Substation, An introduction and types

Substations are installations in a Transmission and Distribution System which are involved in the connection of different sections of the transmission and distribution system, usually with the transfer of electrical power from one voltage level to another.

Substations play a vital role in integrating the generating, transmitting and distributing parts of an electrical system.

A substation is generally located in an open area. The substation contains of numerous equipments such as transformers, breakers, capacitors, measuring and protection devices and so on.

Based on their functions, Substations can be classified into four types
  • Distribution Switching Substations
  • Switching Substations
  • Transmission Substation
  • Customer Substation
Distribution Substations
Distribution Substations are substations which reduce the voltage from the Transmission level, say, 132 kV to a lower level such as 66kV or 33kV. The power at this reduced voltage is then supplied for domestic consumption via distribution transformers which are located in each street. These transformers then reduce the voltage to 440V and so on.

Customer Substations
These are substations that cater to only one big consumer, usually an industry. Industrial consumers though draw power directly usually at the secondary voltage level of the distribution i.e. 66kV or 33kV

Switching Substations
These substations are involved in switching. A power system may contain numerous feeders at the same voltage levels, the switching of these feeders for maintenance and the isolation of faulty feeders is vital to the reliable functioning of the system. The Switching Substations are used in merging two or three feeders into a single feeder. Switching substations contain all the components of a substation other than transformers. such as surge arrestors, current and voltage transformers, isolators,etc.

Transmission Substations
These are substations that are connect two transmission lines. The voltage levels in these substations are 66kV or higher. Usually these substations have transformers which connect two voltage levels. The substations also contain regulating equipment such as phase-shifting transformer, VAr compensators, reactors, etc. Elaborate arrangements are made for isolation of sections of the substations for maintenance in a manner that there is no interruption to the power supply.

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