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Topic Title: Current Carrying Capacity for 90deg XLPE ref method 100
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Created On: 02 October 2017 04:39 PM
Status: Read Only
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 Current Carrying Capacity for 90deg XLPE ref method 100   - synapse - 02 October 2017 04:39 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - AJJewsbury - 02 October 2017 05:07 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - weirdbeard - 02 October 2017 05:57 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - mapj1 - 02 October 2017 07:27 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - synapse - 05 October 2017 10:30 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - ArduinoXR - 06 October 2017 01:22 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - leckie - 06 October 2017 05:23 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - OlympusMons - 06 October 2017 07:37 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - Alcomax - 06 October 2017 08:45 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - leckie - 06 October 2017 09:07 PM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - AJJewsbury - 07 October 2017 08:21 AM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - OlympusMons - 07 October 2017 10:52 AM  
 Current Carrying Capacity for 90deg XLPE ref method 100   - AJJewsbury - 08 October 2017 09:49 AM  
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 07 October 2017 08:21 AM
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AJJewsbury

Posts: 15838
Joined: 13 August 2003

You don't have to increase the csa of the whole cable, just the bits of it that are in contact with the insulation.

The conductor temperature doesn't change sharply at the surface of the insulation though - the cable outside the insulation acts as a heatsink lowering the conductor temperature for some distance into the insulation while the higher temperature within the insulation increases the conductor temperature outside the insulation for a similar distance. The actual distances involved will depend on a lot of factors including the cable c.s.a. but typically you'd be looking at about half a metre each way before getting to nominal operating temperatures.

A Wiring Matters article from 2006 dealt with this - http://electrical.theiet.org/w...t-ratings.cfm?type=pdf (note that BS 7671 rating have been revised since then).

The bottom line being you need to have about half a metre of cable outside of the thermal insulation before an accessory.for the approach to work properly.

- Andy.
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