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?
Just a thought here. Is there any provision which specifies voltage drop at HV. Surely, if HV is low, Lv must also be low?
May I also point out that the core requirement to achieve regards volt-drop are Regs 525.1 and 525.201
525.202 says that, if you do meed the guidance in Appendix 4, Section 6.4, you're deemed to comply with 525.1 and 525.201. But at the end of the day, do you comply with 525.1 and 525.201?
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)
I trust what you are saying is correct, but not following how this is applicable to the question.
What I'm trying to understand is how the designer of the installation specify the volt drop in terms of BS7671, when faced with the above scenarios? Assuming he has no knowledge of ESQCR.
The main aim is to ensure that the voltage drop in any circuit and in the whole installation does not exceed 4% of the nominal voltage, as required by Regulation 525.1 and 525.201. Appendix 4, Section 6.4 provides some recommended values for the voltage drop in each circuit, but they are not mandatory. They are only a way to achieve compliance with Regulation 525.1 and 525.201, but not the only way.
A private supply is defined by BS 7671 as a supply that comes from a non-public source of energy. Therefore, the second option in your question is the correct one. A private supply can be produced by different types of generators, such as PV, diesel/gas/nuclear, or batteries. The first option in your question is not a private supply, because it still depends on the public grid supply at the HV level. The private transformer only changes the voltage level, not the source of energy.
But aren't the sun and wind "public" energy? PV and turbines merely convert energy from one kind to another, rather than create it.
- Andy.
Assuming he has no knowledge of ESQCR.
The ESQCR should be freely available public knowledge -
https://www.legislation.gov.uk/uksi/2002/2665/contents/made
(including subsequent amendments:
https://www.legislation.gov.uk/uksi/2006/1521/contents/made
https://www.legislation.gov.uk/uksi/2009/639/contents/made
)
- Andy.
The main aim is to ensure that the voltage drop in any circuit and in the whole installation does not exceed 4% of the nominal voltage, as required by Regulation 525.1 and 525.201.
That's not what those Regulations say! The "main aim" is to make sure that the voltage drop is not so excessive that equipment becomes unsafe, or does not exceed the minimum voltage specified by the product standard.
The 4 % only comes in the guidance in Appendix 4, Section 6.4 (which is referenced in 525.202).
I agree with you that the 4% limit for the voltage drop in the installation is not a regulation, but a guidance that is given in Appendix 4, Section 6.4 of BS 7671. I also understand that other methods or calculations may be used to ensure compliance with Regulation 525.1 and 525.201, which are the core requirements for limiting the voltage drop in any circuit and in the installation.
Think we are drifting away from the question. What is a private supply in terms of BS7671? Option 1 or Option 2?
We're about to take you to the IET registration website. Don't worry though, you'll be sent straight back to the community after completing the registration.
Continue to the IET registration site
