single line diagram - electrical
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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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7/26/2019 Single line Diagram - Electrical
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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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567628#19982:528
1x4c240mm2B
YA/NYY
!"!#%&&'()**
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567628#19982:528
!"!#%&&'()**
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600A(adjustable)
MCCB
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7/26/2019 Single line Diagram - Electrical
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Sample of load schedule (DB Schedule) (You can follow it or prepare it as your own style)
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