Testing (1) set of MV cables at the same time. VLF vs Hipot

[ombligo]

Hey everyone,

So we were testing a few sets of 5 kV cables today. We had planned on testing a set all at once connecting them with a corona ball. My question was, in order to ensure all cables are getting the same test voltage, wouldn't you need to make the cables in parallel, by putting a corona ball on both ends so that the test voltage will be the same across all cables? I have asked around within my company and heard what they think but would like to hear yalls thoughts on this. I've seen some techs do it in the past do it by just tying them together at one end and putting boots on the other ends. I understand VLF and DC withstand are different since one is AC the other DC, how would tying one set of cables impact each of these tests.

I can't shake thinking of it like a circuit analysis problem. The source would be the test set, the parallel conductors the resistors. In a circuit, resistors in parallel will have the same voltage across each resistor. Still thinking this over and thinking of ways I can test my theory accurately and safely. Let me know what yall think.


Thank you

[nowwearesuckingdick]

Assuming these are shielded cables, the closed circuit in this scenario is the shield/ground as your return. The very first test you should be doing is shield continuity which verifies minimal uniform shield resistance as well as confirms phase marking at both ends. Next you do your individual DC insulation resistance tests. Finally, for the tan delta & VLF portion, you are tying all the conductors together with the corona ball at one end with the other ends isolated with the boots and then also tying all the shields together and bonding them to ground. You are applying voltage to the conductors at the corona ball and measuring your leakage current to shield/ground.