Withstand voltage testing is used to check whether a given electrical product or part provides sufficient dielectric strength (i.e., insulation strength) for the voltages to which it may be exposed. 

According to the Japanese Industrial Standard JIS C 1010-1:2014, which stipulates the safety requirements for electrical equipment for measurement, control, and laboratory use, the test voltage used by a withstand voltage tester is based on the main power supply’s specifications as follows:

(1) The supply voltage of the device being tested (for example, 100 to 240 V AC, etc.)

(2) The overvoltage (measurement) category of the device being tested (for example, CAT II, CAT III, etc)