What is ground resistance?

As a safety measure, all electrical devices must be connected to a direct path to the ground and this path is usually supplied with a conductive rod blown into the ground. The ideal system would have zero ground resistance, which is the amount of electrical resistance that this path to electricity flow. However, no system is ideal, so there is always a small amount. Regulatory agencies have different standards concerning the maximum acceptable value for ground resistance to ensure the safety of equipment and operators, but the US National Electric Code (NEC) and the telecommunications industry specify 5 Ohms as the maximum value.

Dependent on three factors depends on three factors. These include the resistance of the ground rod, the contact resistance between the rod and the surrounding earth and the resistance of the surrounding body of the Earth. The ground bars are usually made of high -conductive material, so their resistance is very low and the contact resistance is frequently, provided there are no contaminants such as color or ointmentnote. The country surrounding the rod usually provides the highest resistance, but the resistance of countries decreases with increasing distance from the rod.

Before measuring the ground land resistance, soil or land or ground resistance is tested, it is usually done with a series of four evenly distributed bets. The current is applied across the farthest pair of bets and a drop in voltage over the inner pair is measured by a ground resistance meter. The meter is calibrated so that it automatically transforms the voltage to resistance, measured in the ohms. The ground resistance meter also automatically selects the test frequency with the least amount of noise to compensate for the surrounding ground currents and their harmonious.

There are three ways to perform a ground resistance test around an existing origin. In the first, called Potential Measure fall, a current between the grounding rod that has been disconnected from its connection, and the share, and the voltage drop with meRome at the second bet located in the middle between them. The second method, called selective measurements, is similar, except for the clamping ring, is applied to the rod, so it does not have to be disconnected. In the third method, called without a stable, the resistance of ground resistance is determined by two clamps located around the ground rod or connecting wire. It is the easiest to do, because it does not include driving shares, but it only works in systems that have more than one ground bar.