megger or DWT or HIpot

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unsaint34

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I am a newbie taking a cable splicing class. Lots of information to learn! I learned de-energized cables can retain capacitive charge when they were exposed to electrical field. Makes sense. But I never done megger or DWT (dielectric withstand test). I heard the testing (or hipot testing) can be used to drain the capacitive charge. Is that because the testing equipment has means to clear their test voltage, so that also clears the capacitive charge as well? Thanks
 

Hv&Lv

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Engineer/Technician
I am a newbie taking a cable splicing class. Lots of information to learn! I learned de-energized cables can retain capacitive charge when they were exposed to electrical field. Makes sense. But I never done megger or DWT (dielectric withstand test). I heard the testing (or hipot testing) can be used to drain the capacitive charge. Is that because the testing equipment has means to clear their test voltage, so that also clears the capacitive charge as well? Thanks

When are they telling you to test, and what kind of tests? Are they type 1 or type 2 tests? The only tests I have seen in the last few years was on the JCN cable, and it was to test for water infiltration only.
 

SG-1

Senior Member
The dielectric test or Hipot reduces the test voltage between the cables & ground slowly to zero. The capacitive charge reduces to zero at the same time. If the voltage is removed suddenly, say the operators finger slips of the interlock & the test set shuts down, there is likely to be a residual, capacitive charge remaining. The key is to lower the test voltage slowly.

It is always best to ground the cables, then no hazard can be present.
 

zog

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Charlotte, NC
I am a newbie taking a cable splicing class. Lots of information to learn! I learned de-energized cables can retain capacitive charge when they were exposed to electrical field. Makes sense. But I never done megger or DWT (dielectric withstand test). I heard the testing (or hipot testing) can be used to drain the capacitive charge. Is that because the testing equipment has means to clear their test voltage, so that also clears the capacitive charge as well? Thanks

I hope they are not training you to do DC hipot tests on MV cables
 
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