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Multiple solar installs on one building

Johno12345

I'm looking for some advice.

We have had a solar system installed with four groups of panels, going to inverters in four distant areas of the site. The installer has more or less walked.

It is a large install, I think about 1MW in total so the DNO is involved, they want to witness the shutdown. They are expecting a stop button at the ring main unit to shut all three down within 30 seconds. I think there should be a stop button near the fire panel or have them shut down with the fire alarm. Another thinks there should be a stop button next to each bank of inverters. 

I'm sure the correct answer is in there somewhere but as the inverters aren't linked, something additional is required. Solaredge want a fire cable linking all four banks of inverters together and a fire gateway on one bank, connected to a stop button or fire relay. This will require a lot of cable and not an easy job

I think the prefered option is to have a fire relay installed next to each bank of inverters, a fire gateway and then the fire alarm will shut them all down, and we can install a stop button next to the ring main unit to trigger the fire alarm, or a call point, and even call points next to each bank of inverters if we wanted, all considerably easier than anything else, and somewhat automated. 

I think the crux of the matter is what is legally required, can anyone point me in the right direction? 

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    Johno12345 said:
    about 1MW

    It may be important to know whether it's >1MWac, i.e. Type B per EREC G99, as the rules are different. Note that the DNO will be considering the AC inverter rating not the panel DC rating.

    It sounds like the multiple stop buttons come from differing objectives. Obviously I don't know the project, but as a starter, consider:

    1. The DNO may well have required an up-front G99 protection, or G100 reverse power backup protection, or ANM (or similar) shutdown capabiltiy that would necessarily be at the incomer or main HV switchboard. Exactly what is required here will depend on the project details and what was agreed with the DNO in advance. Some of these would require remote operation of switchgear, not with the inverters. There doesn't necessarily have to be a button as well but that would make testing a little easier.
    2. The Fire Risk Assessment (or insurer's policy) may require integration with the fire alarm to shut down the installation in the event of a fire alarm. Even if it doesn't, it's not a bad idea.
    3. A stop button locally to each inverter group isn't usually a requirement, but may have arisen from a site-specific risk assessment e.g. a means to quickly shut down if there was a problem on the roof, and it's neither a bad idea nor usually difficult to achieve even if it's as simple as shunt tripping MCCBs. Note that this is usually separate to a fire call point. Usually a local stop button would only shut down the local inverter group, but that does depend on what is being achieved.
    4. Not one that has been suggested but it's probably also worth asking whether there needs to be some interlocking with backup generator, if there is any... (of course that could be key exchange if electrical)

    Separately I wonder if SE are wanting comms to each inverter for a G100 Export Limitation Scheme, in which case you've not got any choice. Even if not, comms to each inverter is very sensible and while not required should really be the default anyway for an install of this size... otherwise how will you know if your 1MW generator isn't working?

    Some of this could be done with wireless comms (designed for fail-safety), but if we're talking a single large building that may not be sufficiently reliable and hard wiring is always preferred. Not all DNOs will accept it either.

    What was in the contract, and who was responsible for dealing with the DNO?

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  • 0
    Johno12345 said:
    about 1MW

    It may be important to know whether it's >1MWac, i.e. Type B per EREC G99, as the rules are different. Note that the DNO will be considering the AC inverter rating not the panel DC rating.

    It sounds like the multiple stop buttons come from differing objectives. Obviously I don't know the project, but as a starter, consider:

    1. The DNO may well have required an up-front G99 protection, or G100 reverse power backup protection, or ANM (or similar) shutdown capabiltiy that would necessarily be at the incomer or main HV switchboard. Exactly what is required here will depend on the project details and what was agreed with the DNO in advance. Some of these would require remote operation of switchgear, not with the inverters. There doesn't necessarily have to be a button as well but that would make testing a little easier.
    2. The Fire Risk Assessment (or insurer's policy) may require integration with the fire alarm to shut down the installation in the event of a fire alarm. Even if it doesn't, it's not a bad idea.
    3. A stop button locally to each inverter group isn't usually a requirement, but may have arisen from a site-specific risk assessment e.g. a means to quickly shut down if there was a problem on the roof, and it's neither a bad idea nor usually difficult to achieve even if it's as simple as shunt tripping MCCBs. Note that this is usually separate to a fire call point. Usually a local stop button would only shut down the local inverter group, but that does depend on what is being achieved.
    4. Not one that has been suggested but it's probably also worth asking whether there needs to be some interlocking with backup generator, if there is any... (of course that could be key exchange if electrical)

    Separately I wonder if SE are wanting comms to each inverter for a G100 Export Limitation Scheme, in which case you've not got any choice. Even if not, comms to each inverter is very sensible and while not required should really be the default anyway for an install of this size... otherwise how will you know if your 1MW generator isn't working?

    Some of this could be done with wireless comms (designed for fail-safety), but if we're talking a single large building that may not be sufficiently reliable and hard wiring is always preferred. Not all DNOs will accept it either.

    What was in the contract, and who was responsible for dealing with the DNO?

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