Med voltage cable grounding

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Bud1234

Member
When installing 5kv or 15kv cable should the ground in the cable be grounded on one end or both. I thinking if grounded on one end at the source it would dissipate the induced voltage. If grounded on both ends it would perform in the same manner BUT, if there is a fault, lighting or serge it would try to use the drain wire in the cable as a ground and destroy the cable. Can some one explain the corect way for installing this cable
 
When installing 5kv or 15kv cable should the ground in the cable be grounded on one end or both. I thinking if grounded on one end at the source it would dissipate the induced voltage. If grounded on both ends it would perform in the same manner BUT, if there is a fault, lighting or serge it would try to use the drain wire in the cable as a ground and destroy the cable. Can some one explain the corect way for installing this cable

Must be grounded at both ends. It has to carry the ground fault current.
 

zog

Senior Member
Location
Charlotte, NC
When installing 5kv or 15kv cable should the ground in the cable be grounded on one end or both. I thinking if grounded on one end at the source it would dissipate the induced voltage. If grounded on both ends it would perform in the same manner BUT, if there is a fault, lighting or serge it would try to use the drain wire in the cable as a ground and destroy the cable. Can some one explain the corect way for installing this cable

Both ends, that is vital to the protection system. No offense Bud but if you have to ask that I think you may want to subcontact this to a certified MV cable installer. Who is doing the testing of this cable after installation?
 

mxstar211

Member
Location
Hawaii
I have been taught wrong. Just looked it up, and it needs to be connected on both ends. The shield serves as a drain, and it also carries a portion of the fault current.
 

mxstar211

Member
Location
Hawaii
I should state my experience is in a generating yard, and I did read only connecting the shield on one end is common practice in this situation.
 

Bud1234

Member
I'm not talking about the ground conductor that is ran with the 5 kv cables. I know this has to be sized for the fault current. I speaking about the Tape shield in the cable. This is not sized to carry fault current. you can also get it with out a shield. If i remember correctly-the shield is designed to relieve the stress from the insulation. If the shield was grounded at both ends it would be in parallel with the grounding conductor. I have seen it installed bout ways. Just like to have more information on the correct way and why.
 

zog

Senior Member
Location
Charlotte, NC
We hypot every cable before energizing.

You may want to read some other threads here on DC hipot testing of mV cables. While it is still accepted by some standards for new installations only (Never DC hipot a cable in service >5 years) the effectivness of the test is limited and will only discover gross installation errors. You should be doing a TD or PD test or at the very least a VLF test.
 
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