In the context of operations on installations connected to the electricity distribution network, it is
recommended to perform these measurements with the power off (EN 50110-1) to prevent electrical
hazards.
The installation is made safe and the power is switched off by means of a procedure called
Separation.
A specific instrument compliant with the IEC 61243-3 standard must be used to check the actual
absence of any voltage: a Voltage Detector.