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Earth rod resistance

AlunW
Hi

Hoping someone can point me in the right direction!

On site we are trying to review our existing distribution earthing arrangements.  We have 11kV or 6.6kV distributed to local substations where we drop to 415v locally.  We generally have PNB systems with common HV equipment and LV neutral earth arrangements.  Typical one shown below
ebe497219bf639b0954936dc05b950cf-huge-substation-earthing-arrangements.png

I have reviewed several 'local authority' documents which suggest a maximum of 20ohms for earth rod resistance, but looking through BS EN 7430 it suggests on a similar arrangement in A.2 a maximum of 1 ohms?  Could anyone kindly advise what it should be? or point me in the right direction?

Many thanks

Al
Parents
  • 0
    Hi OMS

    Much appreciated for the guidance, we are in the process of having fault level analysis, step and touch potential studies carried out.  Would we expect the required earth rod resistance to be an outcome of this type of study?

    The E202 and E205 connections are both pre ct's at the moment and we are currently set for balanced rather than restricted earth fault protection, but looking at modding to REF in the near future. 

    Many thanks

    Al
Reply
  • 0
    Hi OMS

    Much appreciated for the guidance, we are in the process of having fault level analysis, step and touch potential studies carried out.  Would we expect the required earth rod resistance to be an outcome of this type of study?

    The E202 and E205 connections are both pre ct's at the moment and we are currently set for balanced rather than restricted earth fault protection, but looking at modding to REF in the near future. 

    Many thanks

    Al
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