ohmhead
Senior Member
- Location
- ORLANDO FLA
General old cable question 5kv 500 mcm 8 years old testing cable ?
Most effective way safe way ?
We had a track hoe hit a cable blow out 4160 v cable is 750 feet long .
To repair this a splice in a manhole was made one end replaced new and old end remained thur a manhole to the MDP switch to save cost requested by owner .
The old cable end was tested with a meg test showed good meaning the old part of that run left in it was asked by engineer not to hi pot this old cable due its age .
The new cable now spliced was high potted before splice was made tested good .
When we turned on MDP sw we had voltage issues the transformer it was feeding was a step down trans 4160 v to 480 v 3 phase its secondary output was 435v p/p and went down under load p/p 160 volts we shut her down fast .
Took off ABC terminations at MDP SW took ohm meter to each phase there was a dead short to its ground foil ground inside cable one[ A ]phase cable .
So the megger did not detect this before hand but the engineer would not let us use the hi pot .
Now would a VLF test been better to use or a discharge test your answer please ?
What would have been the most effective way i wanted to replace the entire run but was stopped by others .
Now there wishing it was done the fuses in MDP did not trip out but the shield inside cable is shorted to the core why or how can this be not effecting the trip .
ZOG were are you !
Most effective way safe way ?
We had a track hoe hit a cable blow out 4160 v cable is 750 feet long .
To repair this a splice in a manhole was made one end replaced new and old end remained thur a manhole to the MDP switch to save cost requested by owner .
The old cable end was tested with a meg test showed good meaning the old part of that run left in it was asked by engineer not to hi pot this old cable due its age .
The new cable now spliced was high potted before splice was made tested good .
When we turned on MDP sw we had voltage issues the transformer it was feeding was a step down trans 4160 v to 480 v 3 phase its secondary output was 435v p/p and went down under load p/p 160 volts we shut her down fast .
Took off ABC terminations at MDP SW took ohm meter to each phase there was a dead short to its ground foil ground inside cable one[ A ]phase cable .
So the megger did not detect this before hand but the engineer would not let us use the hi pot .
Now would a VLF test been better to use or a discharge test your answer please ?
What would have been the most effective way i wanted to replace the entire run but was stopped by others .
Now there wishing it was done the fuses in MDP did not trip out but the shield inside cable is shorted to the core why or how can this be not effecting the trip .
ZOG were are you !
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