Hot SWA gland

[HEARDY]

I have a hot SWA Gland on a 11kV cable. The cable has a SWA Gland on each end. I was under the belief that this would create a current circuit. There is 3 trefols running in parallel.

Any suggestions

 

[R-fur]

A gland should not get hot. If you have trefoils they should be glanded in to a non- ferrous gland plate to minimise eddy currents. I suspect that this has not been done and the heat you are feeling is actually coming from the steel gland plate.

 

[davesparks]

Trefoil cables should be glanded to a non-ferrous gland plate, or have a slot cut linking each hole. Also the glands and locknuts should be non ferrous if using the slot method.

I believe they should also be bonded to earth at only one end to avoid circulating currents, but I'm not 100% certain

 

[StephenRowley]

Could be induced/circulating have seen issues with 400kv GIS stuff but not got any experience with 11kv.

As it's HV stuff it really needs looking at by someone who really know there stuff. Earthing on HV gear is real dark art.

 

[R-fur]

Circulating sheath currents depend on the load and the circuit length. For short lengths of a few meters it is normal to earth at both ends, for a few tens of meters, earth at one end only. Longer lengths are earthed at one end and have sheath voltage limiter at the other end (SVLs are metrosils connected between the sheath and local earth). Longer lengths of a few kilometres often have link boxes where the sheaths are transposed between phases.
This is all rule of thumb stuff, it should be properly designed as StephenRowley said.

 

[HEARDY]

A gland should not get hot. If you have trefoils they should be glanded in to a non- ferrous gland plate to minimise eddy currents. I suspect that this has not been done and the heat you are feeling is actually coming from the steel gland plate.

Cheers. I'll check that out. But I thought smarter people than me would have picked that out in construction.

 

[westward10]

I suspect they are connected through a non ferrous plate, it would be school boy error not to and the issue is not likely to be evident at one gland. It could be down to a poorly fitted or loose gland.

 

[HEARDY]

I suspect they are connected through a non ferrous plate, it would be school boy error not to and the issue is not likely to be evident at one gland. It could be down to a poorly fitted or loose gland.

Yep. Just confirmed a Brass plate. Also can confirm it is a Ali Wire Armour not steel as first thought.
We are working on incorrect fitting but have t o wait for some isolations to drop the bottom of the gland to inspect.
We are getting arcs between glands if we bridge the gap a little.
Still think this AWA cable shouldn't be earned at both ends.

 

[westward10]

It is almost certainly not fitted correctly and the circulating currents are causing it to get hot.

 

[Andy-1960]

I would be interested to see a photo of this and the type of cable being used.
What sort of current is being drawn to warrant 11Kv cables to be installed in parallel, I have never seen this done.
Are you sure they are in parallel and not part of a ring or a tee’d radial feed?
I have my doubts about it being circulating currents, I think it may be the AWA being used as an earth path.

 

[davesparks]

I would be interested to see a photo of this and the type of cable being used.
What sort of current is being drawn to warrant 11Kv cables to be installed in parallel, I have never seen this done.
Are you sure they are in parallel and not part of a ring or a tee’d radial feed?
I have my doubts about it being circulating currents, I think it may be the AWA being used as an earth path.

Nobody has said they are installed in parallel, as far as we know it is just three single core cables in a trefoil arrangement.

 

[HEARDY]

Nobody has said they are installed in parallel, as far as we know it is just three single core cables in a trefoil arrangement.

there is 3 sets if single core 300mm 11kv cable between switch and terminal box. Photos attached.
[automerge]1582371824[/automerge]

I would be interested to see a photo of this and the type of cable being used.
What sort of current is being drawn to warrant 11Kv cables to be installed in parallel, I have never seen this done.
Are you sure they are in parallel and not part of a ring or a tee’d radial feed?
I have my doubts about it being circulating currents, I think it may be the AWA being used as an earth path.

Photos attached

 

[R-fur]

Looks like a tidy install, What length are the cables, what is the load?

 

[Andy-1960]

Why do people find it so hard to read a post properly and instead seem to take a guess at what has been written?

The OP clearly states:

There is 3 trefols running in parallel

 

[HEARDY]

Looks like a tidy install, What length are the cables, what is the load?

It's around 150mtr but not sure on the load. The cables are over spec. Only operating at less than 6000 volts