Hi-pot Testing of Cables

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Rick Christopherson

Rick Christopherson

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I have a power distribution tester that I designed for companies that rent out portable power systems. The idea behind it is that the power cables and distribution panels get modified in the field, and there is no simple and quick way to know if miswiring conditions exist. (If you are curious, here is a description: http://www.rts-engineering.com/)




I originally designed this for companies in the rental business, but recently I have had several cable and panel manufacturers interested in testing all of their products before they leave the factory. This new category of buyer wants my tester to also perform hi-pot testing too. The problem is that I don’t know anything about hi-pot testing, and I was hoping someone here could educate me a little bit.
  • Given that the tester operates on anything from a 3-wire to 5-wire system, how would a cable be tested? My guess is that I would connect the HV lead to one conductor at a time, and ground all of the remaining conductors. Is that correct?
  • Does the tester need to connect to both ends of the cable, or just one?
  • Is there any type of specification document (ISO, UL, etc.) that dictates how a test is performed on cables, such as voltage, duration, method, etc.?
  • Does anyone have any sources for a no-bells and whistles tester that I can build into my PLC-based tester and communicate with it?
If it gives you a better idea of what this is, here is a picture of the previous model.
R5-sm-lo.jpg
 
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If I might be so bold as to expose my ignorance yet again, which I do so often (in with such florish!), is hi-pot testing the same as meggering?
 
George Stolz said:
If I might be so bold as to expose my ignorance yet again, which I do so often (in with such florish!), is hi-pot testing the same as meggering?
Click to expand...

They are both overpotential tests but different equipment, procedures and purposes. The differences have been discussed at length here before.

Looks like this is application is for LV cables, you dont hipot LV cables, I think the OP really is asking about Insulation Resistance testing.
 
I have been doing some digging into this, including calling Megger, and contrary to some of the previous discussions, the difference between a hi-pot and Megger is not correctly stated.

As was previously mentioned, Megger is just a brand name for the same types of test instruments, including hi-pot testers. I think the confusion is that most people associate Megger with an "Insulation Resistance" test, as opposed to the "Dielectric Withstand" test. The two tests are similar, but the units are different. Most of the testers I have researched perform both types of tests with the same tester (Megger does both, but not with the same product).

In my case, the voltages would be similar for either test, and range from 1000-2000 volts, for fairly short periods.

There are still a few more things that I am going to have to learn, such as what specific Standards should the tester follow, but so far, most testers have enough flexibility that I don't need to know this until I begin the actual design and re-programming of my PLC.

Because I need to test 3, 4, and 5-wire cables, I need to determine which would be more cost effective: a multi-channel scanning tester, or the additional internal relays in my own tester to scan the test across each conductor while using a simple single-channel tester.

The testers from Slaughter and its sister company Associated Research have very simple relay I/O for PLC control which makes my programming super simple, but limits the test data to simple pass/fail results.

I still would like to find a dirt-cheap tester that doesn't waste a lot of cost on the user interface, but instead relies on external communications, specifically with PLCs.
 
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