DC Hipot test voltages for new cable

[rdvette]

I am required to do a hipot acceptance test of newly installed 15KV EPR copper cable. I have heard that a standard rule would be to Hipot at 3 times the rated cable voltage or 45KV DC. Is this a good rule to follow?

 

[dapotiti18]

rdvette, i want you to understand that hipo test is use to ascertain that insulation level between phase to phase conductor or phase conductor to earth.so therefore same thumb rule that is applicable to insulation resistance test is applicable for this test.This thumb rule state that if you inject a 1kv to equipment confirm insulation resistance but the minimum acceptable is 1meggerohm.for 15kv cable the injected voltage should not be more than 2x15kv is equal to 30kv becuase a voltage higher than this can rapture the cable. so the minimum resistance for this test is 30meggerohm.therefore minimum leakage current this test is 30kv divided by 30meggerohm is equal to 1mA.

 

[jghrist]

Will using a thumper to locate a fault damage the cable in other locations? Seems like the same mechanism that can damage aged cables with a dc hipot would apply when using a thumper.

 

[dpmac]

jghrist,

I always enjoy asking asking the VLF Hipot sales rep that question after a half hour "DC is bad lecture".

One VLF hipot mfg did produce a small (low joule) VLF thumper for a year or two. It simply charged + DC and thumped then charged - DC and thumped.

In reality the thumper voltages and duration in which it is actually applied are certainly less then the DC maintenance test voltages that began the "DC Bad" movement in the first place.