Cables in piping racks or in cable trays. Short-circuits

[radug]

Good afternoon,

A question has arisen among my workmates about piping racks foundations or supports sizing when carrying also for example ladder-type cable trays. Do the dynamic effects of short-circuits in cables need to be taken into account for sizing the supports?

I usually only used cable weight per length unit an so for calculating cable tray fill but no dynamic effects of short-circuit currents. I came across IEC 61914 standard about cable cleats that must be sized according to short-circuit currents but I have not found any standards about cable trays that mention dynamic effects of short-circuits for cable trays sizing.

Does anyone know if this topic is dealt in any IEC, IEEE, ICEA, NEMA standard?

 

[dpc]

I don't recall the cable SC forces being considered - I can't imagine it being an issue for a tray support system. But you do need to include a point load for someone standing on the tray, because that will definitely happen, and that person will generally be on the large side.

 

[jghrist]

If you have all three phases, neutral, and ground wire for each circuit in the same cable tray, then there will be no net force on the cable tray for a fault. The force is between the cables carrying the fault current.

 

[radug]

Hello,

It is a 220kV XLPE cable that will be laid in an existing rack. So they are 3 independent cables, one for each phase, that will be joined by cable cleats.

 

[7anoter4]

In my opinion it depends if there are individual clamps separate for each single core cable and then the force will strain the cable tray or a common clamp and then the force will stay in the clamp only.
In the first case the part of cable tray which is involved has to be calculated as per IEC 60865-1 Ch. 2.3 Flexible conductor arrangement.

 

[jghrist]

In my opinion it depends if there are individual clamps separate for each single core cable and then the force will strain the cable tray or a common clamp and then the force will stay in the clamp only.

If the single core cable clamps are in the same tray, there will be forces internally on the tray, but not on the tray supports.