When your electrical devices are working in their regular way, there might be an exceptional condition, leading to high power. This high power can ruin your device, and can even lead to electrical sparks or fire. Such exceptions should be tested to make sure that your heavy electrical equipment works correctly under every condition.
To make sure that your devices work properly under heavy power conditions, high voltage testing is done. In this testing, an HV testing unit is used. This unit is capable of producing high voltage, which is directly applied to your devices to see how they perform. If they do not break down under heavy power load, it means they are doing well and are safe to use.