What is an electrical power system?

Have you ever thought about how you get this “electricity”? How electricity is available almost everywhere?

An electrical power system is responsible for the power generation and distributing it to your house. A power system is a huge complex network in which many types of equipment are applied.

What is an electrical power system?

When various units (generation, transmission, distribution) are combined to form a network that generates and supplies energy to the consumer, that network is known as an electrical power system.

A power system has various units, a generating unit that generates (or converts) electrical energy from another form of energy like thermal energy, nuclear energy, etc.

A transmission unit is responsible for transmitting power from a generating unit to a distribution unit.

Another is a distribution unit, it distributes the stepped-up power to end consumers which may be domestic consumers or industrial consumers.

The structure of the electrical power system is shown below:

Block diagram of the electrical power system.

Let’s understand about these units in details

Various units of electrical power system

The units of an electrical power system are discussed below:

Generation unit

The first section of the power system is a generation unit. The generating unit is responsible for power generation and this power generation is a continuous process.

A power plant is a power generating unit.

A power plant is an industrial area where electric energy is generated.

In power plants, electrical energy is generated from other energy sources.

In this unit, one form of energy is converted into mechanical energy and then the mechanical energy is converted into electrical energy.

Several conventional energy sources used for power generation are coal, water, nuclear, etc. These materials are the primary source of energy which is converted into mechanical energy and then the mechanical energy is converted into electrical energy by a generator.

In India, the majority of conventional power is generated by thermal power plants, hydropower plants, and nuclear power plants.

And to your surprise, thermal power acquire around 85% of total conventional power generated.

Power generation in electrical power system only by conventional sources
Power generation only by conventional sources

The above stats are of only conventional power generation in 2020-2021.

Read the full report of conventional power generation here

The electrical power generated in power plants is low voltage. It ranges from 11kV to 22-25kV. Practical design problems and insulation requirements limit the generated voltage to low voltages. Therefore, step-up transformers are used for the transmission of power.

Transmission unit

The purpose of this unit in the electrical power system is to transfer power from generating station to distributing station using transmission lines.

The power generated in the power plant is stepped up by a step-up transformer is very high. This high voltage is carried by the transmission lines to the sub-transmission unit.

Standard voltage of transmission in india is 11kV, 22kV, 33kV, 66kV, 132kV, 220kV, 400kV and 765kV.

The total transmission line length in India is approx. 428,582 ckm (circuit kilometer). And 400kV transmission line acquires nearly 43% of the total market, followed by 200kV lines.

The highest transmission voltage for AC in India is 765kV. And for HVDC it is 800kV.

pie chart of the voltage level of transmission lines in India. 400kV acquires 43 percent of the market followed by a 200kV line which acquires 42 percent.
The voltage of transmission lines in India

The transmission unit generally operates on extra-high voltage (EHV) and ultra-high voltage (UHV).

Sub-transmission unit

The sub-transmission unit gathers the high voltage from the transmission unit to step it down and supply it to the distribution unit.

Distribution unit

Power distribution is the final and most crucial link of the electrical power system.

The distribution unit is responsible for supplying power from the sub-transmission unit to the consumer (your house). The essential purpose of this unit is to give the consumer, functional level of voltage through the feeder.

The distribution unit is further divided into 2 systems:

Primary distribution unit

The primary distribution unit supplies the power to large power consumers. The voltage required to large consumers is usually 3.3kV, 6.6kV, or 11kV.

Secondary distribution unit

The secondary unit supplies power to residential or low-voltage consumers. It steps down the voltage to a useful value. 220-250V at 50Hz India whereas, 120V at 60Hz for the USA.

Here is the full list of voltage levels for domestic use (link)

Components in electrical power system

A power system is a huge network accountable for numerous different functions. So it requires different kinds of equipment. some of the major components used are listed below:


A generator is a machine that converts mechanical energy into electrical energy. A generator that generates direct current is known as a dynamo. And the generator which generates alternating current is known as an alternator.

In the electrical power system, the generator is used in generating station or power plant. Most power plants in the world use fossil fuels such as coil, gas, oil, etc. to generate electricity.

Read More: How a DC generator works?


The transformer is used to transfer power efficiently from one level of voltage to another voltage level. Both step up and step down transformers are used in electrical power systems.

A Step-up transformer is used to step up the voltage level. It is used at the generating station where low generated voltage is stepped up to a tremendously high level.

Step down transformer is used to step down the voltage level. Before the distribution of the voltage to consumers, the voltage is stepped down to the level which is useable for the consumer.

Transmission lines

Transmission lines are specifically used for the transmission of electric energy from the energy generation station to the distribution unit.

A conductor having a uniform cross-section area is used to make transmission lines.

As very high current flows through the transmission line, it is safe to have a large gap between the ground and the lines. So to make sure the gap between the transmission line and the ground, the transmission lines are supported on a tower.

Quick summary

  • An electrical power system is a network in which power is generated, transmitted, and then distributed to the consumers.
  • The generating station is the facility where electric power is generated
  • The power generated is transmitted to various distribution networks by the transmission unit.
  • The distribution unit distributes the power to the consumers.

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