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Metal - clad buildings and the confused forum member.

UKPN
One of the members has queried ESQCR bonding/earthing PME requirements for the above. So its worth spending a little time putting across the companies requirements. Where metal-clad buildings incorporate a steel-frame that utilises steel vertical beams that are within the foundations, the steel frame will provide a good connection with the earth which will effectively limit the earth potential rise.

A PME service may be provided to a metal-clad building provided the following criteria are satisfied:


1. The metal cladding is bonded to the steel-frame.

2. The supply is either three-phase with less than 40% unbalance or the supply is single - phase and the frame to earth impedance is les than 20ohms.

Regards, UKPN?

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    Alan Capon:
    gkenyon:


    That's very interesting ... how is the TT installation immediately adjacent to the PME supplied installation separated from the PME earthing system?


    For us, the issue would be two or more PME services into different areas of a steel building. It would be possible for the steelwork of the building to carry diverted neutral currents, for which it almost certainly would not be rated. 


    Regards,


    Alan. 




    That I understand.


    However, connecting extraneous-conductive-parts to the MET (or inadequate separation of the TT earthing system) effectively connects the installation to PME, This may cause a problem for either diverted Neutral currents in the LV system as before (the TT earth electrode resistance may be very small, and if not properly separated ... it's pretty much connected?). Also, the issue I pointed out previously.


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  • 0
    Alan Capon:
    gkenyon:


    That's very interesting ... how is the TT installation immediately adjacent to the PME supplied installation separated from the PME earthing system?


    For us, the issue would be two or more PME services into different areas of a steel building. It would be possible for the steelwork of the building to carry diverted neutral currents, for which it almost certainly would not be rated. 


    Regards,


    Alan. 




    That I understand.


    However, connecting extraneous-conductive-parts to the MET (or inadequate separation of the TT earthing system) effectively connects the installation to PME, This may cause a problem for either diverted Neutral currents in the LV system as before (the TT earth electrode resistance may be very small, and if not properly separated ... it's pretty much connected?). Also, the issue I pointed out previously.


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