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Steel Clad Building and High Voltage Overhead Cables.

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There is a modern sheet steel clad building nearby. It has what appears to be plastic covered steel sheets as exterior walls. It is used as a Scout Hut and can probably accommodate about 80 people for events. Running overhead are three high Voltage cables that feed local transformers, including the scout hut transformer which is on a pole nearby. The scout hut has two earth electrodes which connect to a part of the building and earth it. Although they are quite close together so may not really count as two in function.


Theoretically what would happen if one of the H.V. overhead cables came adrift and fell onto the roof of the building regarding risks?


This is a theoretical question relating to a real building but with a serious intention.


Thanks,


Z.


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    Theoretically what would happen if one of the H.V. overhead cables came adrift and fell onto the roof of the building regarding risks?



    I would expect the HV supply would most likely trip on earth fault (rather than by fuse or overcurrent CB) - it's one of the advantages of the UK HV system over the system used in the US as we don't distribute the N on HV - so any current returning to the star point at the HV source can only be due to an earth fault/leakage -so it's (relatively) simple to detect an HV earth fault and trigger disconnection. Not something to bet your life on of course - there's always the chance that the resistance to true earth is too high, or protective equipment faulty,  but in general most downed UK HV lines will be dead, while most US ones would likely still be live.


      - Andy.
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  • 0

    Theoretically what would happen if one of the H.V. overhead cables came adrift and fell onto the roof of the building regarding risks?



    I would expect the HV supply would most likely trip on earth fault (rather than by fuse or overcurrent CB) - it's one of the advantages of the UK HV system over the system used in the US as we don't distribute the N on HV - so any current returning to the star point at the HV source can only be due to an earth fault/leakage -so it's (relatively) simple to detect an HV earth fault and trigger disconnection. Not something to bet your life on of course - there's always the chance that the resistance to true earth is too high, or protective equipment faulty,  but in general most downed UK HV lines will be dead, while most US ones would likely still be live.


      - Andy.
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