What is Substation & how does Substation work? 6 Important Points

By December 23, 2020January 8th, 2021Civil Engineering, Pway / Railways, Road Lighting
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You must have seen local substation that supplies electrical power to your home or power to road lighting columns of your local area, but do you know what is a substation and how does a substation work?

Please read this blog for details.

What is Substation?

The substation is used to transmit the voltage low to high or high to low and then distribute it to the power centres. The electric power needs to transmit to a great distance; therefore, it is transmitted with a high voltage and low current level to minimise the transmission losses.

Substation comes with various supporting devices such as fuses, circuit breakers, etc to protect and distribute the power in the most efficient way. Substations are normally placed in an open environment within a closed fenced compound.

Function of Substation

Following are the Key function of the Substation:

Stepping up and down the voltage:

As stated above Substation are used to step up the voltage and lower down the current for transmission first, then the voltage is stepped down for distribution to deliver the current to the households and business units.


Switches are provided to disconnect the network and/ or feeder circuit from the main power system. The disconnection process takes place to isolate the associated equipment of substation from the network. It is required when there is a high demand and switching of voltage would potentially be a dangerous task.

Power Cuts:

In case of huge power demand, substation, power network and associate equipment’s would face significant overloading, as a result, Power Cut takes place to protect the network.

Protection System:

It works as a protection system with the help of fuses and circuit breakers.  It helps to protect power supply equipment’s against peak demand and short circuit situations.

Types of Substation

Following are the key types of Substations:

  1. Transmission Substations
  2. Distribution Substations

 Transmission substations

Transmission substation caters high voltage transmission lines and transmits the power to delivery points in bulk. The substation also comes with capacitors to control the high voltage and voltage fluctuation.   Circuit breakers and fuses are used to isolate the power network in case of heavy power loading.

Transmission Substations generally connect to multiple parallel networks, called as Transmission Grid to generate high volume power system and transmit to various end-users source points through dispersal centres.

Transmission Substations are further classified into two categories:

  • Dual Source Transmission Substation
  • Single Source Transmission Substation

Dual Source Transmission Substation

In the case of Dual Source Transmission Substation, fault in the power network doesn’t impact the transmission. Means, the alternate source takes control of the transmission process and primary source gets to recovery mode. When both sources work together, they can supply the power to multiple destinations.

Single Source Transmission Substation

In the case of Single Source Transmission Substation, fault in the power network does impact the transmission, as a result, it temporarily stops the transmission. That’s why Single Source Transmission Substations are less dependable and so they are not recommended where bulk power transmission is required.

Distribution Substations

Distribution Substations are used to handover power from the transmission system to the diffusion system.

These Substation controls the voltage to carry forward the power to the transformers and then to the end-users. It is also equipped with circuit breakers and fuses to isolate the network in case of any overloading or technical failure.

Distribution Substation functions with the voltage ranging from 0.4KV to 11KV and distribute power to the end-users such as residential units and business or industrial units.

Traction Power Substation for Railway or Pway:

Traction Power Substation takes Alternate Current (AC Current) from the service providers and converts it to Direct Current (DC Current) to use it for Railway or Pway as a power source. The location of Traction Power Substation depends on the geometric layout of Pway network and surrounding topographical constraints. The demand for power supply in peak hours, Pway longitudinal gradient, and Speed of Pway are key parameters to determine the location of the substation.


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Distribution Network Operators (DNOs) for Road Lighting and Traffic Signals:

Road Lightings and Traffic Signals are connected to local Distribution Network Operators (DNOs) that takes power from the Substation Transmission System. All road lightings, traffic signal systems are connected with the DNO and controlled by a remote-controlled centre to effectively manage and execute the power supply.

Generally, the power supply of to the road lightings columns, signals, etc are unmetered because it would not be financially viable to connect each lighting and signal column to a meter, therefore a separate mechanism is used to calculate the power usage.

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Substation Apparatus:

Following are key Substation Apparatus that are commonly used to transmit, distribute, control and regulate Power System:

  1. Transformer
  2. Isolators
  3. Circuit Breaker or Fuses
  4. Switches
  5. Earthing Systems
  6. Busbars
  7. Protective Relays

I hope this blog provides you with a deep inside of Substation, its purpose and functioning. Please feel free to like, share and comment.

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