What is Substation Design in Power Distribution System?

Substation is a set of several electrical components used to change characteristics of electric power supply. For example, a substation is used to change the voltage, frequency, ac to dc, etc. It can be operated as transmission or distribution purpose. Substation design depends on different purpose of its activity. There are many different types of substations like – 

• Transmission substation,

• Distribution substation,

• Collector substation,

• Pole mounted substation, etc.

There are several components to design a substation. Substation design parameters are like-

·         Transformer

·         Circuit breaker

·         Isolator

·         Bus bar

·         Lightning arrestor

This section will provide information about the different components of a substation design.

A transformer is an electrical component which step up or step down voltage. Ideally, there are two windings in a transformer called primary winding and secondary winding. Primary winding voltage is denoted by (Vp) and secondary winding voltage is denoted by (Vs). The input current passes to the primary winding and the output is taken from the secondary winding. There are two types of transformers. They are-

• Power transformer

• Instrument transformer

Circuit breaker is one of the most important electrical components which can interrupt automatically in a circuit to prevent fault condition. Fault conditions are excess current flow, over voltage, overload, high speed, over and under frequency, short circuit, etc. When fault condition occurs, relays are used to sense the fault and send a signal to the circuit breaker. Then the circuit breaker closes the operation. They are as follows-

• Oil circuit breaker,

• SF6 circuit breaker,

• Air blast circuit breaker,

• Magnetic circuit breaker, etc

Relay is an electrical switch which is used to open or close a circuit. When a relay operates in a normally open condition, it means the contact is open when relay is not energized. Again when the relay will energize then the contact will closed.  Relays are used on both sides of the circuit breaker. Relays are very useful for protection and the relay panel is operated by DC power supply. There are different types of relay such as Percentage differential relay, Impedance type distance relay, Induction type relay, Classical relay, and Pilot relay, etc.

When a circuit breaker trip under abnormal condition, it is recommended not to touch any part of the electrical circuit for safety reasons. So it is very important to keep in mind about isolator during designing a substation. Isolator disconnects the faulty part for repair. An Isolator can be operated manually, by hand, or using remote control. It is not a switch but it isolates a section from any energized conductors. 

Lightning arrestor is an electrical component that protects other equipments from lightning. Lightning arrestor has two terminals - a high voltage terminal and a ground terminal. High voltage is connected to the equipment and ground terminal is connected to the earth. During lightning very high voltage passes to the ground through the lightning arrestor.

Bus bar is used to carry a very large current or to distribute current to multiple devices within switchgear or equipment. Substation is designed such a way where bus bar like single bus bar, double bus bar, double bus bar with reserved bus bar, ring bus bar, etc.