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Old 03-17-2017, 10:08 PM   #1
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Default MV cable shield

Does 4160v cable usually have a shield? Looking at a feeder that failed last week for unknown reasons (still investigating) and it only had a ground wire - no shield. Is this common? It was a TECK90 cable by Southwire - the stuff with the orange jacket.

http://www.southwire.com/ProductCata...rodcatsheetT37

Anyhow, cable was in a conduit and it blew the fuses. Phase-to-phase fault. Keep you updated when we find out more, but more than likely shielding would have saved it.

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Old 03-17-2017, 10:29 PM   #2
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Most of the 5 kv teck cable I've done is unshielded.. It has been in both the orange and black jackets... And the SOW I've used is also unshielded.. I think I'e only worked on few couple of shielded 5 kv cables..
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Old 03-18-2017, 12:15 AM   #3
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In my experience, 5KV cables (more than 1 conductor) are not shielded. Single conductor wire usually is shielded. If there's no neutral, the shield is the ground. If there is a neutral, it's the shield and a separate ground is pulled.

One exception is airport lighting wire (single conductor, 5KV) is not shielded.

Higher than 5KV, everything is shielded except the ground. It's basic 600 volt wire.
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Old 03-18-2017, 10:54 PM   #4
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Sorry for delay on my reply on this one.,,


Most case I useally run into most of the MV cables useally unshielded but for single run of conductor it will be shielded ( pay attetion to bonding on shield part )

There is not too much differnce between the unshielded and shielded verison.

I useally run into alot of MV DLC ( diesel locomovite cable ) in my area.
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Old 03-21-2017, 01:31 AM   #5
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Originally Posted by micromind View Post
In my experience, 5KV cables (more than 1 conductor) are not shielded. Single conductor wire usually is shielded. If there's no neutral, the shield is the ground. If there is a neutral, it's the shield and a separate ground is pulled.

One exception is airport lighting wire (single conductor, 5KV) is not shielded.

Higher than 5KV, everything is shielded except the ground. It's basic 600 volt wire.
Found the problem. Cause of failure is still questionable, but most likely installation damage at this point.

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Old 03-21-2017, 01:01 PM   #6
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I'm not sure if this is one of those minor differences in the NEC vs the CEC, but the NEC here made shielding mandatory for field wiring over 2kV some time ago. The only place you can use unshielded cable in inside of gear, and in "industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation", or where replacing existing MV unshielded cables (because it USED to be OK, so those installations are "grandfathered". There are other exceptions as per usual of course.
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Old 03-21-2017, 10:19 PM   #7
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Found the problem. Cause of failure is still questionable, but most likely installation damage at this point.

That looks icky........lol.

An in-line splice on MV TEK cable is not much fun and it takes a long time. And your arms and hands will be sore for a while.........
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Old 03-22-2017, 01:01 AM   #8
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That looks icky........lol.

An in-line splice on MV TEK cable is not much fun and it takes a long time. And your arms and hands will be sore for a while.........
Not too familiar with the logistics of a TECK splice, but it was pulled through a buried conduit, so a splice was probably less than economical in this case. Fault was somewhere in the middle of the run. Paid the $40k and pulled a new feeder.
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Old 03-22-2017, 01:06 AM   #9
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Quote:
Originally Posted by JRaef View Post
I'm not sure if this is one of those minor differences in the NEC vs the CEC, but the NEC here made shielding mandatory for field wiring over 2kV some time ago. The only place you can use unshielded cable in inside of gear, and in "industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation", or where replacing existing MV unshielded cables (because it USED to be OK, so those installations are "grandfathered". There are other exceptions as per usual of course.
Why did they make it mandatory? Was it because the shield might make the cable less likely to fault given external influence (metal, water, dirt, etc)? I couldn't imagine what it would be like to terminate a shielded 4160v cable into a peckerhead of a motor...that is unless they make them much larger these days.
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Old 03-22-2017, 01:12 AM   #10
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Quote:
Originally Posted by triden View Post
Not too familiar with the logistics of a TECK splice, but it was pulled through a buried conduit, so a splice was probably less than economical in this case. Fault was somewhere in the middle of the run. Paid the $40k and pulled a new feeder.
Ouch!
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