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An interesting issue with a TT supply

Alan Capon
An interesting real life example of why you need double pole switching with a TT supply. The scenario is a small village with a few customers supplied by a single pole mounted transformer. 


We got a call from an electrician working in a property who had measured 400V phase to earth, 210V neutral to earth, and 241V phase to neutral, and was understandably worried. Any suggestions of what I tracked the fault down as? This can happen on any TT supply, but is fortunately very rare - I have come across it three times in 20 years. 


Regards,


Alan.
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  • 0
    Would a simple clamp meter around all the conductors supplying a consumer indicate whether the problem lay in their installation

    Indeed -  a sort of wire area measuring RCD idea.

    I presume there are some cable arrangements that make it impractical like overhead split singles, though you could use single current clamps with their secondary windings  in series opposition to give a zero sum. - indeed on HV exactly this sort of thing is commonly done to detect line faults.

    M.
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  • 0
    Would a simple clamp meter around all the conductors supplying a consumer indicate whether the problem lay in their installation

    Indeed -  a sort of wire area measuring RCD idea.

    I presume there are some cable arrangements that make it impractical like overhead split singles, though you could use single current clamps with their secondary windings  in series opposition to give a zero sum. - indeed on HV exactly this sort of thing is commonly done to detect line faults.

    M.
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