Electrical properties of insulating materials under VLF voltage

Very low frequency (VLF) AC voltage testing in the frequency range from 0.01 to 1 Hz is increasingly being used for both high voltage (Hi-Pot) acceptance and condition assessment of installed large capacitance power components. Mainly due to the low amount of reactive power needed, allowing more compact test equipment compared to that at power frequency.

The main purpose of the CIGRE WG D1.48 was to review the present knowledge regarding the effects of VLF voltage testing on electrical properties and ageing mechanisms of high voltage insulation systems, aiming at facilitating development of valid methods and useful evaluation criteria for both acceptance and maintenance VLF-tests.