What is an electrical substation?
How does it work?

What is an electrical substation?

A substation is a facility to control electricity power and it transforms voltage from high to low or the reverse as well as transforming electric frequency.

A substation may contain transformers to change voltage, circuit breakers to cut off automatically the electric power, lightning arresters to divert the electric surge from the lightning to the ground, and so on.

In most cases, substations are located away from plain area where consumes a lot of electricity.

In such case for long distance electric power transmission, it is transformed to high voltage to save electricity loss.

Then, it is transformed to lower voltage in order of ultra-high voltage substations, primary substations, secondary substations, distribution substations, and finally to factories or houses.

Purpose and role of substations

1. Step up voltage to high for higher electricity transmission efficiency on long distance transmission.

2. Transform voltage to suit for each usage.

3. Connect or cut electricity lines according to necessity.

4. Distribute electric power to each places (ex. railway, factories, buildings, houses, etc.).

Flow of voltage transformation and power transmission

1. Substations inside (or alongside) the power station

* Step up voltage from the power station output (approx.20kV) to ultra-high voltage from 275kV to 500kV.
* Transmit electricity to Ultra-high voltage substations.

2. Ultra-high voltage substations

* Step down the ultra-high voltage transmitted from the substation in the power station to 154kV.
* Transmit the electricity to primary substations.

3. Primary substations

* Distribute 154kV electricity to railways or large factories.
* Step down the voltage to 66kV and transmit to secondary substations.

4. Secondary substations

* Step down 66kV to 22kV.
* Distribute electricity to factories
* Transmit the electricity to distribution substations.

5.Distribution substations

* Step down 22kV to 6600V
* Distribute electricity to factories or offices
* Transmit the electricity to

6. Pole transformers

* Step down 6600V to 200V or 100V
* Distribute electricity to houses or small offices

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