Outdoor Tx. Cabling Problem (Pictures)

[ghostbuster]

Here is the problem:

We found the answer to this problem,but I thought it may be of interest to share with the group.

Hint:All connections are tight, it is simply a cable arrangement problem

 

[iwire]

The support cross bars are ferrous and separate each phase.

 

[bob]

Ghostbuster
Could you provide more detail

 

[ghostbuster]

Ghostbuster
Could you provide more detail

Bob

Here are a few more pictures you can chew on:

 

[ron]

As Bob inferred, I would also guess inductive heating from isolated phases.

 

[steve66]

I also agree with Ron & Bob.

It looks like cables from one phase drop on one side of the glowing I beam, and cables from another phase drop on the other side.

Or, there is at least one cable dropped on the wrong side of the Ibeam.

 

[JayP]

I'm thinking beam clamps have something to do with poor ground /neutral connection causing heating...

 

[big john]

The numbers in the pictures, are those relative temps. or actuall temperatures? C or F? Wondering how hot this actually got?

-John

 

[ghostbuster]

The numbers in the pictures, are those relative temps. or actuall temperatures? C or F? Wondering how hot this actually got?

-John

The temp. in the pictures is in actual Celcius.
28c is 82f

100c is 212f

 

[ghostbuster]

The support cross bars are ferrous and separate each phase.

Bob

Can you explain to the group,why only these outside support bars heat up.The same type of support bars going into the plant are not heating up.

 

[JayP]

negative sequence/circulating currents?

 

[gar]

091030-1326 EST

If your color photo was a real visible spectrum image, then you would get this kind of result:

Try this chart to judge the temperature:
http://www.smex.net.au/Reference/SteelColours.htm
Looks in the range of 1500 to 2000 deg F.

Therefore, the picture is IR with some synthesized colors.

How much power is dissipated in that beam for a rise of about 40 deg C? Probably several KW.

.

 

[ghostbuster]

Here is the answer (Iwire was pretty warm):

The heating is caused by stray magnetic fields flowing through this ferrous(magnetic) support beam.
The zero sequence current (and corresponding generated magnetic field ) is very high near the end of the busduct(only neutral conductors).
As you move closer to the building , phase a.b.&c conductors are connected to this busduct and the zero sequence current decreases proportionally(and also this radiated net magnetic field decreases as well).
Therefore these steel support bars were not heating up near the building.
Using non-ferrous supports would essentially block the magnetic field flow and this heat build-up.