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Why Engineers Prefer VLF Hipot Testing

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A VLF hipot or very low frequency is a test done to detect defects on electric cables. This is to test if the insulator can withstand the operating voltage and not breakdown. It is not a diagnostic test but rather a stress test. It is similar to an AC hipot test but the test voltage is at 0.1 hertz. 

In earlier days, an AC hipot test required a large amount of power to energize a cable. This is because of the low capacitive reactance. A cable can act as a capacitor because of the conductors and the insulator acts as the dielectric. With VLF hipot test, it takes 600 times less power to power the cable. 

Some of the advantages of VLF testing are:

  • lesser voltage transients during the test
  • not prone to flash overs
  • doesn’t generate harmful voids in the insulation because of treeing
  • space charges are not injected into the dielectric and it doesn’t generate traveling waves during the test
  • The test equipment used in this test is also smaller and lighter compared to other tests, making it convenient for engineers to test devices

Protec has a wide array of test equipment for rent or purchase that are perfect for preventive maintenance or electrical emergencies.