One of most important tests on MV Cable is VLF Test. What is VLF Test..? The very low frequency (VLF) withstand cable test is essentially a type of AC hipot test conducted at a frequency rate of 0.01 to 1.00 Hz. Due to a significant drop in the operation frequency compared to AC hipot testing, done at 50 or 60 Hz, a VLF hipot tester is much smaller than a typical AC hipot test set, and thus is applicable for field usage. The advised testing time is 60 minutes at 0.1 Hz on new cables, and 30 minu