Thursday, April 22, 2010

Power System Network

A detailed explanation of the conversion and distribution of electric energy from the power station to consumer units.This post describes how electric energy moves from the power generating station through conductors of various sizes to consumers premises.To minimize losses and for economical reasons, electrical energy has to be converted into different magnitudes during transmission and distribution until the consumer load.

In most countries, electrical energy is generated at 11kV, 33kV. It is generated by 3phase alternators in parrarell. The electrical energy produced at the power station is Alternating Current (AC). AC is preferred for transmission because it can be stepped up and down and with ease and efficiency. With AC, the maintenance of substations is easier and cheaper as compared to DC. With the help of a step-up transformer, electric current is stepped up to 132kV, 220kV and 400kV. Power is stepped up for transmission so as to reduce losses during transmission and saving conductor material. High voltage transmission lines are used to transmit this heavy current from the generating station to transmission substation.
Power Generation Statistics:
India-11kV, 33kV
Kenya-11kV, 33kV

The high voltage line terminates at a distribution substation. The substation receives voltage at 400kV, 220kV, 132kV or 66kV with the help of large 3phase step-down transformers. The substation is capable of transmitting 6.6kV,11kV, 33kV and 66kV  through different feeders depending on the target load. The common 11kV line runs along important roads of the city. Large consumers being fed by 33 and 11kV have their own substations for stepping down this voltage.

These are the most common facilities in the electric power system. They provide distribution circuits that directly supply most electric consumers. The pole mounted transformers are of this category. They receive voltage of up to 11kV or 33kV and step it down to 415/240V (Kenya). As opposed to primary distribution substations, the secondary ones do not have complicated equipment since they handle a smaller amount of current. They are located near neighborhoods and are likely to be encountered by the customers.

Depending on the type of load of the consumer, Single phase/3phase will be supplied from the distribution line by connecting appropriately. Single phase shall be supplied to small consumers at 240V while 3phase shall be supplied to large industrial consumers at 415V. At the consumer intake, the power supply company provides the Energy meter depending on the tariff

The CCU is the point where the power is distributed throughout the consumer’s premises via fuses, conductors and circuit breakers. This however is not supplied by the power distribution company. Current in the premises is controlled at this point which has a single gang isolator switch to isolate the entire premise.


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  2. Electrical transmission system is the means of transmitting power from generating station to different load centres.
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