For electrical devices several tests are mandatory to prove the ability of the device. The tests ensure the required insulating distances between phases, across open switching devices or phase to ground under several environmental conditions of the test object. Therefore, electrical devices are stressed with standardized voltages, which depend on the rating of the device, typically are:

• Power frequency voltage (AC)
• Lightning impulse voltage
• Switching impulse voltage
• DC voltage incl. very low frequency tests
• Partial discharge tests (PD)