Higher temperature levels are now allowed under IS EN 61230:2008 to accommodate lighter equipment, the only consideration is that temperature levels do not produce poisonous gases in confined areas or areas where egress is inhibited.

The following tables may be helpful in the selection of properly sized earthing and short-circuiting conductors. 

300°C Rise in Temperature ESUY to IEC 61138

450°C Rise in Temperature ESUY to IEC 61138



Selection Criteria Summary:

  1. Establish fault current.   (See guide to fault levels and suitable earthing equipment)
  2. Establish tripping time and multiply by desired safety factor.
  3. Choose conductor size required from above tables.
  4. Ensure electro-magnetic forces and thermal stresses are satisfied.
  5. The effects of automatic re-closing breakers should be factored into joule heating calculations.
  6. Err on the side of safety.
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