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When is a PEI not a PEI?

AJJewsbury

"Prosumer" Electrical Installation that is - i.e. an installation that can both produce and consume electricity.

I've been looking over the new Part 8.

It seems to describe quite a sophisticated setup - a "smart" system if you like - dynamically changing things according to some pre-programmed algorithms - maybe to minimise imports, perhaps to export 'when the price is right', deciding whether storage (if present) should accumulate or release, or something else. There even seems to be a specific requirement that a PEI incorporate an 'Electrical Energy Management System' (EEMS) (822.4).

Which got me thinking - how does a conventional ("dumb") grid-tied PV system fit into this? - where the amount of power generated locally is uncontrolled (i.e. just depends on external variables such as sunlight) and the only "management" is what can be achieved using a length of copper and Ohm's Law (i.e. any surplus just gets exported).

Is the idea that such installations should be smarter in future, or is it just that the non-existent management system of a typical PV system can just scrape through as a 'minimal' EEMS?

    - Andy.

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  • Or in other words a decent earth is needed as ADS must work promptly with all possible combinations of internal and external supply and all the possible variations in Zs and pssc that implies.

    Part 2 defines "Earth" as the conductive mass of the Earth - but the earth loop on a TN system doesn't include The Earth - it's metallic all the way back to the star point. The actual resistance of the system to Earth on a TN system can be reasonably high (anything up to 20 Ohms, often in the region of 1 Ohm) so not really comparable with Zs when you're using overcurrent protective devices, not that the N conductor need any have particular resistance to enable ADS as it's entirely uninvolved.

       - Andy.

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  • Or in other words a decent earth is needed as ADS must work promptly with all possible combinations of internal and external supply and all the possible variations in Zs and pssc that implies.

    Part 2 defines "Earth" as the conductive mass of the Earth - but the earth loop on a TN system doesn't include The Earth - it's metallic all the way back to the star point. The actual resistance of the system to Earth on a TN system can be reasonably high (anything up to 20 Ohms, often in the region of 1 Ohm) so not really comparable with Zs when you're using overcurrent protective devices, not that the N conductor need any have particular resistance to enable ADS as it's entirely uninvolved.

       - Andy.

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