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National Grid, Low frequency disconnecting system.

broadgage
As is fairly well known, any excessive drop in UK grid frequency results in calls for increased generation from quick starting plant such as OCGT and pumped storage, and for increased output from already running generating capacity.

If this does not relieve matters, then areas are disconnected by frequency sensitive relays in order to preserve the rest of the system. This last happened in August 2019 IIRC.


My question is what will happen during the NEXT low frequency event ?

Will the SAME areas be blacked out via the same (or similar replacement) relays operating the same switchgear as last time.

Or are settings adjusted after a low frequency event, such that next time the burden will fall on different areas.


The first approach sounds simpler, but the second approach is fairer. Or are such low frequency events so rare that "fairness" is not considered important.
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    Low frequency demand disconnection is still quite rare. Blocks of demand are programmed manually to be disconnected automatically at set frequencies. However once these frequencies are reached there is a certain randomness in which blocks actually trip depending on the sensitivity of each relay and the accuracy of it's operation. So the same blocks wouldn't necessarily trip each time. I believe that part of the review.is (was?) to consider what happens now that some 'demand' groups now actually export at least part of the time and tripping these groups (effectively generation) could be the wrong action when trying to contain a falling frequency. The LF relays were originally on the CEGB 132kV to Area Board interface and since most of the 132kV network is now owned by the DNOs then they are maintained and set by the DNOs in accordance with the Grid Code
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  • 0
    Low frequency demand disconnection is still quite rare. Blocks of demand are programmed manually to be disconnected automatically at set frequencies. However once these frequencies are reached there is a certain randomness in which blocks actually trip depending on the sensitivity of each relay and the accuracy of it's operation. So the same blocks wouldn't necessarily trip each time. I believe that part of the review.is (was?) to consider what happens now that some 'demand' groups now actually export at least part of the time and tripping these groups (effectively generation) could be the wrong action when trying to contain a falling frequency. The LF relays were originally on the CEGB 132kV to Area Board interface and since most of the 132kV network is now owned by the DNOs then they are maintained and set by the DNOs in accordance with the Grid Code
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