Grounding or Earthing System

Earth Continuity Conductor or Earth Wire

That part of the earthing system which interconnects the overall metallic parts of electrical installation e.g. conduit, ducts, boxes, metallic shells of the switches, distribution boards, Switches, fuses, Regulating and controlling devices, metallic parts of electrical machines such as, motors, generators, transformers and the metallic framework where electrical devices and components are installed is known as earth wire or earth continuity conductors.

The resistance of the earth continuity conductor is very low. According to IEEE rules, resistance between consumer earth terminal and earth Continuity conductor (at the end) should not be increased than 1Ω. In simple words, resistance of earth wire should be less than 1Ω.

METHODS OF EARTHING:

Earthing can be done in many ways. The various methods employed in earthing (in house wiring or factory and other connected electrical equipment and machines) are as follow:

Plate earthing:

Plate earthing is the way of connecting a non-current carrying part of an electrical equipment to the ground.

In plate earthing system, non-current carrying parta is a plate which is made up of either copper or galvanized iron.

If copper is used for plate earthing, it’s dimensions should be 60cm x 60cm x 3.18mm (i.e. 2ft x 2ft x 1/8 in). The dimension should be 60cm x 60cm x 6.35 mm (2ft x 2ft x ¼ in) for galvanized iron (GI) type plate electrode.

The plate electrode is buried vertically towards the earth (It is named as earth pit). The earth pit should be placed 3m (10ft) from the ground level.

Pipe Earthing:

A galvanized steel and a perforated pipe of approved length and diameter is placed vertically in a wet soil in this kind of system of earthing. It is the most common system of earthing.

The size of pipe to use depends on the magnitude of current and the type of soil. The dimension of the pipe is usually 40mm (1.5in) in diameter and 2.75m (9ft) in length for ordinary soil or greater for dry and rocky soil. The moisture of the soil will determine the length of the pipe to be buried but usually it should be 4.75m (15.5ft).

Rod Earthing:

It is the same method as pipe earthing. A copper rod of 12.5mm (1/2 inch) diameter or 16mm (0.6in) diameter of galvanized steel or hollow section 25mm (1inch) of GI pipe of length above 2.5m (8.2 ft) are buried upright in the earth manually or with the help of a pneumatic hammer. The length of embedded electrodes in the soil reduces earth resistance to a desired value.

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