What is single line diagram (SLD)?


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Single Line Diagram

During the preliminary project designing of any project,the key diagram used is the single line diagram (SLD) also called the one line diagram and a number of subsidiary signal line diagrams.

The set of single line diagram form the basics of all electrical work carried out in a project.

The SLD shows all pertinent information about the sequence of the circuit,but does not give as much detail as a schematic diagram.

The purpose of single line diagram is to show sources of power,electrical equipment,electrical drives,system details and fault levels.

What is a Single Line Diagram (SLD) ?

It is a drawing that shows by single lines and symbols a simplified layout of a three-phase electrical system.

Single line or one-line diagram get their name form the fact only one phase of three phase system is shown and only one line is used to represent any number of current carrying conductors.

Standard symbols are used to represent components of power systems,such as transformers,circuit breakers,generators,fuses and switches.

Information provided in a SLD

Incoming cable size/sources detailed marked.
If through bus-duct,symbols and ratings marked.
Type of switching device and nominal rating.
CT/PT ratio,burden and accuracy class
Instruments
Relays
Earthing of incoming / outgoing feeders
Surge arrestors for incoming feeders
Legend / Legend drawing reference
Board designation
Device designations

<img src="/uploads/default/original/1X/f59687cf03d358431c3ce16efc3940d03b386f99.jpg" width=“387” height=“434” alt="Electrical Drawing - Single Line Diagram’>