification covers the design, manufacture, factory testing, marking, packing, shipping, transportation to site, installation, site testing and commissioning of the Station LV AC supply board.

Further detailed and specific data are contained in the drawings, Technical Data Sheets and other documents that form part of these Specifications.

The main LV AC distribution panel board shall be of 600 V/1000 V insulation grade and shall be designed and constructed to comply with the requirements of I.E.C.439-1 (BSEN 60439). The board shall be of Form (4) –TYPE 6 ( Bus Bars shall be separated from compartments). The boards shall be of modular cubicle pattern, floor mounted, front access, air insulated, totally enclosed, fully interlocked. The boards shall be of sealed version and vermin, corrosion, dust and damp proof to comply with degree of protection IP 54 as defined I.E. 529.

The housing should be constructed so that they will be suitable for future extensions at either end and will allow for interchangeability of switchgear. Provision shall be made for top, or bottom entries for cables as appropriate. All necessary cable boxes, glands and clamps appropriate to the cable sizes shall be provided.

The board shall be of suitable design to facilitate ease of cabling, maintenance, inspection and testing, and shall ensure maximum safety to operators, and to maintenance and testing Engineers.

Each panel door shall be fitted with approved type of lock.

The general arrangement of the board shall be indicated on the appropriate drawings. However, it shall be the responsibility of the Contractor to submit with his working drawings, for Engineer’s study and approval, the proposed arrangement and physical layout of the boards together with the manufacturer’s specifications and full technical details of the switch gear and all ancillary equipment the proposes to use.

The Contractor shall ensure that his offer shall include all items, whether or not explicitly specified, but which are considered necessary for a complete, safe and satisfactory installation. The Contractor shall also ensure that the boards offered shall be of suitable layout and dimensions for the locations specified. A complete set of plans indicating details and fixing dimensions together with the necessary number of foundation blots for each board shall be submitted.

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If necessary, the board shall be arranged for delivery to site in section which can be easily placed into positions and then bolted together. Lifting lugs shall be provided for each section. However the board is to be shipped from factory with assembled busbar system, apparatus group and metering system.

The board shall be installed complete in all respects and shall be tested and commissioned to the satisfaction and approval of the Engineer.

The MDB shall be type tested in accordance with BSEN 60439 –1 copy of test certificate from independent laboratory confirms that all type test mentioned under BSEN 60439-1 are passed , shall be submitted .

The Station LV AC supply board, to be offered, shall be complete in all respects for the effective and trouble free operation when connected to the system.

The Contractor shall submit test certificates such as ASTA/KEMA or as issued by any other independent testing authority confirming the declared short circuit ratings of Switch Boards and circuit breakers.

The Contractor is responsible for complying with all codes, which apply to the equipment. Any special certification requirements or inspection by other authorities arising from the above shall be arranged by the contractor and the costs for the same included in this quotation.

For applicable technical standards, tests and general requirements, reference shall be made to Standard Technical Specification, Part:

S-AA-SWG-MV-LV-GEN - General Requirements (Applicable Technical Standards, Tests, etc.)

1.1 Drawings

Typical Drawing for the LV Distribution Boards (inside buildings – Type 1 & outside buildings – Type 2) provided in the Drawings Section are as follows:

Drawing No. Title

ADWEA SWG 01 01 Conceptual Design of LV AC Station Supply Board (400V 3-phase & 230V single phase)

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1.2 Equipment Identification and Color Codes

Concerning LV AC Supply board identification, reference shall be made to Standard Technical Specification, Part:

S-AA-GEN-ID - Components Marking

2 TECHNICAL DESCRIPTION

2.1 General

The function of the AC Station Supply Board is to feed the auxiliary equipment as well as the lighting and other services via the relevant AC boards.

The LV AC system shall provide the following voltages:

400V, 50 Hz, 3-phase, 50 Hz, for power supply to auxiliaries

230V, 50 Hz, single phase, 50 Hz, for lighting, outlets, etc.

2.2 Power Source

The AC power supply shall comprise the redundant Station Service Transformers as a main source and the Standby Diesel Generator Unit (DGU) (if applicable) as a back up.

In the normal operation conditions the AC power is normally supplied from the main source i.e. from the station transformers, whereas in case the main supply is out of service, the emergency standby Diesel generator (if applicable) shall supply the entire load.

2.3 AC Distribution Design Details

The LV AC system shall consist of a star connected, solidly grounded four-wire system as well as a star-connected system for lighting, AC sockets and other essential AC loads.

The Station transformer or/and emergency generator shall each be sized to supply the substation with the required AC loads taking into considerations the present and future services at the substation final stage.

The station AC distribution boards shall be equipped with all equipment for the future final stage of the concerned station.

For Main AC Distribution Boards, Sub-Main Distribution Boards and Final MCB Distribution Boards Circuit Breakers a circuit breaker discrepancy study shall be carried out and submitted to AADC/AADC for approval.

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All circuit breakers of Main AC Distribution Boards, Sub-Main Distribution Boards and Final MCB Distribution Boards shall be made by the same manufacturer to simplify the discrepancy study.

2.4 Main AC Distribution Board

2.4.1 General Requirements

The AC distribution board shall be supplied complete with all instruments, meters, indicators, control switches or push-buttons, annunciators, indicating lamps, terminal blocks, wiring, circuit breakers & miniature circuit breakers and miscellaneous devices, etc.

The AC distribution boards, shall be of metal-enclosed, indoor floor-mounted, free-standing type and shall meet requirements as specified in Standard Technical Specification, Part:

S-AA-CUB - Cubicles & Enclosures

The frames of AC distribution board shall be fabricated using suitable mild steel structural sections or pressed and shaped cold-rolled galvanised sheet steel. Frames shall be enclosed in cold-rolled steel U-channels. Doors and covers shall also be of cold rolled sheet steel as well.

AC distribution board edges and cover/door edges shall be reinforced against distortion by rolling bending or by the addition of welded reinforcement member.

The complete structures shall be rigid, self-supporting, and free from flaws, twists and bends.

The AC distribution boards shall be of dust & vermin proof construction.

All cut outs shall be true in shape without sharp edges and shall be provided with neoprene/synthetic rubber gasket.

Distribution boards shall be supplied with base frame made of structural steel sections. Bidder/Contractor shall provide all necessary mounting hardware required for welding the base frames to the insert plates. Distribution boards shall be easily extendable from front and rear sides after installation at final location.

The AC distribution boards shall be divided into distinct vertical sections, each comprising of:

a) A completely enclosed bus bar compartment for running horizontal and vertical bus bars.

b) Completely enclosed switchgear compartment (s) one for each circuit for housing the circuit breaker.

c) A compartment for power and control cables.

d) A compartment for relays and other control devices associated with a circuit breaker.

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Sheet steel barriers shall be provided between two adjacent vertical panels running to the full height of the distribution board, except for the horizontal bus bar compartment. The front of the compartment shall be provided with the hinged single leaf door, with locking facilities.

After isolation of power and control circuits connections it shall be possible to safely carryout maintenance in a compartment with the bus bar and adjacent live circuit.

Wherever it is not possible to maintain the required clearance, sleeves or barriers shall be used to provide sufficient insulation. However for horizontal run of bus bar minimum clearance as specified in Technical Data Sheets should be maintained even if they are sleeved.

The temperature rise of horizontal & vertical bus bars when carrying 90% of the rated current along its full run shall in no case exceed 50oC with silver plated joints and 40oC with all other type of joints taking into consideration that the outside ambient temperature is 50oC.

All identical circuit breakers and strip fuse ways of same size shall be fully interchangeable without having to carryout modification.

Wherever, two breaker compartments are provided in the same vertical section, insulating barriers and shrouds shall be provided in the rear cable compartment to avoid accidental touch with the live parts of one circuit when working on the other circuit.

All modules shall be fixed type except air circuit breaker module.

All board components shall be neatly arranged and shall be easily accessible for operation and maintenance. The internal layout of all modules shall be subject to ADDC/AADC’s approval.

Adapter panels and dummy panels required to meet the various bus bar arrangements and layouts required shall be included in Bidder/Contractors scope of work.

2.4.2 Busbars and Insulators

The AC distribution board shall be provided with 3- phase and neutral busbars.

All bus bars and jumper connections shall be of high conductivity high purity tinned copper. The bus bars to be sized to carry the rated current of the switchgear without exceeding the temperature limit stipulated in IEC 439-2 and as specified in technical data sheets. They shall be air insulated.

The bus bar system to be made of horizontal and vertical bus bars and earth bar.

The bus bars to be located and sealed in a separate compartments. The busbar system is to be arranged in the most favorable form taking into consideration the dynamic forces due to short circuit and requirement of ventilation.

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The earth bar of size 30x10mm shall be provided running the whole length of the board and it should be electrically and mechanically connected to the frame by clamps.

The cross section of the busbars shall be according to the latest IEC 60865-1 recommendation, uniform throughout the length of switchgear and shall be adequately supported and braced to withstand the stresses due to the specified short circuit currents.

The neutral bus bar shall be of the same size as the phase busbar.

All bus bars shall be adequately supported by non-combustible, track-resistant & high strength type polyester fibre glass moulded insulators. Separate supports shall be provided for each phase and neutral busbar.

All joints of busbars shall be provided with high tensile steel bolts, spring washers and nuts, so as to ensure good contacts at the joints. Non-silver plated busbars joints shall be thoroughly cleaned at the joint locations and suitable contact grease shall be applied just before making a joint.

The Bidder/Contractor shall furnish calculations along with the bid, establishing the adequacy of busbar sizes for the specified current ratings.

Auxiliary buses shall be provided for control. The material for all auxiliary buses for control power supplies shall be of high conductivity high purity tinned copper.

The supply for AC auxiliary buses shall be tapped from the main power buses before the in-comer, for each switchboard.

2.4.3 Earthing Bus

The earthing bus shall be provided at the bottom of each panel and shall extend throughout the length of each distribution board. It shall be welded/bolted to the frame work of each panel and breaker earthing contact point vertical earth bus shall be provided in each vertical section, which shall in turn be bolted/welded to main horizontal ground bus.

The cross-section of the earthing bus shall be according to latest IEC 60865-1 recommendation and shall have sufficient cross-section to carry the momentary short circuit and short time fault currents to earth without exceeding the allowable temperature rise.

Suitable arrangements shall be provided at each end of the horizontal earth bus for bolting to Substation earthing conductors. The horizontal earth bus shall project outside the distribution

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board ends and shall have predrilled holes for this connection. All joints to earth bus shall be made through at least two bolts.

All non-current carrying metal work of the distribution board shall be effectively bonded to the earth bus. Electrical conductivity of the entire enclosure framework and the truck shall be maintained even after painting.

The truck and air circuit breaker frame shall get earthed while the truck is being inserted in the panel and positive earthing of the truck and breaker frame shall be maintained in all positions i.e., ‘SERVICE’ & ‘ISOLATED’, as well as through out the intermediate travel.

Each module frame shall get engaged to the vertical earth bus. Before the disconnecting contacts on the module are engaged to the vertical busbar.

All metallic cases of relays, instruments and other panel mounted board shall be connected to earth bus by independent standard copper wires of size not less than 2.5 mm2. Insulation color code of earthing wires shall be green/yellow. Earthing wires shall be connected to terminals with suitable clamp connectors and soldering is not acceptable. Looping of earth connection, which would results in loss of earth connection to other devices when a device is removed, is not acceptable. However, looping of earth connections between board to provide alternative paths or earth bus is acceptable.

VT and CT secondary neutral point earthing shall be at one place only, on the terminal block. Such earthing shall be made through links so that earthing of one secondary circuit shall be removed without disturbing the earthing of other circuits.

All hinged doors shall be earthed through flexible earthing braid.

Caution nameplate ‘caution-live Terminals’ shall be provided at all points where the terminals are likely to remain live and isolation is possible only at remote end.

2.4.4 Air Break Circuit Breaker (if applicable)

The circuit breaker shall be four poles, horizontal draw out type and shall have inherent fault current breaking and making capacity as specified.

Circuit breakers shall be mounted along with its operating mechanism on telescopic rails. The cradle should be so designed and constructed as to permit the smooth withdrawal and insertion of the breaker into it. The movement should be free of jerks and shall preferably be on rollers and not on the flat surface. Suitable guides shall be provided to minimize misalignment of the breaker.

There shall be preferable ‘Isolated’ and ‘Maintenance’ positions for the breakers.

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Main poles of the circuit breakers shall operate simultaneously in such a way that the maximum difference between the instants of contacts touching during closing shall not exceed half cycle of rated frequency.

The main contacts should be of appropriate Silver alloys. Only Silver plating of the faces shall not be acceptable.

Arcing contacts should be of tungsten base alloy and mere Silver plating of the faces shall not be acceptable. Arcing contacts must be separate from main contacts and one piece butt type contacts shall not be acceptable.

ACB assembly shall be capable of being easily removed for routine inspection of the chutes and contacts.

The moving portion of each circuit breaker shall consist of a three-pole circuit breaker with operating mechanism, primary and secondary disconnecting devices,

Auxiliary switches, position indicators and necessary controls wiring, all mounted on a substantial steel framework, This framework and all metal pars of the moving portion apart from current carrying parts shall, when inserting the circuit breaker into the cubicle, be solidly earthed before the circuit breaker reaches test position, the circuit breaker shall then remain effectively earthed when it is in the cubicle.

All feeders with more than 800 A should have withdrawable ACB type circuit breakers with manually and electrically operated spring charge mechanism.

The A.C.B to have 3 distinct positions.

Fully inserted position. Test position. Isolated position.

The trip functions to be solid state electronic type and consists of following with LED indication of type of trip.

Setting of base current Adjustable overcurrent protection with adjustable time delay Adjustable overload protection with adjustable time delay Adjustable instantaneous trip Adjustable ground fault trip

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Test functions to be provided as a standard on the breaker. The ACB should have following flag indicator.

On/Off indicator Spring charged/uncharged. Position indicator for connected, test, isolated position.

The ACB should have padlock for locking in the service, test or isolated position. Also the ACB to be lockable in off position.

The busbar to be covered by automatic shutters when the ACB is in withdrawn position.

All mechanical interlocks shall be of preventative type and shall be arranged to prevent malfunction as close as possible to the point at which mechanical force is applied, in order to prevent defeat of the interlocks by distortion of linkages. Electrical interlocks shall also function so as to prevent the closing of the circuit breaker before the interlocking demands are fulfilled.

Mechanical interlocks shall be provided which are designed to prevent:

A closed circuit breaker from being withdrawn or inserted into isolating the contacts. Tripping by attempted isolation. The closing of a circuit breaker except when correctl located in service or test position.

Circuit breakers of the same current and voltage rating shall be fully interchangeable, both electrically and mechanically. It must be impossible to insert a circuit breaker with lower data into a cubicle with higher data.

The ACB to be complete with the following:

a) Charging lever for the closing spring. b) Pushbutton for elimination of charging levelc) Indicator for closing springd) On buttone) Off button f) On/Off buttong) Position stopped release for withdrawable breaker. h) Hole for draw-out handlei) Padlock loop for locking of breaker in CONNECTED, TEST RO ISOLATED position. j) Position indicator for Connected, Test or Isolated position.

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k) The On and Off buttons are to be place behind sliding covers which serve to prevent unintentional actuation.

l) The ACB to be provided with automatic screening which can be padlocked. The screens for incoming and outgoing main terminals can be opened independently of each other.

Breaker controlling motors shall operate satisfactorily under the following conditions:

i. Direct on-line starting of induction motors rated 100 KW to 200 KW with a locked rotor current of seven times the rated current, and starting time of up to 30 seconds

ii. Breaking non-load, full load and locked rotor currents of induction motors rated for 100KW to 200KW.

Operated Mechanism

i) Circuit breakers shall be provided with motor operated spring charged mechanism. The motor shall be a universal motor suitable for operating from 110V DC with voltage variation from 85% to 110%.

ii) The charging time for closing springs shall not be more than 15 seconds.

iii) After failure of power supply at least one open-close –open operation shall be possible.

iv) Provision shall be made for emergency manual charging of closing spring.

v) Circuit breakers shall be provided with closing and tripping coils. The closing coil shall operate correctly for voltage variation between 85% to 110% and trip coil for voltage variation between 70% to 110%.

vi) Mechanical tripping/closing shall be possible by means of front mounted red/green colored trip push button. These push buttons shall be shrouded to prevent accidental operation.

vii) Circuit breakers shall be provided with mechanical indicating devices to show OPEN, CLOSE and SPRING CHARGED conditions.

Circuit breaker shall be provided with under voltage release wherever specified.

Provision shall be made to lock the breaker in “Isolated” position.

It shall not be possible to open the board door when the circuit breaker is in ‘CLOSED’ position. Built-in interlock should be provided to prevent closing the breaker being inserted into panel.

2.4.5 OFF-LOAD Isolator (if applicable)

The OFF-LOAD Isolator shall be, horizontal draw out type and shall have inherent fault current breaking and making capacity as specified.

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2.4.6 Moulded Case Circuit Breaker (MCCB) (if applicable)

All MCCB’s protecting outgoing feeder circuits shall be of instantaneous type and shall be designed and constructed to have short circuit breaking capacity of not less than 50 KA, and shall conform to the requirements, including latest amendments, of IEC 947-2 (BSEN 60947-2) 1992, and shall be fault tested to category P2 (ICS) of these standards.

All MCCB’s shall be of thermal magnetic, manually and automatically operated type and shall be designed to provide positive trip-free operation on abnormal overloads with quick break contacts for both manual and automatic operation. Adequated protection for the stationary and movable contacts shall be provided with effective and rapid arc interrupting devices. An inverse time delay thermal overcurrent trip element and a magnetic instantaneous overcurrent trip element shall be provided on each pole of the breaker for common tripping of all poles.

2.4.7 Relays

All relays and timers in protective circuits shall be flush mounted on panel front with connections from the inside. They shall have transparent dust tight covers removable from the front. All protective relays shall have a draw out construction for easy replacement from the front. They shall also have built-in test facilities and shall be provided with necessary test blocks and test switches located immediately below each relay. The auxiliary relays and timers may be furnished in non- draw out cases.

All AC relays shall be suitable for operation, at 50 Hz with 110V VT secondary and 1 amp, CT secondary.

DC auxiliary relays shall be designed for 110V DC unless otherwise specified and shall operate satisfactorily between 70% and 110% of the rated voltage. Relays shall have adequate thermal capacity for continuous operation in circuits in which they are used.

All protective relays and timers shall have at least two potentially free output contacts. Relays shall have contacts as required for protection schemes. Contacts of relays and timers shall be Silver faced and shall have a spring action. Adequate number of terminals shall be available on the relay cases for applicable relaying schemes.

All protective relays, auxiliary relays and timers shall be provided with hand reset operation indicators (flag) for analysing the cause of operation.

DC supply for Protection relays shall be controlled with separate MCB and monitoring at SCMS.

2.4.8 Voltage and Current Transformers

For voltage and current transformer requirements, reference shall be made to Standard Technical Specification, Part:

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S-AA-SWG-LV-VTCT - Voltage and Current Transformers

2.4.9 Indicating Instruments

For indicating instrument requirements, reference shall be made to Standard Technical Specification, Part:


Ammeters provided on motor feeders shall have a compressed scale at the upper current region to cover the starting current.

Watt-hour meters shall be of 3-phase, 3-element type, maximum demand indicators shall be provided.

2.4.10 Control & Selector Switches

For control & selector switches requirements, reference shall be made to Standard Technical Specification, Part:


For push buttons requirements, reference shall be made to Standard Technical Specification, Part:


All pushbuttons shall have one normally open and one normally closed contact, unless specified otherwise.

All push buttons shall be provided with integral escutcheon plates marked with its function.

2.4.11 Indicating Lamps

For indicating lamps requirements, reference shall be made to Standard Technical Specification, Part:


Indicating lamps shall be of the panel mounting filament type and low watt consumption. Lamps shall be provided with series resistors, preferably built-in the lamps assembly. The lamps shall have escutcheon plates marked with its function, wherever necessary.

For Indicating Lamps Color Specification, reference shall be made to Standard Technical Specification, Part:

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S-AA-GEN-ID - Components Marking

When associated with push buttons, red lamps shall be directly above the green push button, and green lamps shall be directly above the red push-button.

2.4.12 Fuses

For fuses requirements, reference shall be made to Standard Technical Specification, Part:


2.4.13 Control and Secondary Wiring and Terminal Blocks

AC distribution boards shall be supplied completely such that it is wired internally up-to the terminal blocks, ready to receive control cables at site.

For control and secondary wiring and terminal blocks requirements, reference shall be made to Standard Technical Specification, Part:


2.4.14 AC Cable Termination

Cable termination compartment shall be suitable for stranded copper conductor, XLPE insulated and armoured single core/four cores, of voltage grade of 1100V.

All necessary cable terminating accessories such as gland plates, supporting clamps and brackets, power cable lugs, hardware etc. shall be provided by the Bidder/Contractor, to suit the final cable sizes.

All the cable terminating accessories and materials shall be of non-magnetic type.

The gland plate shall be of removable type and shall cover the entire cable alley.

Bidder/Contractor shall also ensure that sufficient space is provided for all cable glands.

For all single core cables, gland plates shall be of non-magnetic material.

2.4.15 Description of Modules

Each AC distribution board shall comprise of a number of different types of modules as shown below:

The bill of material for each type of module and the number of modules is for Bid purpose and any modifications in respect of the following shall be amended as required during the design/engineering stage.

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a) Addition /deletion/change of electrical hardware within module.

b) Changes in the number and types of modules in a board.

For incoming and bus coupler circuits:

a) One four poles air circuit breaker with motor operated mechanism.

b) Neutral link.

c) Circuit breaker control switch.

d) Current transformers for metering.

e) Three Ammeter.

f) Current transformers for protection.

g) Built-in microprocessor-based, 3-element over-current with IDMT characteristics and single element adjustable definite time sensitive earth-fault relay. The protection curves and all other settings shall be adjustable through rotary switches when viewed at the front, clearly showing the unit settings. The protection setting range and minimum pick-up current shall be in accordance with the protection of motors of ratings 100 kW to 200 kW.

h) HRC control fuses auxiliary contactors.

i) Indicating lamps as required.

For Motor Feeder:

a) One triple pole air circuit breaker with motor operated mechanism and control switch.

b) Current transformers for metering.

c) Three Ammeter.

d) Current transformers for relaying.

e) One triple pole IDMT instantaneous over current relay. The relay setting range shall be continuously adjustable between 200-800% or 400-1600% of CT secondary rated current and time setting range of 0-30 seconds.

f) Microprocessor-based, 3-element over-current with IDMT characteristics and single element adjustable definite time sensitive earth-fault relay housed within the pilot box accessible from the front. The protection curves and all other settings shall be adjustable through rotary switches when viewed at the front, clearly showing the unit settings. The protection setting range and minimum pick-up current shall be in accordance with the protection of motors of ratings 100 kW to 200 kW.

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g) The relay shall have adjustable setting range of 50% to 200% of CT secondary current and time setting range 0-30 seconds.

h) It should be possible for the relay to perform a self-check giving clear indication of the status of the over-current and earth-fault elements.

i) One instantaneous earth fault relay having an adjustable setting range of 10-40% of CT secondary current. The earth fault relay shall be provided with a stabilising resistor.

j) Indicating lamps as required.

k) HRC control fuses auxiliary contactors.

For incomer from Diesel Generator Set (if applicable):

a) One triple pole air circuit breaker with operated mechanism and control switch.

b) Current transformers for metering.

c) Current transformers for relaying.

d) Three ammeter.

e) One wattmeter of the range 0-600 kW, two element type.

f) One watt-hour meter with six digits and minimum count of 1 kW.

g) One three pole voltage controlled definite time delay relay having current setting range of 50-200% of CT secondary current and adjustable time delay of 0.3 to 3 seconds.

h) Single pole definite time over current relay having a continuous setting range of 50-200% of CT secondary current and a time delay of 2.5-25 s connected in Y phase only for overload alarm. The relay shall have a setting on not less than 90%.

i) Indicating lamps as required.

j) HRC control fuses.

k) Provision shall also be kept for three current transformers for differential protection and one three pole differential protection relay for diesel generator, characteristics of these items shall be intimated to the successful Bidder/Contractor.

l) Frequency meter, voltmeter with selector switch, Remote local selector switch.

m) Automatic synchronising relay.

For outgoing feeders:

a) Moulded Case Circuit Breaker (MCCB).

For VT with under voltage relay and voltmeter:

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a) Three 230/110 volts single phase voltage transformer star/star connected with star point solid earthed of an accuracy class of not less than 1.0 and rated burden or 10 VA for metering and class 3p for protection with 50 VA burden shall be provided. VTs shall be mounted on common draw out chassis.

b) One four-position voltmeter selector switch.

c) One voltmeter (0-300V).

d) One double pole under voltage relay with timer. The setting range of relay shall be 40% to 80% of rated voltage and timer shall have a range from 1 sec to 5 sec. In steps of 0.5 sec. The relay shall have separate contacts for alarm and tripping.

e) One time delay pick up relay having a time setting range of 0.5 to 3 seconds and 3 ‘NO’ self reset contacts, suitable for 110V DC.

f) One auxiliary relay 110V DC with 4 ‘NO’ self reset contacts.

g) HRC control fuses.

h) Three indicating lamps with series resistor and color lenses (red, blue, and yellow).

For Voltmeter:

a) Voltmeter (0-300V).

b) One four-position voltmeter selector switch.

c) HRC control fuses, indicating lamps.

For Annunciation:

Annunciation system shall have sufficient number of alarm windows. The alarm fascia shall have translucent plastic window of 3x50mm (minimum) size engraved with appropriate function in black letters for each alarm point shall be provided on the module.

Annunciator shall be suitable for operation on 110V DC and shall have a single alarm buzzer common to all points. Three pushbuttons for audible alarm acknowledge, trouble lamp reset and lamp test with appropriate nameplates shall be provided common to all alarm points.

Annunciator shall be suitable for operation with both normally NC and NO alarm contacts. Annunciation system shall be solid type of reputed make. On receiving an alarm impulse, even if momentary, the appropriate alarm relay shall get energised and correspondingly a visible and audible alarm units. It shall be possible for the operator to reset the audible alarm even if the alarm (fault) condition persists. However visible alarm shall not reset unless the alarm condition has disappeared and the operator then presses the lamp reset push button.

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Annunciator shall have sealed in lamp indication and audible alarm shall be ready to operate by any new alarm condition immediately after the alarm is reset for previous alarm condition. Annunciator shall operate satisfactorily between 80% and 110% of rated supply voltage.

2.4.16 Interlocking

The incoming feeder circuit breakers from station transformers and bus coupler breaker should be so interlocked that paralleling of both the incoming supplies is prevented.

In-comer breaker from diesel generator should not close if any of the incoming AC supply to AC board is healthy.

2.4.17 Automatic Switching-Over

If there are two or more incoming feeders connected to the main board, they shall be connected to an automatic changeover device with circuit breakers.

Simultaneous feeding from more than one source is not permitted. The automatic changeover power and control device shall be fed from the D.C. system.

The automatic device shall make sure that a voltage supply is always available.

In the case of losing one of the two AC supply voltages, the automatic device will changeover to another supply.

The changeover shall be indicated on the alarm panel.

There must be a time delay in the changeover operation between the two supplies.

Connections between the two supply systems shall be prevented by an interlocking system.

The secondary circuit breakers of the two main power supplies feeding the main 400V switchboard shall have selector switch with two positions:

Position 1 : off duty

Position 2 : automatic.

Any tripping, either from sub-distribution protection or manually, shall block the automatic changeover system. The blocking shall be indicated visually.

Automatic and manual interlocking scheme shall be provided between the two main circuit breakers in order to prevent their parallel operation.

2.4.17.1 Voltage Measuring

A 3-phase voltage relay, which measures each phase independently, shall be furnished. The voltage level has to be 80-85% of the rated voltage in order to prevent a false indication caused

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by remaining voltage at lost phase. Provisions shall be made such that actuation of the voltage relay will automatically transfer all the bus loads with faulty power source to the other power source.

In case of voltage dip below 70% of the rated voltage, the motors in operation on distribution board connected on a faulty power source shall be switched-off automatically. On resuming the voltage, within a pre-set time, which can be variable between 0.5 to 3 sec and upon the changeover device activation or restoration of normal power supply, the motor starters (contactors) shall switch-on automatically again in pre-selected time steps so that the starting current drawn by the starting motors does not cause a voltage drop of more than 20% on the motor terminals.

There shall be a time delay (1-10 sec) of voltage indication to prevent the changeover device from working at auto-reclose.

If measuring relays are placed in a control board, they must be connected via voltage transformers.

Measuring points are:

Before breaker on secondary side of transformer

On busbars.

2.4.18 SCMS Requirements

Contacts for the following SCMS inputs shall be provided:

a) Under-Voltage Relay: OPERATED

b) Annunciation Device: FAILED

c) O/C & EF relay operated

d) Inter trip from ADDC side

e) Changeover mode ( Auto / Manual )

f) Protection relay faulty

g) Trip circuit supervision fail

h) Main DC supply fail

i) DC MCB trip for incomers and bus section

j) AC MCB trip

k) Primary & Secondary VT MCB trip for incomers and bus section

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l) Outgoing MCB trip

m)LVAC Common alarm

2.4.19 Corrosion Protection/Painting

For Corrosion Protection measures, reference shall be made to Standard Technical Specification, Part:

S-AA-CORR - Corrosion Protection and Painting Color Codes

2.5 Sub-Main Distribution & HVAC Boards

The Contractors shall supply, install, test, connect and commission in the approximate locations indicated on the drawings, sub-main L.V. MCCB distribution panel boards, as specified in these specifications and as detailed in the L.V. distribution schematic drawings.


All SMPB’s shall be of 600V/1000V insulation grade and shall be capable of with standing short circuit fault levels of 35 KA per 1 Sec. These shall be of the wall mounted type and shall be totally enclosed, vermin, dust, damp and corrosion proof to approved finish, complying with BS 5486 IEC 439-1 and degree of protection IP 31, Provision shall be made for top or bottom entry for the outgoing cable and bottom entries for all incoming cables. The board shall be of Form (2).

Three ammeters and voltmeter with integral phase shift switch shall be required on each of these boards. The contractor shall furnish technical details of the proposed equipment to the ADDC/AADC for his approval.

All SMPB’s shall be installed complete in all respects and shall be tested and commissioned to the satisfaction of the ADDC/AADC.

All feeders with more than 800 A should have withdrawable ACB type circuit breakers with manually and electrically operated spring charge mechanism.

2.5.2 MCCBs:

MCCBs shall generally conform to the requirements, including latest amendments of IEC .

All MCCB’s shall be designed and constructed to have a short circuit breaking capacity of not less than 35 KA. They shall be of quick make, quick-break, trip free with silver fixed and moving contacts and arc chutes.

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An inverse time delay thermal over current trip element and a magnetic instantaneous over current trip element shall be provided on each pole of the breaker for common tripping of all poles.

2.5.3 Bus Bars

Bus bars of adequate current carrying capacity of highest conductivity tinned copper complying with BS 159 : 1957 shall be rigidly fixed on insulating supports to withstand short circuit mechanical and thermal stresses. Reduced section neutral bus bars shall not be allowed.

All bus bars and connections shall comply with the requirements of BS5486L:Part I : 1977. All joints shall be carefully prepared, cleaned and treated to prevent oxide formation.

2.6 Final MCB Distribution Boards

The Contractor shall supply, install, test and connect MCB distribution boards in each area or floor, the approximate locations indicated on the drawings .


All final/MCB Boards shall be equipped with incomer MCCB or RCCB 30/100 ma with current rating as indicated in the load schedules.

These boards shall be constructed of sheet steel enameled to light grey colour and shall be manufactured to comply with the requirements of BS 5486:1977, part 12. All boards shall be factory fabricated and shall be factory fabricated shall be totally enclosed, dust, vermin, damp and corrosion proof. (the boards shall be generally be of the flush or surface mounted type depending on location and purpose of use). With a cover, lock and key the boards shall be labeled as previously described and a neatly typed schedule, inside the board, shall describe all the outgoing final sub-circuit, their ratings and the areas and points served.

2.6.2 M C B ‘S :

All MCB’s shall be of high performance, rapid interrupting, current limiting type designed and type tested to BSEN 60898 (IEC 898), including latest amendments. These shall be of type B characteristic for all general lighting and small power circuits, and of type C characteristic for circuits supplying pumps, A/C units, street lighting etc. Category of duty shall be (10 KA).

2.6.3 Residual Current Circuit Breakers

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In addition to the overcurrent and short circuit protection afforded by MCB’s every circuit supplying, 13A socket outlets, water heater, water cooler, cooker unit,wet area & etc shall be equipped with a Residual current circuit Breaker (ELCB+MCB=RCBO) conforming to BS 4293 : 1983 to provide protection against shock and earth leakages. The sensitivity of these units shall be 30 mA.

2.7 Station Transformer

Electrical connections to the station transformer(s) shall be so designed such as these may be disconnected and re-connected at site to facilitate the removal of any major component of the AC distribution board.

The interconnection of the 0.4 kV air break circuit breaker and 0.4 kV bushings of the station transformers shall be made by using suitable Single Core XLPE cables with plug-in/conventional type connection of an acceptable make, which shall be dimensioned and mounted in such a way to withstands thermal and mechanical stresses arising from normal operation and under short circuit conditions.

For the technical details of station transformer(s), reference shall be made to Standard Specification, Part:

S-AA-TRAFO-ATR-O - Auxiliary / Distribution Transformers (Floor Mounted oil-insulated)

S-AA-TRAFO-ATR-D - Auxiliary / Distribution Transformers (epoxy-resin dry type, indoor installation)

2.7.1 Heater

LV AC Distribution boards shall be equipped with a space heater, fed from a separate power source. The space heater shall be protected by a two-pole MCB with auxiliary N/C contact wired to a group alarm terminal and shall be equipped with an integral thermostat for control. The heater shall be located at a suitable position and its capacity shall be as required to maintain the interval temperatures above the dew point taking into consideration the specified environmental conditions. A switch for each heater shall be provided so that the heater circuit can be switched “ON” or “OFF” as required independently. The heating elements shall be installed vertically, with minimum all round clearances of 50 mm.

For anticondensing heater requirements, reference shall be made to Standard Technical Specification, Part:


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2.7.2 Nameplates, Labels and Markings

AC distribution boards shall be provided with prominent, engraved identification plates. The module identification plate shall clearly give the feeder number and feeder designation. For single front switchboards, similar panel and board identification labels shall be provided at the rear also.

All nameplates shall be of non-rusting metal of 3-ply lamicoid with white engraved lettering on black background. Inscriptions and lettering sizes shall be subject to ADDC/AADC’s approval.

Suitable plastic sticker labels shall be provided for easy identification of all boards, located inside the panel/module. These labels shall be positioned in such a way to be easily & clearly visible and shall identify the device with the same number give in the module wiring drawings.

3 TESTING AND INSPECTION

3.1 General

All LV AC distribution board components shall be tested in the Manufacturer’s work. The Bidder/Contractor may be required to carry out any one or all of the tests stated in this Specification under witness of ADDC/AADC or his representatives.

Testing of the battery and all LV AC distributed board components shall be performed in line with this specification and in accordance with the relevant IEC Standards (as minimum requirement) and other Standards as may be approved by ADDC/AADC.

The LV AC distribution board shall be subject to inspection and test by ADDC/AADC’s engineers.

Acceptance by ADDC/AADC’s representative of any unit shall not relieve the manufacturer from any of his performance guarantees or from any other obligations.

Test certificates for each unit shall be submitted prior to delivery of the unit.

ADDC/AADC reserve the right to perform checks during manufacturing process at any time or all the times. It shall be at the discretion of ADDC/AADC to witness tests on 100%, or any percentage quantity of each lot for routine tests, apart from the type tests, wherever called for.

Testing of the LV AC distribution boards shall include the factory and site tests.

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3.2 Factory Tests

3.2.1 Type Tests

Evidence shall be given that the proposed LV AC distribution board components to be supplied under this Contract have been subject to all type tests at an internationally recognised testing station, like KEMA or equivalent. If deemed necessary, ADDC/AADC will decide whether additional tests are necessary to be performed by the Bidder/Contractor.

An internationally recognised laboratory shall certify the type test reports.

The Bidder/Contractor shall submit certified copies of type test certificates covering the proposed LV AC distribution board components.

Type tests certificates/reports shall be considered acceptable if they are in compliance with the relevant Standards and the following:

1. Type Tests conducted at an internationally recognised laboratory acceptable to ADDC/AADC.

2. Type Tests conducted at the manufacturer’s laboratory and witnessed by representatives from an internationally recognised laboratory acceptable to ADDC/AADC.

If the presented type test reports are not in accordance with the above requirements, ADDC/AADC may decide to ask for the type tests to be carried out in the manufacturer’s premises or other places subject to the approval of ADDC/AADC and at no additional cost. These tests shall be performed in the presence of an internationally recognised laboratory, which should issue the relevant type test certificates upon successful test.

3.2.2 Routine Tests

LV AC distribution boards, circuits breakers, instrument transformers, relays, meters etc., shall comply with the type test requirements and subjected to routine tests as per the relevant IEC recommendations.

Routine test certificates shall be submitted for ADDC/AADC’s review and approval before shipment of the LV AC distribution boards.

The following tests shall be performed as a minimum requirement:

a) Loop (Voltage Drop) Tests of all Wiring including meggering

A complete point to point test of all wiring against the latest wiring diagram shall be made to ensure that the assembly has been wired in accordance with its wiring diagram and further to ensure that the wiring diagram for any assembly is an accurate representation of that assembly.

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Each circuit or bus shall be subjected to an individual 1000V megger test with a minimum permissible reading of 6 megaohms.

b) Check of All Meters and Instruments

In order to ensure correctness of the connections between the associated incoming blocks and the instruments and meters, it is required that three-phases voltage and current be applied at the terminal blocks with the proper phase angle relationship to check the direction of rotation.

c) Complete Functional Test

This test is intended to completely check the functional operation of the board. The test shall be a check of all the tripping, closing, changeover switching, auxiliary circuits, interlocking, etc., for each panel or unit.

d) Interlocking Tests

e) Primary injection test for all circuit breakers and meters

f) Secondary test for all protection relays

g) Insulation test

Visual inspection of the entire board, in order to ensure that all components are mechanically assembled and fixed properly and that there are no imperfections shall be performed.

3.3 Site Tests

The following site tests, but not limited to, shall be carried out after installation and prior to putting in service:

3.3.1 General Checks

a) Check that the AC distribution panel is properly assembled.

b) Check for possible damages.

c) Check the AC panel for cleanliness including interior.

d) Check the frame earthings.

e) Check apparatus earthings.

f) Check earthing devices and earth terminals.

g) Check the gland plates.

h) Check the cable support.

i) Check the terminal arrangement.

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j) Check painting.

k) Check rating plates, manufacturer plate.

l) Check keys.

m) Check conductor cross-sections.

n) Check air gaps.

o) Check lifting rings

p) Check the cable arrangement

q) Check the internal components as per the approved drawing

3.3.2 Operational Checks

3.3.2.1 Mechanical Operating Tests

a) Circuit-breakers.

b) Isolators.

c) MCBs.

d) Switches.

e) Operating devices.

f) Door, coverplates and their locks

g) Torque test for bus bar joints

h) Phase sequence & loss of phase

3.3.2.2 Electrical Operating Tests

a) Phase sequence.

b) Main and auxiliary voltage.

c) Local control.

d) Remote control.

e) Interlockings.

f) Releases.

g) Operating change-over automation.

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3.3.3 Measurements

3.3.3.1 Voltage Test 2000 V, 50 Hz, 1 min (IEC 60255-4)

a) R+Y+B+N/ framework.

b) R/Y+B+N+ framework.

c) Y/R+B+N+ framework.

d) B/R+Y+N+ framework.

e) N/R+Y+B+ framework.

3.3.3.2 Insulation Resistance 500 VDC, R > 50 Mohm (IEC 60255-5)

a) R+Y+B+N/ framework.

b) R/Y+B+N+ framework.

c) Y/R+B+N+ framework.

d) B/R+Y+N+ framework.

e) N/R+Y+B+ framework.

f) Current Transformer testing

3.3.3.3 Voltage transformer testing

3.3.3.4 Protection relays testing

3.3.3.5 Ammeters, Voltammeter and Energy meter (KWH) calibration test.

3.3.3.6 Air Circuit breaker test

3.3.3.7 Current and Voltage transducer testing

3.3.3.8 Bus Bar contact resistance test.

3.3.3.9 AC high voltage test ( 2 KV AC / 1 min. ) for bus bar .

3.3.3.10 Tripping of CB through protection relay

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s-aa-swg-lv-ac-board (rev.0-2008)

Documents

ac distribution design

main ac distribution

ac cable termination

general requirements

air break circuit breaker

technical description

control selector switches

secondary wiring