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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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  • well yes, we have noted before that the standards are not good at separating earthed objects that are also metallically connected and those that are earthed only by being stuck into terra-firma. (The obvious example is a  failure to distinguish between bonding to a water pipe that may carry significant diverted current voia a sub-ohm impedance to the neighbours , and to something like a bus shelter that will be  its own electrode of some tens of ohms at least. Both are identically classed as "extraneous conductors" variation in prospective current, and sensible cable size may be significant ..)

    However, if in this case BS7671 actually mean provide an electrode or equivalent buried metal suitable to operate the RCD or what have you, then that needs to be made explicit, and depending on the ADS arrangement, perhaps quite substantial undertaking. I would not have read it that way.

    M.

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  • well yes, we have noted before that the standards are not good at separating earthed objects that are also metallically connected and those that are earthed only by being stuck into terra-firma. (The obvious example is a  failure to distinguish between bonding to a water pipe that may carry significant diverted current voia a sub-ohm impedance to the neighbours , and to something like a bus shelter that will be  its own electrode of some tens of ohms at least. Both are identically classed as "extraneous conductors" variation in prospective current, and sensible cable size may be significant ..)

    However, if in this case BS7671 actually mean provide an electrode or equivalent buried metal suitable to operate the RCD or what have you, then that needs to be made explicit, and depending on the ADS arrangement, perhaps quite substantial undertaking. I would not have read it that way.

    M.

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