T&D World Magazine

Instrument Combines VLF AC Hipot, Capacitor Discharge Unit

DC testing of solid dielectric cable is largely ineffective, highly discouraged, and discontinued by most. The preferred method is to use AC voltage to test cables, and for long cable runs, a Very Low Frequency (VLF) AC hipot is required. A VLF test is a pass/fail stress test and if a cable or splice defect cannot hold the test voltage, it will fail. The fault must be located and repaired, requiring the use of a capacitor discharge unit (thumper) and possibly radar. High Voltage, Inc. combines the VLF, thumper, and radar capability all into one package.

For simplified fault locating, the VT30 can be combined with the TDR-20 radar unit. The TDR-20 drastically reduces fault locating times and stresses imposed on the cable during thumping. The internal arc reflection filter is compatible with other radar units on the market and allows for future upgrades.


  • Single piece combination VLF hipot/burner and capacitor discharge unit
  • Repetition rate of eight seconds
  • Internal arc reflection filter
  • Simplified controls for minimal operator training
  • Zero start high-voltage interlock
  • Single pulse or continuous discharge mode
  • Side-mounted storage reel to hold cables and accessories
  • Output vise clamps for assured contact to test cable and ground
  • Operation from either line, generator or inverter
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