Current carrying capacity of XLPE/SWA cables

Dutch of the Elm:

 

OMS:

Take a look at table 6 in BS EN 61439 - that should tell you that the allowable temperature rise on terminals is 70K (usually the ambient is 20C) - so compliant switchgear could easily be operating at 90C terminal temperature when at full load - which will clearly melt PVC.


XLPE insulated copper connected to compliant switchgear can happily run at 90C - you would expect the external surface temperature of the cable to be around 80C


 

Have you asked many switch gear manufacturer's if they would warrant such a situation?  How many would?  
Pretty well any manufacturer providing BS EN 61439 compliant switchgear - although I think we are at cross purposes - I was pointing out that the switchboard terminals at full load may already be at 90C - and that impacts the cabling. I think you are suggesting the opposite ie the cable is at 90C and influencing the terminals

My experience is that perhaps only Schneider, on certain devices, might concede to allow conductor temperatures rise to 90C. 
Have a read through the standard - temperature rise testing is now an integral part of the standard - many manufacturers struggle to comply with the requirements (and thus limit the cable temp to 70C, to give the switchgear some headroom

As far as a nay saying a"what if" argument, it is understandable that the conductor once arriving at the terminal would have had some unspecified opportunity to lose some heat.   However, as far as commercial risk goes, if the design (and therefore the designer) were already under some sort of scrutiny, it would be easy for someone to point to "incompatible" temperatures as a deficiency, unless of course you can prove by calculation that the conductor temperature will not significantly riser above 70C or that the switch gear manufacturer agreed that a rise to 90C is acceptable..

That temperature rise is specified in the switchgear standards - this should provide data on the terminal temperature and enclosure temperature - I agree that some manufacturers may limit conductor temperature to 70C to allow the heat input into the switchboard to not exceed the limits of the switchgear standard - but certainly not all

 

Dutch of the Elm:

 

OMS:

Take a look at table 6 in BS EN 61439 - that should tell you that the allowable temperature rise on terminals is 70K (usually the ambient is 20C) - so compliant switchgear could easily be operating at 90C terminal temperature when at full load - which will clearly melt PVC.


XLPE insulated copper connected to compliant switchgear can happily run at 90C - you would expect the external surface temperature of the cable to be around 80C


 

Have you asked many switch gear manufacturer's if they would warrant such a situation?  How many would?  
Pretty well any manufacturer providing BS EN 61439 compliant switchgear - although I think we are at cross purposes - I was pointing out that the switchboard terminals at full load may already be at 90C - and that impacts the cabling. I think you are suggesting the opposite ie the cable is at 90C and influencing the terminals

My experience is that perhaps only Schneider, on certain devices, might concede to allow conductor temperatures rise to 90C. 
Have a read through the standard - temperature rise testing is now an integral part of the standard - many manufacturers struggle to comply with the requirements (and thus limit the cable temp to 70C, to give the switchgear some headroom

As far as a nay saying a"what if" argument, it is understandable that the conductor once arriving at the terminal would have had some unspecified opportunity to lose some heat.   However, as far as commercial risk goes, if the design (and therefore the designer) were already under some sort of scrutiny, it would be easy for someone to point to "incompatible" temperatures as a deficiency, unless of course you can prove by calculation that the conductor temperature will not significantly riser above 70C or that the switch gear manufacturer agreed that a rise to 90C is acceptable..

That temperature rise is specified in the switchgear standards - this should provide data on the terminal temperature and enclosure temperature - I agree that some manufacturers may limit conductor temperature to 70C to allow the heat input into the switchboard to not exceed the limits of the switchgear standard - but certainly not all