single line diagram - electrical

7/26/2019 Single line Diagram - Electrical

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SINGLE LINE DIAGRAM (SLD) Or, ONE LINE DIAGRAM

The single-line diagram is the blueprint for electrical system analysis. It is the first step in

preparing a critical response plan, allowing you to become thoroughly familiar with the

electrical distribution system layout and design in your facility.

WHY ITS REQUIRED?

Whether you have a new or existing facility, the single-line diagram is the vital roadmap for all future

testing, service and maintenance activities. As such, the single-line diagram is like a balance sheet for

your facility and provides a snapshot of your facility at a moment in time. It needs to change as yourfacility changes to ensure that your systems are adequately protected.

To make all the changes documented in a common file, making the electrical system easily

understandable for any technical person inside/outside of the factory.

An up-to-date single-line diagram is vital for a variety of service activities including: Short circuit calculations

Coordination studies

Load flow studies

Safety evaluation studies

All other engineering studies

Electrical safety procedures

Efficient maintenance

WHAT SHOULD BE IN A SINGLE LINE DIAGRAM (SLD)?

A typical package of single line diagram shall include:

Incoming lines showing voltage and size

Incoming main fuses, cutouts, switches, and main/tie breakers

Power transformers (rating, winding connection and grounding means)

Feeder breakers and fused switches rating and type.

Relays (function, use and type)

Current and / or potential transformers with size, type and ratio

Control transformers rating.

All main cable and wire runs with their associated isolating switches

All substations, including integral relays and main panels with total load of each feeder and

each substation

Critical equipment voltage and size (UPS, battery, generator, power distribution, transfer

switch, computer room air conditioning)

A summary load schedule for the LT switchgear panel.

A load schedule for each distribution panels and switch board.

Rating and dimension of bus bar.

All outgoing cables with cable size and type with rating and type of their associated isolating

switches (e.g. circuit breaker). Length and voltage drop of all outgoing cables.

Rating of PFI , changeover, ATS, generators with associated protection and isolating switch

All earthing cable rating (size, type etc.)

All connected load with their individual load capacity.

All spare switches (outgoing circuit breaker) shall be mentioned.

Earthing system must be included with dimension of earthing pit, boring, earth electrode size,

earth lead and ECC cable size and type.

Here is given an example of a typical LT panel one line diagram or Single line diagram (try to follow itas best as possible).


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M

2x1c,1

20.0

mm2Cu.

R=273.4

65KW

Y=273.2

20KW

B=272.4

45KW

TL=819.1

30KW

R=55.2

96KW

Y=55.0

60KW

B=54.2

75KW

TL=164.6

30KW

R=98.6

70KW

Y=98.6

70KW

B=98.6

60KW

TL=296.0

00KW

R=98.6

70KW

Y=98.6

60KW

B=98.6

70KW

TL=296.0

00KW

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'+

,-./,,012

!)3!'**4

567628#19982:528

1x4c240mm2B

YA/NYY

!"!#%&&'()**

'+

,-./,,012

!)3!'**4

567628#19982:528

!"!#%&&'()**

'+

,-./,,012

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567628#19982:528

600A(adjustable)

MCCB


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Sample of load schedule (DB Schedule) (You can follow it or prepare it as your own style)

single line diagram - electrical

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