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Solar PV into load side of RCD

lyledunn

At Section 8.8 in the COP for Grid connected Solar PV systems it clearly indicates that the inverter should not be connected to the load side of any RCD that is shared with other circuits. The note explains the reasons without elaboration.

I am trying to understand how an inverter would continue to supply the fault after the RCD has operated. Is it not a separated circuit at the loss of supply?

 

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    Imagine a split load consumer unit with a 30 mA RCD protecting a couple of circuits including sockets and the PV inverter. Now a fault occurs on the socket circuit such as a dodgy kettle. The RCD trips (within 300 ms) and that should protect the user from a lethal event. However.. the inverter should be shutting down as well but is not necessarily specified to do so as quickly as the RCD - so, briefly, the inverter may continue to feed 230 V into the fault. Making sure that the circuits do not share an RCD would avoid this scenario. This is my reading of what the CofP rule is about. There was a related thread a while ago, “RCD protection of a sub main with solar” (apologies I have not yet worked out how to insert a link to that!)

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    Imagine a split load consumer unit with a 30 mA RCD protecting a couple of circuits including sockets and the PV inverter. Now a fault occurs on the socket circuit such as a dodgy kettle. The RCD trips (within 300 ms) and that should protect the user from a lethal event. However.. the inverter should be shutting down as well but is not necessarily specified to do so as quickly as the RCD - so, briefly, the inverter may continue to feed 230 V into the fault. Making sure that the circuits do not share an RCD would avoid this scenario. This is my reading of what the CofP rule is about. There was a related thread a while ago, “RCD protection of a sub main with solar” (apologies I have not yet worked out how to insert a link to that!)

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