G59 Installation Loss of Mains Changes & How it Affects You!

Loss of Mains Change Programme Logo

If you have installed renewable generation before 1st February 2018 in accordance with EREC G59 requirements, then it is likely you will need to undertake an update.

The "Accelerated Loss of Mains Programme (ALoMCP)" is being led by National Grid and run by Distributed Network Organisations (DNO's) & Independent Distribution Network Organisations (IDNO's). 

Covering the United Kingdom but excluding Northern Ireland; it aims to reduce the risk of spurious tripping of the protection system. For renewable electricity generators, this means realigning the RoCoF limits (rate-of-change-of-frequency) in their generation equipment.

If you are a domestic generator of power, then thankfully this does not affect you. However, if you generate & sell back to the grid, using wind generators, hydro or solar PV, means you have until 31st August 2022 to implement the necessary changes. Failure to do so may open you up to an enforcement programme.

Why the change?

RoCoF or Vector Shift (VS) relays usually provides Loss of Mains Protection to prevent "power islanding." RoCof relays were programmed to trip when sensing changes of frequency as low as 0.125Hz. Both these and Vector Shift relays have found to respond to transmission faults that do not cause power islanding leading to low demand disconnections.

Who is responsible for the change implementation?

It's intended that the generators will undertake the settings changes themselves through their qualified contractors. Where a generator doesn't have these facilities, contractors such as ourselves are here to help. Instrument Transformers Limited in partnership with Switchgear Services & Solutions Limited offer changes & complete testing in accordance with the Accelerated LoM programme. Or where necessary, removal of existing LoM relay and install a new relay that is compliant with the new LoM requirements.

Generators can recover the cost of making these changes directly via an online portal located on the Distribution Network Operators (DNO), Independent Distribution Network Operators (IDNO), Energy Networks Association (ENA) & National Grid (NG) websites.

The rates paid for the work will vary from:

£1,000 to £1,500 for change in settings.

£2,500 to £4,000 for a relay change.

Payments will be fixed-rate rather than individual circumstances and are on a first-come, first-serve basis.

Still got questions?


or check out more information on the ENA Website Loss of Main Change Programme.

Loss of Mains process at a glance

LoM process at a glance