Rob, you say short runs seldum cause problems. Well, one the the guys here is your age and well experianced, he put a scenario out for the boys one day to see who could get it. I'm not sure this is up your alley, but give it a go. I was the only one who got it but I'm a bit older than the others and knew straight out and didn't have to think.
Problem- Sub-station supplies a main board at a large complex. It has three sets of 240mm2 SDI's per phase run in parallel. The run is only 11m long and the cables are run flat on cable tray. The cables were running very hot so thermal imaging was taken. There was no hot spot at fixing point as thought but the entire cables were red hot. Why?
What is the MDI indicator saying?
What is ambient temperature of the environment.
Were the SDIs run as four groups. Ie red (3xsdi) white (3xsdi) blue (3xsdi) red neutral (3xsdi)
If they are laid out in some side by side layout or worse still random layout then there could be electric field heating effects.
Then of course it could just be heat concentrating if they are jammed against each.
If I did the job I'd layout them on the tray
R
R
R
S
S
S
T
T
T
N
N
N
In horizontal layout.
Was the tray earthed?
I'll read some books about electric fields and get back.
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