Using a Hi-Pot tester in place of a Megger-Deciphering Readings

I have a hi-pot tester, and need to test the insulation on some cables that are used on 230 Volts to see if they are safe to use. The tester is able to use lower voltages like a megger.

On the tester, it measures the current leakage in micro-amps. In playing around with it, testing conductors, applying 1KV for about a minute results in about 2 microamps draw being shown on the meter. The current starts dropping ever so slightly towards the end of the minute period. On another conductor, the scale barely moves off zero amps.

How does one use the hi-pot tester to determine insulation condition? Is there a chart that shows acceptable amount of current leakage in relation to applied voltage? Or do I need to look at the current draw stopping/dropping instead of increasing as a determination that the insulation is in good condition?

There are DC and AC Hi-Pot testers. Both work, both are allowed for most actual Hi-Pot tests, but the results are different.

The DC tester can determine the actual resistance. With 2 microamps and 1000V, if the tester was a DC type, you would seem to have about 500 megohms resistance, a number that equals good insulation in virtually any normal equipment.

Are you sure it was microamps?

The AC type tester measures the combination of DC resistance and capacitive leakage. You do not get a resistance, but you can verify total leakage current, which is also good as a test.

Normally, the leakage currents are measured in milliamps for purposes of determining too much vs OK, which is why I asked the question about being sure of the units being microamps. GFCI devices are rated to allow only 3 to 5 milliamps of ground current (same as leakage in most cases). Same for "touch currents" and other names for leakage current, small numbers of milliamps.

A capacitance passing milliamps at normal AC voltages will pass more at higher voltage, which is why DC is often used, to differentiate AC leakage from actual resistance leakage through bad insulation. DC testers may indeed measure microamps.

Thanks, great information! Its a Biddle DC test set I'm using. Its also micro amps on the scale I'm using, its the lowest value on the selector knob for the amps scale, labeled μA. The higher scale selections on the knob go up to 5mA.

Thanks again for your help!