Testing the earthing system of a lightning protection system is an important measure to ensure it is functioning effectively and safely. Each conductor has its own electrode termination and the resistance to earth of the whole system must not exceed 10 ohms, as recommended by BS 7430 – the Standard for earthing electrical installations. During the test, the condition of all the conductors, joints, bonds, earth electrodes and terminations should be checked, and the results noted.
The checks that must be made include testing the resistance to earth of the earth termination network as a whole. In addition, each individual earth electrode must be tested. The stringent testing is carried out by our skilled team, who follow strict safety procedures, disconnecting and testing only one earth electrode at a time.
The resistance of each individual earth electrode is tested and measured while it is disconnected from the system and the results recorded. The common method of measurement is the “Fall of Potential” method. It involves passing a known current between the earth electrode and the test electrode.
Using the relevant equipment, the resulting voltage is measured. These values enable the earth electrode resistance to be calculated, using measuring instruments that indicate the earth electrode resistance directly.
If the lightning protection system’s resistance to earth exceeds 10 ohms, or if one individual electrode’s resistance exceeds 10 ohms when multiplied by the total number of electrodes, it is necessary to reduce the value. In cases where the resistance is lower than 10 ohms, but higher than the previous reading, it’s important to investigate the cause and take remedial action if required.
A visual check is also carried out on all conductors, joints and bonds and their measured electrical continuity. The results of all the tests must be recorded in the lightning protection system logbook for future reference. For general maintenance and safety purposes, tests should be carried out at regular intervals, not exceeding 12 months.
The standards for the earthing system are set by law and require design limits to be met. All of the tests carried out by Lightning Strike are compliant with the British Standard BS EN 62305.