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.
