Good conductivity

Measuring equalising connections in the earthing system shows that the connecting cables are whole and have good connectivity, so that no potential differences can occur in the electrical facility. It is important information that is included in the calculation of contact voltages.

Recommended measuring method

Earthing connections and main earthing connections are measured with the help of the injection method, which is a four-point method. A high current is forced and the voltage drop is measured. This provides a basis from which to calculate resistance with high resolution and great accuracy. Measurement of a high current in the circuit and separate measurement of the drop in voltage provides an accurate result for the resistance in the loop. Trainor uses advanced test instruments with a measuring range down to 0.1 µΩ and test currents up to 600 A. The test loop can be pole changed to investigate whether unintended values affect the result.

Formal requirements

If the earthing system is a part of a wider earthing system (global earthing system), there is no requirement to measure transition resistance in a high voltage system. Nevertheless, it must be fully documented that the earthing system is coherently conductive and has adequately good connections. One method to check this is to apply an adequately high test current to the circuit, measure the voltage drop and calculate the circuit's resistance.

Benjamin Abrahamsen

Benjamin Abrahamsen

Project Manager - Control and Measurement

+47 917 06 217

Ivar Andre Toms

Ivar Andrè Toms

Team Leader - Control and Measurement

+47 986 04 365

Vegard Sjoblom

Vegard Sjøblom

Project Engineer - Control and Measurement

+47 907 78 054