So a crew went out tested a General Cable 35Kv White EPR cable, the highest rating they got on insulation resistance 5KV for 1 min was 75,000 megohms… Passed Tan Delta and 60Min VLF withstand, but the engineer is now kicking back the report saying it failed on insulation resistance based on the Neta 100.1. Has any one had an issue like this come up and how did you deal with it.
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I would show the engineer table 100.1.
- For cables, the acceptability for energization should not be determined by the recommended minimum insulation resistance values shown above. Conductor and insulation geometry, temperature, and overall cable length need to be taken into account per manufacturer’s published data for definitive minimum insulation resistance criteria.
It’s not black and white.
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Based on the 75k value, I’m assuming you used a separate insulation resistance tester and didn’t use the VLF to perform the DC test. Those results are typically lower than a Megger insulation tester. Figured I’d mention something anyway.
Also, what is the length of the cable? Capacitance plays a major role in the value. Its not uncommon to get values less than 100k megohms. 100k is a recommended value. But you could always point them back to the code book and state that you only need 36 megohms to energize the cable.
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The length is roughly 365 feet I didn’t have the TDR with me to get an accurate measurement. The engineering group on this project seem to be looking for a gotcha and I think there trying everything they can to hold up the contractor that hired us to test. Ive had 10 meetings explaining results vlf and tan delta differences etc. so this was there last hang up. We ended up going back to test the cable again and did get above 100 gig’s.
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