# Hi-Pot Vs Megger Testing



## Big John

DC hipot is doing the exact same thing as a megger: Putting direct current on the line and giving a readout of the combined charging, polarizing, and leakage current. Hipot just applies more stress, that's all.

If you were getting a solid ground with a megger you would've gotten the same with a highpot.

Wet cables will meg worse, but definitely not as a GF unless you had a significant leakage path. Put it this way, all the conductors were wet, right, but only C gave poor readings? No good.

What were your test values?


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## JW Splicer

I've never seen anyone hipot 600V cables. A megger is a megohmeter, measures insulation resistance. A hipot tester basically works the same way, but measures leakage current. If you see a fault with the megger, you will see a fault with the hipot. The hipot stresses the insulation weak points at higher voltage levels than the megger will. 

I don't think the hi pot will do anything for you except maybe create an unwanted fault/flash over. Are the motors delta? You can have a single phase ground fault on delta systems and still pack full load. with a wierd reading on C phase, I'd bet you have no ground reference. A second fault could be really bad.


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## dronai

Thanks guys, That clears that up about the Hi Pot.

I think the short from the motor ruined the breaker. That's why C phase was low.

Pump guy thought it was the other way around, the motor single phased when the breaker failed. But I think the overloads would have opened on the starter and protected the motor.
I used 1000V on the Meggar. Must have been the damp insulation, because we energized and it worked.


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## Big John

dronai said:


> ...Must have been the damp insulation, because we energized and it worked.


 That's why I was curious about the values. You could have stuff that measures in the single digits but will still operate because it hasn't completely failed even though it's in very bad condition.


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## pete87

How long is the Hi-Pot test done ? surly not long .


Basically High Potential on 600V insulation .

I smell an old timer trick ... 



Pete


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