During a hi pot testing of 11KV Al conductor, 500mm 1C, 750m long cable at 15kV, I experienced negative leakage current up to more than 10 mA. The leakage appeared at less than 2kV due to which the testing had to be stopped.

Another similar cable started giving spikes of more than 10mA negative leakage current at 5kV and continuous 10mA at 11kV.

The testing of another cable gave no more than 2 mA during the whole 1 minute that the test was carried out.

All the three cables gave less than 2mA positive leakage current.

What can be the problem with the first two cables? And how to resolve it?

 

Shamyl... did you try drying out insulation prior to testing?

Following are two Control List Topics to review:

o 1001509379 "Dielectric Testing"

o 1026230152 "IR Measurement of Cables"

Regards, Phil Corso (cepsicon[at]aol[dot]com))

 

The terminations were properly cleaned and left to dry for around 45 minutes before the test was carried out.

 

Shamyl,... What I meant by "drying-out" was, did you apply current via a low voltage source at one end of the cable, with the other end short-circuited?

Regards, Phil Corso (cepsicon[at]aol[dot]com)

 

sorry...took the phrase literally ... anyway, nothing of that sort was done!! Is the process necessary? This could be a reason of the problem...

 

Absolutely necessary. Did you read the two referenced topics?

Phil