With cable diagnostic testing becoming more common, the need for fault locating will rise. If a cable cannot withstand the test voltage, failure will occur, requiring fault locating. If you're in the market for a thumper, why not get one with a VLF hipot built-in to test the AC integrity of the cable following repair. The VT33 incorporates a powerful VLF hipot, a VLF Burner that rapidly reduces a faults impedance (arc-over voltage), TDR/radar capability, and continuous discharge for pinpointing the fault. Suitable for cables up to 25 kV. HVI puts all the tools needed in one box.