Distribution of electricity in a large or medium

DISTRIBUTION OF ELECTRICITY IN A

LARGE OR MEDIUM SIZED

BUILDINGSUBSTATION AND

ELECTRICITY LINES

BY: IQBAL NURFARIQ B. OTHMAN

INTRODUCTIONThe amount of electricity needed by large buildings such as office,high rises building and shoping complex are relatively high because of the presence of building services equipment in these premises. The following are parts of electricity distribution systems of a medium and large building.

SUBSTATION Any building that require an amount of

electricity more than 1.5MV or if TNB request it, need to served by its own substation.

The substation is build separate from the building or in part of the ground floor of the building and the building owner need to maintain it.

Contents of the substation:Transformer. This steps down the high voltage electricity to the

low voltage electricity.

High Voltage Switch Board (and sometimes) Low Voltage Switch Board. This is for isolating and switching purpose. The switch board provide protection againts

overcurrent.

Metering equipment. This is to measure the consumption of electricity.

Automatic gas fire extinguisher systems and fire detactor.

This systems function is to automatically put out any electrical fire in the substation.

Fire detector is connected to the building fire alarm systems.

ELECTRICITY LINES

In order for the electricity to be distributed with in the building, it need to travels through lines.

The following explains features of these electricity lines systems and element.

CONDUCTORS: Usually made to a small extent aluminium or

copper. To conduct the electricity. Cable are used to conduct the electricity from the

power station to the user. Wires are used to distribute the electricity to the

building.

INSULATION: Used to prevent short-circuiting, electrocution or

fires. The wire or cable are sheathed by a non-

conductive material such as rubber. High voltage cable are sheathed in a mineral

material, than by a metal covering, than finaly sheathed by a plastic or rubber covering.

BUS BAR: Consist of 4 thick aluminium or copper strips. Conduct electricity within a switchboard,

distribution board, substation or other electrical apparatus.

Each of the 3 metal strips contain 240V single phase current, and the fourth strip contain earthing line.

Riser bus bar is to deliver the electricity through a trunking which run up in electricity cable through the height of a tall building.

CABLE AND WIRING HOUSING: Give protection to the insulation and the conductor

and also to aid maintainance. Usually use plastic pipes known as conduits and

for metal is known as cable trunking.

END~~~

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