VLF hipot and VLF testing is as simple as an AC hipot on lower frequency output (at 0.1 Hz). The only way to field test high capacitance loads with AC voltage, like cables and motors/generators, is to use a VLF AC hipot. Lower the frequency, Lower will be the current and power needed to test high capacitive loads. The reason it has not been widely used for more than 4-5 years is because only in the last 5 –10 years has it been determined that DC voltage testing damages solid dielectric cable and is an ineffective means of determining insulation quality. The IEEE/EPRI/CEA and other world engineering bodies recommended VLF test level for solid dielectric cable is up to three times (3Vo) line to ground voltage for 15 + minutes. For example, A 15 kV cable system, with line to ground voltage up to 7.2kV, is to be performed at 22kV. VLF hipot testing is not destructive for good insulation and does not lead to premature failures unlike DC voltage testing. Using VLF does not cause degradation of the insulation. However, it is not a diagnostic test; it is an AC stress test. A cable either holds the test voltage or fails. If a cable can’t hold 2 – 3 times normal voltage, it’s not going to last long. That is actually the main intent of the test to find the fault and make it repair and be left with the good cable. VLF Hipot testing kit supplier in India VLF hipot testing kit supplier in Mumbai VLF hipot testing kit supplier in Maharashtra