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No isolator

lyledunn
There is no main isolator upstream of a Mains / generator contactor changeover arrangement at the intake of a small industrial facility. There is also a separate contactor  set up which relates to the PV system which is connected directly to the mains input to the changeover contactor. I see this situation quite frequently but it it is clear that maintenance cannot be safely undertaken In either device without pulling the DNO fuses. My report indicated an unsatisfactory arrangement. The client then contacted the installer who informed me that it was common for them to do this where there was no main isolator provided. I avoid arguments and simply refer to my report which sets out the reason for my determination and any regulatory reference. Have you come across similar?

By the way, I tried to upload an image but the simple process that previously facilitated this has been changed. It would assist greatly if someone could tell me how this is now done (from an IPad)
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    lyledunn:

    Also,

    would you know what the name of this device is? It is associated with the PV system. That is mains directly in to top


    Looks to me like what many would refer to as a "G59 relay" / "G99 relay" * comprising a Comap MainsPro loss-of-mains protection relay and associated contactor. It will be providing over-/under voltage & frequency and either vector shift or rate-of-change-of-frequency (depending on vintage though vector shift would require a change due to retrospective changes to the Grid Code), and will disconnect the PV array if there is a grid disturbance. It should be properly documented on site and if there aren't accurate SLDs then you should ask the installer to supply them! Setting changes require DNO approval.


    In principle connecting the PV upstream of the genny c/o is sensible as it prevents adverse interactions with the generator. The alternative is some form of interlock to prevent the inverters generating while the genset is running.


    However re isolators it doesn't sound promising. I would expect the "G59 relay" to incorporate isolation and/or for there to be a point of isolation for the generator upstream. Ditto overcurrent & fault protection... I don't have the Blue Book to hand to quote from but I wouldn't accept that enclosure facing the DNO fuse without additional switchgear & protection. There should also be four-pole isolation for the PV array but if not combined with the above it could be closer to the inverter(s); personally I prefer it to be near the point of connection to facilitiate maintenance.of the rest of the installation.


    I came across similar not very long ago, being asked to design new circuits on an existing installation with the C/O and busbar chamber relying on the DNO fuses, but since my design scope (several tiers away from the Client) did not reach that far I was only able to advise that it merited a review. In that case the generation was being fitted protected by MCCBs so isolation and protection of the PV wasn't a concern.


    * The name's a slight misnomer, because the enclosure includes more than just the relay. Sometimes it's a whole distribution board! Meanwhile G59/G99 require far more than just an interface protection scheme...


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  • 0
    lyledunn:

    Also,

    would you know what the name of this device is? It is associated with the PV system. That is mains directly in to top


    Looks to me like what many would refer to as a "G59 relay" / "G99 relay" * comprising a Comap MainsPro loss-of-mains protection relay and associated contactor. It will be providing over-/under voltage & frequency and either vector shift or rate-of-change-of-frequency (depending on vintage though vector shift would require a change due to retrospective changes to the Grid Code), and will disconnect the PV array if there is a grid disturbance. It should be properly documented on site and if there aren't accurate SLDs then you should ask the installer to supply them! Setting changes require DNO approval.


    In principle connecting the PV upstream of the genny c/o is sensible as it prevents adverse interactions with the generator. The alternative is some form of interlock to prevent the inverters generating while the genset is running.


    However re isolators it doesn't sound promising. I would expect the "G59 relay" to incorporate isolation and/or for there to be a point of isolation for the generator upstream. Ditto overcurrent & fault protection... I don't have the Blue Book to hand to quote from but I wouldn't accept that enclosure facing the DNO fuse without additional switchgear & protection. There should also be four-pole isolation for the PV array but if not combined with the above it could be closer to the inverter(s); personally I prefer it to be near the point of connection to facilitiate maintenance.of the rest of the installation.


    I came across similar not very long ago, being asked to design new circuits on an existing installation with the C/O and busbar chamber relying on the DNO fuses, but since my design scope (several tiers away from the Client) did not reach that far I was only able to advise that it merited a review. In that case the generation was being fitted protected by MCCBs so isolation and protection of the PV wasn't a concern.


    * The name's a slight misnomer, because the enclosure includes more than just the relay. Sometimes it's a whole distribution board! Meanwhile G59/G99 require far more than just an interface protection scheme...


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