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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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    perspicacious:
    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.

    3? The building has only ONE service connected, if more than one service is required due to the building being split into individual units (terrace like), those subsequent services can only be TT?


    True or false?


    Regards


    BOD


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


    If the answer is "it doesn't matter" (from the DNO perspective), and the TT earthing arrangement is not properly separated, then we are in a tricky situation in cases where the PME earthing system is not connected to the HV earthing system at the supply transformer, as the statement Uf = 0 in Table 44.1 of BS 7671 is no longer always true !


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  • 0
    perspicacious:
    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.

    3? The building has only ONE service connected, if more than one service is required due to the building being split into individual units (terrace like), those subsequent services can only be TT?


    True or false?


    Regards


    BOD


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


    If the answer is "it doesn't matter" (from the DNO perspective), and the TT earthing arrangement is not properly separated, then we are in a tricky situation in cases where the PME earthing system is not connected to the HV earthing system at the supply transformer, as the statement Uf = 0 in Table 44.1 of BS 7671 is no longer always true !


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