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Voltage drop in building networks

AJJewsbury
The recent posts about building networks has got me thinking - is there any recommendation for maximum permitted voltage drop within building networks?


Generally the DNO are allowed their +10/-6% variation and then BS 7671 generally allows 5% (or 3%) drop within the consumer's installation - and seemingly most ordinary appliances seemed to be based on a total of those - which is fine where the consumer's installation is directly connected to the DNO's system. But what about when there's maybe many tens of metres of extra cable involved courtesy of a BNO?


I guess that in the old days, when the distributor had responsibility all the way to the meter (so including the BNO as we'd now call it where the meter is at the consumer's end) the ESQCR limits would have applied at the meter terminals so the DNO would have had to designed to a tighter limit at the building's cutout - does anyone know if they still do that?


Otherwise there would seem to need to be some co-ordination between the design of the BNO and the consumer's installation - should the BNO formally 'declare' to the consumer's designer the v.d.? - perhaps as part of the tolerance on nominal voltage?


    - Andy.
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    As far as I know, the ESQCR limits apply at the outgoing meter terminals (or outgoing isolator terminals where the isolator is provided by the Meter Operator) regardless of whether there is a BNO between the intake and the meter. 



    Thank-you Alan, that's a very useful point.


    I take the point that by starting with a higher voltage at the transformer the distributors have a larger margin to play with - but I daresay there are a few situations where they've still used it up.


    Paperwork wise, I notice the ESQCR allows the option of agreeing in writing a different limit with the customer - so I guess it would be acceptable option for the BNO's v.d. to be added onto the DNO's (even if that took it over the normal 6% limit) - effectively obliging the customer's designer to work to tighter than normal limits for the customer's installation.


       thanks all

          - Andy.

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  • 0

    As far as I know, the ESQCR limits apply at the outgoing meter terminals (or outgoing isolator terminals where the isolator is provided by the Meter Operator) regardless of whether there is a BNO between the intake and the meter. 



    Thank-you Alan, that's a very useful point.


    I take the point that by starting with a higher voltage at the transformer the distributors have a larger margin to play with - but I daresay there are a few situations where they've still used it up.


    Paperwork wise, I notice the ESQCR allows the option of agreeing in writing a different limit with the customer - so I guess it would be acceptable option for the BNO's v.d. to be added onto the DNO's (even if that took it over the normal 6% limit) - effectively obliging the customer's designer to work to tighter than normal limits for the customer's installation.


       thanks all

          - Andy.

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