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Medium Voltage Cables - Onsite Testing


Cable sheath tests (dc test)

Cable sheath tests are required for new cable installations in order to ensure that cable is:

  1. continuous end to and 
  2. cable is laid as planned and 
  3. route cable joints are sound

Existing cable undergo sheath testing prior to returning to service following cable diversion or cable repair to ensure circuit integrity.

Test Description 

Test according to

  • HD     620 S1
  • IEC     60229-2007 / par.5



cable sheath test field arrangement

From the mains power dc Voltage is applied between cable sheath and earth.

Requirement of the test is that the is the cable must withstand the applied voltage (no breakdown), according to the above mentioned standards. That means that the leakage current must be less than milli ampere (sheath resistor Megohm) 




Cable insulation test (VLF test)

It is highly recommended and often mandatory to perform a VLF test on all HV cables following jointing or prolonged outages. This is done to prove the integrity of the cable prior to system energisation thus avoiding a high power failure of the cable when first connected to the system. ATE recommends and performs regular routine maintenance testing of aged cable.

Test Description

Test according to 

  • HD       620 S1
  • VDE     0276
  • IEEE     400.2




cable insullation test field arrangement

The insulation of the cable under test is subjected to a VLF (Very Low Frequency – 0.1 Hz) overvoltage test according to VDE 0276- HD 620. The conductor is completely isolated from the installation at both ends. Test voltage is applied between the conductor and the grounded metallic shield for a period of 1 hour. The insulation must withstand the applied voltage (NO BREAKDOWN must occur).


VLF 60kV test set (High Voltage Inc.)

VLF test insight wind generator