Hipot Testing Safety

[cjhut]

My corporate safety manager called me yesterday asking me a bunch of questions concerning hipot testing. Our company builds the towers for wind turbine generators. We supply the bus from the top down to the bottom and have to prove the insulation passes before they hook up the generator. I have never used a hipot before, but I do understand what the machine is used for. I will not be doing any of the work, nor do I know all of the details, but what I am looking for is some suggested safe work practices when using a hipot. I was told that we will be using test voltages of 500V and 2500V. Obviously electrically rated gloves will be needed. We also discussed roping off the area while testing. His worry was about electrically rated boots. Could we use an electrically rated matt to stand on? I also heard that the hipot's frame itself could become energized. So if we set it up on a work table, could we use a rbber matt again? I'm sure some of you medium voltage motor guys use these all the time. I would just like to know what kind of personel protective equipment you use, and how you set up your work area.

Thanks in advance.

 

[pwrengrds]

This is more of a megger test than a hipot. I would have all ends secured by red flagging or personal standing by as a physical guard. I would not be worried about shoes, but would be sure to ground it after the test using a grounding stick. A lot of the safety concerns depends on the environment that you are in and the length of the test.

 

[Zogzog]

You need to treat it the same as you would an energized conductor at that voltage, I sent an letter to OSHA on this a few years back and recieved a letter of interpretation. In addition to your gloves and other shock protection you will also want to have a means to discharge the stored energy. The hipot has a ground on it that needs to be connected toa good grounding point.

I agree with everthing pwrengrds posted too.

 

[electricpete]

Some tidbits:

Do a live/dead/live test to confirm equipment deenergized if applicable. In our plant it is applicable most of the time.

The winding holds charge after you ground it. Should ground the winding for 4x the length of time that dc voltage was applied before handling leads. Also conducting additional tests without grounding the winding for a length of time first can result in erroneous results.

The aforementioned grounding stick should have a discharge resistor in it so as not to introduce a severe transient when you contact the motor (which resembles a big capacitor)

Know your test equipment including guard and ground connections.

* Need a competent person overseeing the test.





=====================================
Eng-tips forums: The best place on the web for engineering discussions.