EARTH RESISTANCE TESTING

Hey guys,

here i got something interesting to share bout earth resistance testing :)

1) Why need to do grounding in the wiring system?

In electrical supply system, an earthing or grounding system defines the electrical potential of the conductors relative to that of the Earth’s conductive surface.

The main purpose of doing grounding in the wiring system is to provide protection against electrical shock. Where a protective Earth (PE) connection ensures that all exposed conductive surface are at the same electrical potential as the surface of the Earth, to avoid the risk of electrical shock if a person touches a device in which an insulation fault, a very high current flows, which will trigger an over current protection device such as fuse or circuit breaker that disconnects the power supply. Therefore, the choice of earthing system has implication for the safety and electromagnetic compatibility of the power supply.

2) What are the measures to be taken if the value of the earth resistance is very high?

Some of the measures that could be considered if the value of earth resistance is very high are as below:

a) Position or Install Electrode on the Moisture Content of the Ground

The increased in moisture content of the ground can rapidly decrease its resistivity. It is especially important to consider moisture content in areas of high seasonal variation in rainfall.

b) Chemical Position

Certain minerals and salts can affect soil resistivity. Their levels can vary with time due to rainfall or flowing water. However, although the additional of salts can lower soil resistivity, they are not recommended due to corrosion and leaching.

c) Electrode Dimension

Electrode dimension is referring to the size and surface area of an electrode. The most important dimension to consider when designing an earth electrode is length. The greater the length of an electrode, the lower the density of the current in soil in the immediate vicinity of the electrode. Hence this could lower resistivity.

d) Area Available or Installing Electrode in Parallel

Installing a number of electrodes in parallel could lower the resistivity. Which means the combined resistance is the practically proportional to reciprocal if the number employed.

e) Earth Electrode Materials

The resistivity is influences by using the right earth electrode materials. This is because the quality of earth rods are commonly used from either copper, stainless steel or copper bonded steel. Mostly the copper bonded steel cord rod is the most commonly rod used due to its combination of strength, corrosion resistance and comparatively low cost.

Whereas solid copper and stainless steels rod offer a very high of corrosion resistance at the expense of corrosion resistance at the expense of lower strength and high cost.

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Regards,

amy_ME