Medium Voltage splice meg test

[Pok3r]

Hello guys, at my work one of the subcontractor damage a MV cable, I have done a lot of MV terminations on lots of different transformers but its the first time doing a MV splice which it so what similar. The splice its done and am very confident on my work, I use the Fluke 155c at 5000v for 5 minutes disconnecting a the transformer, the results were A 13.2 G ohms, B 76 G ohms and C 120 G ohms. Phase A was steady going up really slow to 13.2 G ohms. The splice was un detected to know which phase it was done because it was direct burial and only one cable was showing up.

My concern is that from my understanding a steady reading could mean that there might be a weak insulation not necessary a damage cable. Does any one have a good understanding on what could be the cause of this results? And Also can someone clarify for me if it is same to energized/close a MV disconnect under load?


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[Sahib]

There may be water absorption by insulation of phases to different levels. A heat run test of the cable may confirm it.

 

[GoldDigger]

There may be water absorption by insulation of phases to different levels. A heat run test of the cable may confirm it.

Perhaps moisture entered the damaged section of cable before the splice was completed?

 

[Tony S]

Was the splice done as a repair or as a normal cable extension? For a repair I’ve always chopped out 20Ft and done a splice either side of the fault to ensure there has been no carbon tracking. For extending the cable then damp is the likely culprit.

 

[Pok3r]

Was not aware of that distance, the splice was a repair. But the meg test was 15.0 G ohms on a 5000v for 5 minutes. What can you say about that.


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[Sahib]

Was not aware of that distance, the splice was a repair. But the meg test was 15.0 G ohms on a 5000v for 5 minutes. What can you say about that.


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With your Fluke meter conduct dielectric absorption ratio test. Calculate polarisation index to check insulation condition.

 

[Sahib]

Perhaps moisture entered the damaged section of cable before the splice was completed?

May be especially if it is paper insulatief cable.