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Volt drop % - Private Supply Def

Peter Hartley

Good day everyone 

Public supply Volt drop 3% Lighting 5% Power.

Private supply Volt drop 5% Lighting 8% Power.

Define private supply?

Option 1 - HV public grid supply to privately owned transformer. Is LV supply private?

Option 2 - Main source of supply is from Privately owned source of generation such as PV, diesel/gas/nuclear generator?

Why is this not defined in BS7671?

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  • 0
    Chris Pearson said:
    Just a thought here. Is there any provision which specifies voltage drop at HV. Surely, if HV is low, Lv must also be low?

    No specific provision in BS 7671 ... and agreed, but transformers with tap-changers and AVC can be used to overcome that (or, in the LV system, autotransformers with tap-changers)

  • 0 in reply to gkenyon

    Think we are drifting away from the question. What is a private supply in terms of BS7671? Option  1 or Option 2?

  • 0 in reply to Peter Hartley
    Peter Hartley said:
    Think we are drifting away from the question. What is a private supply in terms of BS7671? Option  1 or Option 2?

    Anything other than a "standard" ESQCR public LV supply is the answer. Not drifting, that was answered earlier, and the discussion progressed beyond it.

  • 0 in reply to Peter Hartley

    I have searched the web and found the definition of a private supply according to BS 7671. A private supply is a supply that comes from a source of energy other than a public electricity supply system, This definition is also in agreement with the one given in [Wikipedia], which references BS 7671:2018 as its source. However, I could not find the exact location of this definition in the BS 7671

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  • 0 in reply to Peter Hartley

    I have searched the web and found the definition of a private supply according to BS 7671. A private supply is a supply that comes from a source of energy other than a public electricity supply system, This definition is also in agreement with the one given in [Wikipedia], which references BS 7671:2018 as its source. However, I could not find the exact location of this definition in the BS 7671

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  • 0 in reply to AMK
    AMK said:
    I have searched the web and found the definition of a private supply according to BS 7671.

    Why? Part 2 of BS 7671 contains the definitions within that standard?

    Also, what does "Wikipedia" define as a "source of energy" ?

    Wikipedia cannot interpret standards for us, I'm afraid.

    AMK said:
    However, I could not find the exact location of this definition in the BS 7671

    I'm not sure it's there.

    If you take the diagrams in BS 7671 at face value, a transformer is a 'source of energy' which further supports the explanation I have given that a "private transformer" is a "private source of energy" - or, if you like, a private supply.

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