Dielectric breakdown dependence on amount of current

Thread Starter

sewardf

Joined Jul 21, 2007
2
In my industry we megger circuits to determine the integrity of the insulation. It is common to megger at 1000 VDC to ground. Current output of the megger is limited to less than 2 mA. The higher we raise the megger voltage the more leakage to ground occurs and new paths to ground are opened up. At the low currents used ,< 2 mA, does the opening of new paths at higher DC voltages result in insulation breakdown which then will result in more leakage at the lower normal circuit operating voltages? To rephrase the question are the low leakage currents present during testing sufficient to cause any permanent reduction in the capability of the insulation at the lower operating voltages?
 

bloguetronica

Joined Apr 27, 2007
1,359
In my industry we megger circuits to determine the integrity of the insulation. It is common to megger at 1000 VDC to ground. Current output of the megger is limited to less than 2 mA. The higher we raise the megger voltage the more leakage to ground occurs and new paths to ground are opened up. At the low currents used ,< 2 mA, does the opening of new paths at higher DC voltages result in insulation breakdown which then will result in more leakage at the lower normal circuit operating voltages? To rephrase the question are the low leakage currents present during testing sufficient to cause any permanent reduction in the capability of the insulation at the lower operating voltages?
I think not, unless we are talking about electrolytic caps. As long as the current is limited so the breakdown won't cause excessive heat, it is safe.
 
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