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Minimum Voltage at incoming supply point

FlyWheel
Retired now and not up to date with reg’s since 16th. Helping advise a friend. Currently they have 100amp single phase supply and whilst the no load voltage is up at around 238 volts, as the circuit is loaded, voltage drops off substantially. Even with a load of 50 amps, ie, half the supply fuse rating, voltage is slightly below the -6% limit, at around 215 volts, further load simply pushes voltage significantly lower, and by extrapolating measured data, it would be nearer 170 volts with a load of 100 amps, is this acceptable? I plan measuring Ze and pfc this week as a guide perhaps to supply loop impedance and, which I suspect must be causing this excessive drop. I’m aware of the ESQCR reg’s although need to update myself, but are there any other regulations that apply?

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    It sounds unacceptably low.

    Before complaining though, do try and ascertain what the agreed supply capacity is. It might be a lot less than is implied by the 100 amp cut out fuse holder.

    Have you seen the fuse rating ? It might be a lot less than 100 amps. Or the fuse fitted might be larger then it should be.


    If the supply voltage is persistently below the minimum with the load not exceeding that agreed, then there would seem to be cause for complaint to the DNO.

    I presume that the voltage was measured at the point of supply, or reasonably close thereto and not at the far end of a long or marginally sized customer owned sub main. And that the instrument used is preferably calibrated recently.
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  • 0
    It sounds unacceptably low.

    Before complaining though, do try and ascertain what the agreed supply capacity is. It might be a lot less than is implied by the 100 amp cut out fuse holder.

    Have you seen the fuse rating ? It might be a lot less than 100 amps. Or the fuse fitted might be larger then it should be.


    If the supply voltage is persistently below the minimum with the load not exceeding that agreed, then there would seem to be cause for complaint to the DNO.

    I presume that the voltage was measured at the point of supply, or reasonably close thereto and not at the far end of a long or marginally sized customer owned sub main. And that the instrument used is preferably calibrated recently.
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