Equipment Used in Substation

Equipment Used in Substation

The substations used to distribute power in different areas. In this article, we will discuss different equipment used in substation.

The below list is the equipment used in substation.

  • Bus Bar
  • Transformer
  • Circuit Breaker
  • Isolator
  • Fuses
  • Lightning Arrester
  • Insulator
  • Earthing Switch
  • Shunt Capacitor and Reactor

Bus Bars

  • The term ‘bus’ is derived from the word omnibus which means a collector of things. Bus, therefore, refers to the main collectors of electrical energy which may be bars, rods, tubes, or channels.
  • An electric bus collects electric energy at one location and the bus bar is the conductor through which the current flows.
  • The materials normally use for bus bars are copper and aluminum.
  • Outdoor bus bars are generally mounted horizontally insulated from the earth by post insulators made of porcelain.
  • Outdoor bus bars are widely spaced to prevent birds with a large wing spread causing short circuits of the buses.
  • Indoor buses may be open or closed.


  • A transformer is a static device. It used to transform power from one voltage level to another voltage level without changing the frequency. The transformer can be classified into two kinds:

(i) Power transformers
(ii) Instrument transformers

  • Power Transformers: Step-up transformers used at generating stations to step up the voltage for transmission, whereas step-down transformers used at receiving end stations to step down the voltage for secondary transmission, and primary and secondary distribution.
  • An instrument transformer used for metering and protection.

Circuit Breaker

  • A circuit breaker is a device that can interrupt a section or a circuit automatically if an abnormal or faulty condition exists in that section.
  • Under the normal operating condition, the contacts of each pair close on themselves, and the circuit breaker said to closed. In the event of any abnormal situation, the movable contact of each pair made to open against spring forces by a mechanical device through a trip circuit energized by a battery.
  • The trip circuit actuated by one or more relays that sense the abnormal condition.


  • Isolators used for isolating the circuit when the current has already interrupted.
  • An isolator is a manual or motor operated disconnect switch.
  • They are provided for isolating all circuit breakers for maintenance and repair.
  • Isolators also used for disconnecting lines and allow the equipment to taken out of the system for repair, maintenance, and testing.
  • Isolators help to have a sectionalized bus system. It not supposed to opened.
  • Under loaded conditions and for this reason, interlocked with circuit breakers to prevent operation on load. However, these are capable of dealing with small charging currents. Isolators on the line side of the line circuit breakers should equipped with grounding blades.


  • A fuse is a non-adjustable, direct-acting, single-phase device that responds to both the magnitude and duration of current flowing through it.
  • Fuses may used both in low voltage and high-voltage lines. Fuses are protective devices.

Lightning Arrester

  • All the equipment in the outdoor station should protected against direct lightning strokes and traveling waves reaching the station over the transmission lines.
  • Surge diverter bypasses the surge voltages to earth, thus holding the voltage across the protected insulation to a safe value.
  • For important equipment, station type lightning arresters used. Arcing horns or rod gaps used for less important insulation.
  • For example, transformer insulation should protected by a lightning arrester, while the transformer bushing insulation may protected by a rod gap and an isolator may be equipped with an arcing horn.


  • Porcelain insulators used in substations to support and insulate the live conductors and bus bars.

Earthing Switch

  • It connected between the conductor and earth.
  • Normally, it is in an open position. However, when the line is disconnected, this switch closed to discharge trapped charge to the ground.

Shunt Capacitor and Reactor

  • These capacitors supply reactive power to the loads and thus help in improving the power factor.
  • Sometimes, reactors may also be used to absorb reactive power supplied by the line.

So, these are the equipment used in the substation.

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