Lead Wires sufficient for PD testing 1

[parsonsparsons]

I have been tasked with purchasing new lead wires for our partial discharge / corona testers. I am not sure which kind I need to buy or what ratings it needs. We test power transformers in the 1-50kV range and do not exceed 100mA. Any help would be greatly appreciated, thank you.

 

[dpmac]

We use Okonite Part Number 504-22-3495 HV Cable coupled with Elastimold HV Terminations Part No. 35MSCEBBG (one per end of course).
We have found this combination to be PD Free to 60kV if properly terminated.
Cables are flexible, lightweight and long lasting if cared for.
Have used in lengths of up to 150 feet long so far.

Info can be found here:

http://www.okonite.com/product_catalog/section6/sheet1.html

Hope this helps.

Pat

 

[ausphil]

It depends on whether the lead is to be self insulated (as dpmac has given the example of), or if you are hanging them in the air from your test transformer to your equipment that you are testing, in which case they don't need to be insulated.

In addition to insulated leads, for voltages up to around 50 kV we use spiral cord (similar to that used between guitars and amplifiers) and put banana plugs and aligator clips on the end for easy connection. It is a cheap setup, and can be re-terminated easily onsite. The lead will be PD free up above 50 kV as it has an effective diameter of about 15mm. The same length lead can be use for long or short distances, just by wrapping the excess length around one of the terminations.

As long as you have a decent size donut around the connection at either end, the connections will also be PD free up above 50 kV.

This arrangement also has the advantage of not sucking too much current into the capacitance of the cable, although this can often offset the reactive current required when supplying a transformer.

If you are in a noisy environment, a shielded cable as suggested by dpmac would be a good option.

ausphil

 

[parsonsparsons]

Thank you for your responses so far. I'm not really knowledgeable on this subject. To follow up,

The room in which we do our PD tests is shielded. Right now the leads we are using are either polyester or teflon insulated with an additional silicone layer on top of it, so pretty decent already. We use banana plugs and alligator clips as well to connect our parts frequently.

However, testing some parts at 8kV+ with alligator clips results in noise. We have round brass ball fixtures that I use in this case to ensure the only PD I'm reading is from the part itself. The setup can be tricky however, and this is basically why I'm tasked with figuring out if we need new leads in order to avoid this "false partial discharge." Hope this helps.