Single Core cables and Steel Gland Plates
Single Core cables and Steel Gland Plates
(OP)
I have an applications where I'm installing 3 single core XLPE/AWA Cables.
The cables will be installed into an existing Steel Gland Plate and I need to calculate the possible circulating currents in the plate. (I know it should be a non-ferrous but it;s not really an option.
Does anyone know how to do this?
I know cutting slots in the gland plate will reduce the circulating current, but where do I cut the slots?
Is it two slots, across the width of the gland plate between the Cables.
Or
One slot across the length of the gland plate through the middle of the holes in the gland plates.
The cables will be installed into an existing Steel Gland Plate and I need to calculate the possible circulating currents in the plate. (I know it should be a non-ferrous but it;s not really an option.
Does anyone know how to do this?
I know cutting slots in the gland plate will reduce the circulating current, but where do I cut the slots?
Is it two slots, across the width of the gland plate between the Cables.
Or
One slot across the length of the gland plate through the middle of the holes in the gland plates.






RE: Single Core cables and Steel Gland Plates
The eddy currents can be calculated using the CSA of the conductor, distance to the plate, materials, air gap in gland, primary (circuit) current etc. The calculation isn't very complex, but I'm not sure the answer will tell you very much.
The traditional solution as you rightly point out(other than another gland plate) is to cut slots between the glands. i.e. if you have three glands the first cut goes between the gland 1 and gland 2, the second cut goes between gland 2 and gland 3.
It tends to weaken the plate, so you can make the cut but leave a small piece of steep uncut in the centre of the line. The other thing to consider is the ingress of moisture and duct. some sort of insulating material along the inside of the plate usually works.
Hope this helps.
RE: Single Core cables and Steel Gland Plates
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Single Core cables and Steel Gland Plates
eti,I was hoping to be able to figure out what the heating effect due to eddy currents would be. Before I make cuts in the gland plate I would like to be sure that it is necessary.
Should the Cables enter the Gland in Trefoil? Would that cause much of a reduction in eddy currents?
RE: Single Core cables and Steel Gland Plates
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If we learn from our mistakes I'm getting a great education!
RE: Single Core cables and Steel Gland Plates
Before you put cuts in the gland plate make sure there is no internal arc requirement, putting slots in the gland plate might invalidate internal arc protection.
desertfox
RE: Single Core cables and Steel Gland Plates
Regards
Marmite
RE: Single Core cables and Steel Gland Plates
An aluminium plate could put onto the switchgear but it would be difficult.
I was hoping to find a way to calculate the heating due to eddy currents and see if for a steel plate the heating would be excessive.
My question about bringing the cables in in trefoil wither in a single gland, or with three bras glands arranged in a trefoil arrangement as close together as possible, is would that significantly reduce the heating effect?
RE: Single Core cables and Steel Gland Plates
What voltage is this installation? Your cable box is quite small. If it is compound filled now, then you might not have enough clearance to do a dry termination without using a cold pouring compound such as guruflex. That would rule out cutting the gland plate.
Regards
Marmite
RE: Single Core cables and Steel Gland Plates
The cable box isn't filled, just air.
RE: Single Core cables and Steel Gland Plates
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If we learn from our mistakes I'm getting a great education!
RE: Single Core cables and Steel Gland Plates
I agree, and I'll be on site tomorrow to have a good look at it. If a non ferrous gland plate needs to and can go in then it will.
But it brings me back to my key question, how do I calculate the heating that will be seen for a given gland plate.
While I don;t doubt for a second that a steel gland plate will see greater circulating currents and heating than an aluminium/brass one, I like to be able to quantify things out.
How can I prove that the steel will heat up, and by how much?
RE: Single Core cables and Steel Gland Plates
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Single Core cables and Steel Gland Plates
The best way is to replace the gland plate by an aluminum or non magnetic stain less steel plate( 306 or 316).In case you make slots,the correct way is as explained by eti.But how can you allow an open slot that may affect the integrity of the cable box. One way is make a slot of atleast 50 mm wide and then fill it by welding a stain less steel strip of same width.
RE: Single Core cables and Steel Gland Plates
I'm on vacation and can't check the current code wording.
Bill
--------------------
"Why not the best?"
Jimmy Carter