EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: PiotrMisiuna on June 18, 2021, 07:10:30 pm
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A friend approached me with a following question:
he has a solar array with an inverter, powering house and sending surplus back to the grid.
In an event of grid power shortage, the main RCD gets instantly tripped and has to be reset manually.
Is there a way to detect power shortage and isolate inner grid proceeding the main RCD actuation, and automatically reconnect after detecting power get restored?
Nothing can be connected before the RCD.
I assume, that RCD tripping is here a feature, aiming to protect people working on the grid from presence of stray power.
Probably there already exist a solution, never the less I was considering using current sensing clamps like Dave showed in the video about solar analytics. https://www.youtube.com/watch?v=dxc5aHCVQzA&t=1422s (https://www.youtube.com/watch?v=dxc5aHCVQzA&t=1422s)
Somehow sense the difference between the two and trip a relay(probably solid state) connected right after the RCD
Give me your thoughts.
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How is all of this connected together? Is the RCD part of the standard panel as supplied by the utility, or is it part of the solar installation? The way houses are wired varies quite a bit around the world, which may affect your answer. When you say "grid power shortage", are you talking about a blackout, where the utility supply goes out entirely, or a "brownout", where the utility voltage sags significantly under load?
Depending on what is actually causing the RCD to trip, and whether that's a deliberate feature (I think a lot of--maybe most/all?--domestic PV inverters won't operate if they don't detect grid power anyway for safety reasons, and maybe the RCD is deliberately tripped to isolate the PV install for the same reason?), maybe a phase monitoring system that can detect an impending or partial utility power failure and isolate the panel from the utility supply before the utility equipment cuts out would help. Commercial/Industrial power systems use these to protect equipment or begin transferring to backup power in case of a utility undervoltage or partial phase loss. There's a wide range of options for various voltage ranges/phase counts/feature requirements. Random example: https://www.littelfuse.com/products/protection-relays-and-controls/protection-relays/voltage-monitoring-relays.aspx (https://www.littelfuse.com/products/protection-relays-and-controls/protection-relays/voltage-monitoring-relays.aspx)
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I am talking about RCD in the standard supplier utility. I haven't seen the installation for myself yet, but Cyprus grid and solar design standards would be closest to the one in the UK.
Yes I mean blackout.
As to PV, I assume my friend is able to run it independent... I guess..somehow... Why would he ask
I need to do my homework before I continue asking questions..