Does Partial Discharge Test Make Hi-Pot Unneccesary? 7

[FEinTX]

Hello,

We are building a wind farm with a 34.5 KV collection system. The contract calls for hi-pot testing prior to energization of all circuits. In addition to the hi-pot, the customer has recently decided to have the entire collection system tested by a reputable firm using Partial Discharge equipment/analysis.

Question (1): Is there any added value to doing the hi-pot test, or would this now be unnecessary?

I've been told that a PD test will catch everything that a hi-pot will, and more, but need to be sure before deciding to skip the hi-pot.

Question (2): Are there any potential risks to doing a 1.5X hi-pot test on brand-new cable?

I am aware that hi-potting can lead to premature failure on cable with early-stage water penetration, but I'm not sure if there are risks if the cable is newly laid.

Thanks for any clarification you can offer!

FEinTX

 

[benlanz]

Zogzog,

I believe I understand your question much better now. Your question is a good one. No test can predict if a cable is going to be mistreated and over heated. However, some conduction types of defects can produce localized heating. This is a very low probability event in extruded insulation (plastic and rubber) but, there is a substantial probability in paper insulation. With the data I have seen, I would say that the chance of detecting conduction defects with a DC test in extruded cable systems (such as the systems at wind farms) is less than 1%.



Benjamin Lanz
Vice Chair of IEEE 400
Sr. Application Engineer
IMCORP- Power Cable Reliability Consultants