Intro

Off-Line cable testing is typically associated with commissioning but it can also be performed during routine outages and is helpful for confirming discharge locations.
In this case twelve XLPE cables were tested Off-Line for Partial Discharge during a routine shutdown.

 

Initial Assessment

The cables were energised with a High Voltage test set and the Partial Discharge level was measured with a coupling capacitor connected to the respective cable.
Eleven of the cables had a low PD reading however one Cable had a high PD reading which required further investigation.

PD and Voltage graph

PD versus Phase Graph

 

 

 

 

The Next Step…

As PD was detected on one of the cables it was important to find the location of this discharge. On-Line PD sensors and Cable Mapping were employed here and found that the discharge location was the at the crux of the cable.

Conclusions

Eleven of the Twelve Cables were in good condition and no further action was required providing peace of mind for the asset owner.
One cable had a PD issue at the cable crux which could potentially lead to failure. Knowing the exact location of this issue allows for simple monitoring and repair at a convenient time.