Maximum Allowable Conductor Temperature

Modified on Wed, 21 Sep 2022 at 09:13 AM

The maximum permissible temperature rise of earth conductors during a short circuit must be limited according to the type of material and connections or welds.  This is to ensure that the conductors, connections, and welds (a) don’t melt during a fault; and (b) their mechanical integrity is not adversely affected.


You should also refer to any of your client (utility) standards which may have requirements for short-circuit time and maximum allowable temperature.


Below is a screenshot of the grid conductor size calculator from SafeGrid Earthing Software based on IEEE Std 80:



Below is a related extract from BS 7430 which provides guidance:

Below is an extract from ENA EG-1:2006 Substation Earthing Guide (note there is a newer 2022 edition).



References:

BS 7430:2011+A1:2015 Code of practice for protective earthing in electrical installations

ENA EG-1:2022 Substation Earthing Guide

IEEE Std 80-2013 IEEE Guide for Safety in AC Substation Grounding

SafeGrid Earthing Software: https://elek.com.au/electrical-software/safegrid-earthing/


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