In all power generation, transmission and distribution systems, it is generally necessary to install an electrode or electrode assembly in the ground to ground the plant and the equipment in it. This work is generally called earthing. In this way, a return path to the fault current is shown in case of problems in the electrical energy system. Grounding can be done in various ways. However, the grounding system must not show high resistance. Otherwise, the tension on electrical machines and equipment cannot be transferred to the ground and this creates a danger to human life and property safety.
Therefore, in order to avoid potential problems in the electrical system or to minimize possible damages, the grounding resistances of the existing plants, transformer stations or transformers must be measured at regular intervals within a program. As a result of these measurements, the grounding resistance levels above the limit values must be reduced to normal values.
The accepted grounding resistances for various electrical devices are as follows: 1 Ohm in large power plants and transformer stations, 10 Ohm in secondly important installations and transformer stations and 5 Ohm in all other power stations and transformer stations.
Megger device is widely used for measuring earth resistance. This device is based on AC voltage drop during operation. The Megger device sends an alternating voltage to the ground that is different from the mains voltage frequency. Measurement is made by monitoring the voltage with the same frequency taken from the ground. During the measurement of soil resistance, auxiliary earthing is done in the soil. Conventional earth meters have three electrodes: earth electrode (E), current electrode (C) and potential electrode (P). However, two piled measurement forms are more widely used.
Our company, within the framework of electrical safety examinations, earth resistance measurements in accordance with the relevant regulations, standards and test methods published by domestic and foreign organizations. The following standard is taken into consideration in these studies:
- TSE K 187 Neutral earthing resistors
In the meantime, TSE continues to work on the following two standards:
- TST 2017114895 Neutral grounding resistors
- TST 2016114274 Measurement methods and evaluation of resistivity and grounding resistance in electrical systems (Electrical) (studies are continuing on this standard)