Page 14 - Practical Power System and Protective Relays Commissioning

Chapter 2

Substations

2.1 INTRODUCTION
A substation is a junction point in a distribution or transmission system.
Substations are used to:
Switch circuits to control power flow
Isolate faulty sections of the system
Split the system to maintain fault levels
Provide system flexibility
Substations can be one of two types:
1. Air insulated substation (AIS)
2. Gas insulated substation (GIS)

2.2 SUBSTATION ELECTRICAL DIAGRAMS
Substation electrical diagrams includes single line diagrams (SLD) that
represent the three-phase wiring diagram by using a single wire diagram.
This is because the three phases are similar. You may also come across
diagrams that represent protective relays in more detail, called protection
SLDs.

2.2.1 Single Line Diagram
A SLD shows the overall relationship between components of electric cir-
cuits using single lines and graphic symbols, for example that shown in
Fig. 2.1. An example of a protection SLD is shown in Fig. 2.2.

2.2.2 Schematic/Elementary Diagram

A schematic or elementary diagram shows the electrical connections and
functions of specific circuit. These can be seen in Fig. 2.3 (AC schematic
elementary diagram) and Fig. 2.4 (DC schematic elementary diagram).

Practical Power System and Protective Relays Commissioning.
DOI: https://doi.org/10.1016/B978-0-12-816858-5.00002-2 9
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