Measurement of the earth resistance is a necessary condition for the stable operation of the electrical installation

Measurement of grounding resistance is a mandatory requirement for the installation and operation of electrical appliances, as stipulated in the operating rules and fire safety instructions.

There are several different methods for making earth resistance measurements, chosen by a specialist, depending on several factors, such as the nature and conditions of the measurement, the values of the resistances to be measured, the relative accuracy and the speed of the measurements.

Measurement of the ground resistance is made to examine its condition. The process of taking measurements is carried out in several stages:

• The visible part of the ground is examined, namely: the ground loop is checked, the connection of the grounding devices to the electrical network is reliable. Carefully examine the place of connection of wires and grounding details. Cracks on weld joints of joints and easing of bolts of fastening are not supposed, and also conformity of examined grounding to mounting rules is checked.
• Preparatory work for the measurement is in progress. These include the creation of an artificial current circuit, for which no less than 40 meters from the grounding device is installed an auxiliary earthing device , connected by a wire to a measuring instrument. The second electrode, called the potential electrode, is installed similarly to the auxiliary electrode, not less than 20 meters away, and is also connected to the measuring device by means of a wire.
• The final step is to measure the resistance of grounding devices, for which the wire is connected to a measuring device and a grounding electrode, and then the resistance of the circuit is directly measured.

The earth resistance is measured using special devices that use the principle of potential drop created by alternating current between the electrodes, one of which is called potential, the second is auxiliary. Based on the results of the measurements of the grounding device, a protocol is drawn up, on the basis of which a conclusion is made about its serviceability and the admission of the electrical installation to operation.

It is noted that only in dry weather with minimum air humidity, soils have the highest resistivity values , and that is why it is recommended to use such weather conditions when planning the measurement of ground resistance. Of course, such work is carried out in any weather and at different times of the year, for which there are regulatory seasonal factors that take into account the weather factor in calculating the resistance. If we talk about the timing of their conduct, then annual check of grounding resistances of electrical installations is provided, and after performing repair work or reconstruction of grounding.

Specialists who have received special training, who know how to check the grounding and have the appropriate electrical safety approval, are involved in these works.