... for testing power cables, transformers, switchgear, rotating machinery and other Very Low Frequency Tester for High Voltage Cable VLF-40KVProduct DescriptionAC ... cables and electrical apparatus is now easier than ever!VLF (Very Low Frequency) Testers are suitable for testing power cables, ... were to be proof tested at 50/60 Hz, it would take a very high power, huge, heavy and expensive testers and ...