Components / Parts of Earthing System

Components / Parts of Earthing System Points : components / parts of earthing system, earth continuity conductor, earth lead or earth conductor, earth electrode (1) Earthing Continuity Conductor
(2) Earthing lead or Earth Conductor
(3) Earth Electrode 1. Earth Continuity Conductor This is the part of the earthing system, which joins or bonds together all the metal parts of an installation: Conduits, ducts, boxes, metal casings of switches, fuse distribution boards, regulating and controlling apparatus exposed metal work of machines and any metal frame work on which electrical apparatus is mounted.

I.E.E. regulations (E3) requires that where earth leakage protection depends on the operation of fuses or excess current circuit breakers the impedance or resistance between the consumers earthing terminal and the remote and of every earth continuity conductor should not exceed one Ohm. In practice it should be lower than 01 Ohm, since a fault nearly always has impedance and so the resistance of the earth continuity conductor must be lower to take account of this. 2. Earth Lead or Earth Conductor The earth conductor is the conductor, which provides connection between earth electrode and earth connecting point (Main Earth Point). The earthing conductor must be short and straight with the minimum number of joints. Two forms of earthing conductors depending upon the load, are commonly used. These are copper wire and copper strip. Copper strip is used on very large installations.

The usual practice in Pakistan is use to hard drawn copper wire. In case of copper wire duplicating earthing conductor should be run up to the earth electrode in order to increase the protection of installation. If there are two earth plates there should be four earthing conductors. The area of each of the earthing conductor should not be less than half the area of the largest current path.

When copper wire is installed, it should be enclosed in the G.I Pipes. This gives protection against mechanical damage and corrosion and also can be used to guide water to the plate in order to keep the plate and surrounding artificially damped. 3. Earth Electrode An earth electrode provides connection between the installation metal work and general mass of earth. For domestic installation main water pipe was used as earth electrode. Big installation (over 21 kW) has to have its own earth electrode. The most common type of electrode is plate of either galvanized iron or copper. Cast iron pipes can also be used in place but are not as efficient as plates. The main purpose of an electrode is to provide good conductivity with earth at all time. The way is to install the electrode well below water level. The plate should he placed in an upright position and surrounded by a bed of at least on ft. of charcoal mixed with lime or salt. This effectively increases the size of the plate and thus increases continuity with earth. The plate must rest, at least one foot below the permanent water level.