VLF Test Kit

VLF Diagnostic Test Services

HVPD offer a test service for commissioning and maintenance testing of land and subsea MV cables using 60kV and 90kV Very Low Frequency (VLF) off-line HV test units with partial discharge (PD) and tan delta (TD) diagnostic test modules. HVPD test to both customer specifications and to commonly used standards such as the IEEE Standard 400.2 for VLF testing. Unlike standard VLF voltage withstand testing, our diagnostic VLF PD/TD testing provides a full condition assessment of the MV cable’s insulation condition, prior to going into service, rather than a simple pass/fail result obtained from the standard withstand test.

Test services offered

  • Time‑domain reflectometry (TDR) cable fingerprinting.
  • VLF maintenance withstand testing with diagnostics (typically at 2.0-2.5 U0).
  • VLF commissioning withstand testing with diagnostics (typically at 2.5-3.0 U0).
  • Partial Discharge (PD) and Tan Delta (TD) diagnostic testing.
  • Partial Discharge Cable Mapping (PD site location).


  • Partial Discharge testing with PD mapping shows the location of any cable defects.
  • Tan Delta testing assesses the overall quality/degradation of the bulk cable insulation.
  • Combined PD and TD diagnostic testing efficiently supports asset management decision‑making on the future service‑life of the cable and whether a newly commissioned cable is fit-for-service.
  • TDR testing identifies joint positions and pulse propagation speeds along the cable.
  • The portable 60kV and 90kV VLF test kits are suitable for both onshore and offshore use.