Was talking to a switchboard manufacturer and he mentioned that the switchboards manufactured to BS 61439 are only tested to 70 degrees C, so all the cables attached to/from it must be calculated for 70 degrees. The only reference in the standard which makes some sense about this is section 10.2.3.1 attached. This means that all the XLPE cabling out there which is rated at 90 degrees is under-utilised and is useless.
Many designers I assume, are not aware and proceed in producing the calculations in Amtech or similar with cables to set operate at 90 degrees and think all is ok.
Amtech and the like are only as good as the user, SISO seems to apply here.
90 degree cabling can be useful where there are large temperature differentials throughout a run, a cable may pass through a thermally insulated section which may then raise its temperature under full load to 90 degrees, the terminations may still be at 60 degrees for example.
I recently requested of software company a cable thermal effects dialog where this could be modelled throughout a run, I can see plenty of use cases where increasing the CSA might be undesirable just for a section that may run hotter than 90% of the cable.
Amtech and the like are only as good as the user, SISO seems to apply here.
90 degree cabling can be useful where there are large temperature differentials throughout a run, a cable may pass through a thermally insulated section which may then raise its temperature under full load to 90 degrees, the terminations may still be at 60 degrees for example.
I recently requested of software company a cable thermal effects dialog where this could be modelled throughout a run, I can see plenty of use cases where increasing the CSA might be undesirable just for a section that may run hotter than 90% of the cable.
