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  • Loss of Mains (LoM)

  • What is it?

    Loss of Mains Protection operates to reduce the risk of a generator running ‘islanding’: where a section of the network is cut off from the wider network. The protection should only operate in an ‘islanded’ situation but occasionally, and more recently more often, it has operated for other network faults causing nuisance tripping for generators and the wider network. Previously vector shift and very sensitive RoCoF equipment was used as protection, but network events in 2018 and 2019 have identified the need for different protection measures.

    What does it mean for me and my connection?

    All already connected generators will require to review their Loss of Mains protection to ensure they comply with the new measures.  If you are using vector shift or more sensitive RoCoF then you will need to disable, modify or even replace your protection to ensure the required settings are in place by the 1st September 2022. This will bring all generators in line with new standards, many of which have been in place for connecting generators over 5MW since 2014.

    The Accelerated Programme allows most generators not yet complaint with the new requirements to apply for funding towards the cost of modifying or installing the new protection settings.


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