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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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    FlyWheel:

    But of course, getting the supply limit data out of them before such a situation is detected, may be like trying to get blood out of a stone, so I suggest assuming their supply fuse represents that "ultimate" limit is not unresonable.




    They should know the ASC for every property, whether specifically applied for, or a default. The information is needed for the calculations for a new connection, to determine what (if any) network reinforcement is required as part of the quote. It is likely that the ASC will be less than the supply fuse. Some DNOs in the UK fitted a 100A fuse regardless, others tried to fit a fuse closer to the ASC. 


    Whether the DNO were aware of all the additional load tagged on is questionable, however it will be obvious from the voltage / current traces they have, together with a rough size of the motor loads, and their start / stop regimes. The cost of the supply upgrade will depend on what is needed to deliver three phase to the property. It may be easy, or it may be difficult (read “expensive”). 


    Regards,


    Alan. 

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  • 0

    FlyWheel:

    But of course, getting the supply limit data out of them before such a situation is detected, may be like trying to get blood out of a stone, so I suggest assuming their supply fuse represents that "ultimate" limit is not unresonable.




    They should know the ASC for every property, whether specifically applied for, or a default. The information is needed for the calculations for a new connection, to determine what (if any) network reinforcement is required as part of the quote. It is likely that the ASC will be less than the supply fuse. Some DNOs in the UK fitted a 100A fuse regardless, others tried to fit a fuse closer to the ASC. 


    Whether the DNO were aware of all the additional load tagged on is questionable, however it will be obvious from the voltage / current traces they have, together with a rough size of the motor loads, and their start / stop regimes. The cost of the supply upgrade will depend on what is needed to deliver three phase to the property. It may be easy, or it may be difficult (read “expensive”). 


    Regards,


    Alan. 

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