ed1 and 2 electical drawings and appendix

Specialist Diploma in M&E Coordination Electrical Drawings

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1. Electrical drawings LEARNING OUTCOMES Upon completion of this lesson, you will be able to

Identify drawing symbols used in CAD drawings. know how many types of drawings are there generally know the good practices in single line diagram drawings identify simple mistakes in single line diagrams know the purpose and use of shop drawings

1.1 Introduction In the past when buildings were small, the developer or builder would just describe to the electrician what was required. They would agree on a price, the electrician would start work and receive ad hoc instructions. As projects grew in size, it became increasingly important to document the developers requirements using engineering drawings. The electrical drawings and specifications is a way of communicating the exact requirements of the developer, in both the quality and the quantity of the installation. It will then form the basis of the tender price and contractual obligations of the contractor. After construction, the electrical drawings are used as a record of the electrical installation and distribution. 1.2 Drawing symbols In early days, there were no real drawing standards regarding the standards used. There was heavy reliance on the legend key of each drawing for the interpretation of symbols. Symbols used could vary from designer to designer. Later when CAD drafting tools began to be used widely, there was a general standardization of symbols. CP83: Part II 2000 provides a list of symbols used commonly in CAD drawings. The symbols are as shown in Appendix A at the end of this chapter. You are required to be familiar with commonly used symbols.


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1.3 Types of drawings There are many types of drawings used by different parties in the electrical industry. Some of them are listed below

a) Single line diagrams. b) Layout plans for lighting and socket outlets c) Trunking layout d) Layout of under floor trunking e) Elevation showing riser ducts f) Site plan showing cable routes of incoming cables g) Shop drawings. h) As built or installation/layout drawings.

Single line diagrams are generally produced by designers and serve as a guide to the contractor for tendering and installation purposes. Single line diagrams use electrical symbols, connected with lines and annotated with text. Shop drawings are generally produced by specialist equipment makers (e.g. transformer or switchboard manufacturers) and are typically important for setting aside space during the construction stage of the project. Installation/layout drawings are produced by contractors as a guide for their workers to install. When the installation is completed, the contractors will update the drawings and submit them to the owner as a record. The installation drawings also serve as a record for claims by the contractor. This is especially so when there variation works on site.


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1.4 Single line diagrams Figure 1.4.1 shows a typical main single line diagram. The following good practices should be followed in the preparation of single line diagram drawings:

a) To indicate the salient technical details of the circuit control equipment and interlocks at the main switchboard, standby generator and etc.

b) To indicate against each main switchboard the contracted load in

kW. You should indicate the power factor assumed.

c) To indicate clearly the position(s) of revenue metering current

transformers or revenue metering points and the main/sub-mains circuits serving the landlords and tenants requirements where multiple customers are being served by the same supply lines.

d) To indicate clearly positions of all current transformers, CT

ratios, class of accuracy and VA burden for metering and protective relays. You should also specify the type of protection to be provided for the incoming and/or outgoing circuits.

e) To indicate against ALL incoming/outgoing circuit breakers on

the main intake switchboard, the number of poles, the rating and the short time withstand current ratings of the switchgear.

f) To indicate provision of pilot lamps before the incoming circuit

breakers/switch for monitoring of the status of the main incoming supply service.

g) To indicate the proposed metering scheme for the installation.


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WATER PUMPSSWITCHBOARDNDB 1 AIR-CON MSB

NDB 2

TDB 1-2

TDB 2-2

TDB 3-2

TDB 4-2TDB 4-1

TDB 3-1

TDB 2-1

TDB 1-1

EDB1

LIFT MOTORSWITCHBOARD

FIRE PUMPSSWITCHBOARD

300ATPN36kAMCCB

300ATPN36kAMCCB

60ATPN36kAMCCB

800ATPN36kAMCCB

800A TPN36kAMCCB

100A TPN36kAMCCB

200A TPN36kAMCCB

60ATPN36kAMCCB

100ATPN36kAMCCB

60ATPN36kAMCCB

kWh

A

V

OC E F 1000A

4P36kAACB

CL 5P10, 20VA1000A/5AProtection CT

2A0 - 400V

0 - 1000ACL1, 20VA1000A/5AMeasurementCT

1000A/5A(SP) 2A

R Y B

2A R Y B

Shunt Trip

V

R Y B

0 - 400V

0 - 1000A

1000A/5A(SP)kWh 2A

CL1, 20VA1000A/5AMeasurementCT2A

CL 5P10, 20VA1000A/5AProtection CT

1000A4P36kAACB

FEC

O

2AR Y B

Shunt Trip

1000A 4P36kA ACB

(coupler)

Mechanical & Electrical Interlock

INCOMING 1 INCOMING 2

CL 5P10, 20VA150A/5A

B

O

0 - 150A

2A

kWh2A

CL1, 20VA150A/5A\

150A/5ACL 0.5, 15VA

0 - 400V

R Y

V

Shunt Trip

C FE

2A R Y B

G

Roof Level

4th Floor

3rd Floor

2nd Floor

1st Floor

ControlPanel

150A TPN36kAMCCB

150A TPN36kAMCCB

EARTH ELECTRODE IN RING CIRCUIT.WITH 3mm X 25mm BARE COPPER TAPE

4 SETS OF 52mm X 12.5 mm COPPER BUSBARS

LV MAIN SWITCHBOARDEMERGENCYSWITCHBOARD

Approved Load : 1400 KVAMax DD:100KVA

100 KVAGenerator Set

CONSUMER'S LV DISTRIBUTION BOARD

REMARKS1. Indicator lights for incoming cables to indictate whether the incoming cable is "LIVE". Indicator lights for outgoing is to indicate whether the busbars are "LIVE"

2. Voltmeter with 7-position selector switch to read the live voltages & phase voltages.

3. Ammeter with 4-poistion selector switch to read the red, yellow & blue line current.

4. For MSB with rated current more that 300A, ,current transfomers must be provided to reduce power current to a smaller current for protective relays, ammeter and KWh meters.

5. Protection current transformers together with the protective circuit must be installed before all other instrumentation meters (i.e. voltmeter, ammeter, KWh meter)

6. Busbars current rating load density for copper busbar is 1.56A per sq. mm. (52 x 12.5 mm sq. x 1.56 = 1014A) 1000A rated current of the MSB.

LEGEND

kWh

V

YR B

CO

EF

G

4P 150AATS

Kilowatt Hour Meter

Current Transformer

Fuse

Selector Switch

Ammeter

Voltmeter

Indicating Lights

Overcurrent Protective relay

Earth Fault Relay

Automatic Transfer Switch

Generator

300A

BU

SD

UC

T

300A

BU

SD

UC

T

4 x1

C 9

5 sq

mm

cu

pvc/

pvc

+1

x 1C

50

sq m

m C

u pv

c cp

con

cab

le tr

ay

4 x1

C 2

5 sq

mm

cu

FR +

1 x

1C 1

6 sq

mm

Cu

cpc

on c

able

tray

1 x

1C 1

6 sq

mm

Cu

cpc

on c

able

tray

4 x1

C 3

5 sq

mm

cu

FR + 4 x1

C 1

6 sq

mm

cu

FR +

1 x

1C 1

6 sq

mm

Cu

cpc

on c

able

tray

4 x1

C 1

6 sq

mm

cu

pvc/

pvc

+1

x 1C

16

sq m

m C

u pv

c cp

c on

cab

le tr

ay

1 x

1C 9

5 sq

mm

Cu

pvc

cpc

on c

able

labb

er4

x1C

400

sqm

m c

u pv

c/pv

c +

1 x

1C 1

6 sq

mm

Cu

pvc

cpc

on c

able

tray

4 x1

C 3

5sqm

m c

u pv

c/pv

c +

1 x 3C 35 sq mm CU FR +16 sq mm cpc on Cable tray

Figure 5SLD for Consumer Taking LV at 1400kVA.

Figure 1.4.1 Single line diagram


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There about 10 mistakes and/or omissions in the single line diagram shown in figure 1.4.2 on the next page. List down the mistakes and omissions in the diagram

Figure 1.4.2


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1.5 Shop drawings Shop drawings are typically produced by equipment specialists and should show the following:

a) Dimensioned construction details of all manufactured equipment with schematic wiring diagrams (including small wiring diagrams).

b) Dimensions and locations of all recesses and openings (floor and wall)

to be done by others.

c) Indications of weights and reactions of all large equipments and locations of beams, plinths foundation and etc.

d) Indications of additional offsets required in trunking, ducting, conduits

etc to allow for installation in the actual available space. The important considerations in the preparation of shop drawings are as follows:

a) Accessibility (Front/back/side access). b) Clearance around equipment.

All shop drawings produced by equipment specialists should be vetted by designers prior to actual site construction and installation. Figures 1.5.1, 1.5.2, 1.5.3, 1.5.4 and 1.5.5 are typical shop drawings produced by transformer manufacturers. What are the important details shown in the five drawings? (Hint: Not all details are important)


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Figure 1.5.1 General dimensions

Figure 1.5.2 High voltage cable connection terminals

Figure 1.5.3 Low voltage bus duct connection

Figure 1.5.4 Transformer Plinth


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Figure 1.5.5 Rating plate


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In summary, we have seen the usefulness of two types of drawings single line drawings and shop drawings. Single line diagram is used to indicate important details such as cable sizes, circuit breaker ratings and equipment sizes. Shop drawings are typically useful in confirming the space and opening details required to accommodate that particular equipment. 1.6 As Built or installation/layout drawings These are drawings that provide an adequate and accurate record of the installation. The drawings should include particulars of all items, including all wiring and control diagrams necessary to allow for further maintenance, addition or modifications to equipment and system. It is therefore important that during the course of the installation works, the installer should maintain a comprehensively detailed record of all changes from the approved shop drawings to facilitate easy and accurate preparation of the as-built drawings and to ensure that these drawings are in all aspects a true record of the installation. The following details should be included:

the position of all equipments and apparatus the size and type of all cables Type and description of devices used the size and type of conduits, trunking and number of cables enclosed

within circuit identification and spare ways or channels routes of all cables run in ducts and position of any joints schematic and wiring diagrams of systems which are not covered by

drawings elsewhere layout of underfloor and ceiling installations giving accurate locations

of concealed cables the position and number of cable ducts as in the case of underground

installations should be indicated by a cross section showing the disposition of cables laid through each crossing


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1.7 Submission of substation drawing plans Should a substation be required, it will be necessary to pre-consult Power Grid first. This is typically followed up by the submission of substation drawing plans. There are typical substation drawings provided in the How to apply for electricity connection handbook. These typical detail drawings are as shown in the following Figures.

Figure 1.7.1 Plan View of 22 KV/LV Substation


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Figure 1.7.2 Electrical Installation Requirements in 22kV/LV Substation

Figure 1.7.3 Plan View of Cable Chamber 22kV/LV Substation


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Figure 1.7.4 Elevation View of 22kV/LV Substation


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Figure 1.7.5 Sections and details


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Appendix A


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1. Electrical drawings1.3 Types of drawings1.4 Single line diagrams

ed1 and 2 electical drawings and appendix

Documents

installation drawings

types of drawings

cad drawings

installationlayout drawings

engineering drawings

single line diagram

electrical symbols

used symbols