G59 required UK Generation owners to install loss of mains (LoM) protection at their generation sites. This is to ensure that, following a fault that isolates sections of the distribution system to which they are connected from the rest of the electricity system, distributed generation does not form an autonomous power island with the remaining local demand.

If the protection was not to work correctly, then major damage could be done when the isolated network re-joins the rest of the network due to the potential for out of phase switching. This is achieved is by having a dedicated loss of mains element in the protection relays.

Older relays work on a vector shift principle, but it has been proven over recent years that this is susceptible to nuisance tripping and there have been a number of occasions when a Grid Fault has caused many MW’s of generation to be incorrectly disconnected with the result that National Grid had to initiate emergency measures. New sites connected using G99 or recent sites under G59-3  are prohibited from using Vector Shift protection.

To mitigate the risk, National Grid run spare “spinning reserve” generating capacity at a cost exceeding £100m per annum.

To help reduce these nuisance trips, and lower the cost of the reserve generation National Grid and the ENA have stated that all sites will have to be converted from Vector Shift protection to Rate of Change of Frequency (RoCoF) by April 2022

Early adopters will both benefit from reduced outages and will receive an upgrade payment from National Grid for each site.

Payment will be in the order of £1k to £1.5k for relays that can have settings changed or between £2.5k and £4k if a relay must be changed.

To apply for the support funding, an application must be submitted to the DNO who will then assess the application against various criteria.  At the time of the application the details of the relays, make, type and settings will have to be provided along with other information.

If approved by the respective DNO, then the work can take place by competent contractors such as 33kV Ltd and once the evidence of the change has been provided, then payments will be made to the Generator by National Grid. The change can be done before agreement is reached with the DNO but evidence has to be provided that the relay change was needed (i.e. It was not already RoCoF) and it has been completed.

33kV Ltd can manage the entire process for you from making the application, site investigation to determine the type of change that is needed and then undertake the works for you.

While we undertake the changes, we can also provide you with a comprehensive protection relay health check using the latest technology and carry out an independent inspection and report on any identified anomalies or issues with the HV network

Contact info@33kv.com or call +44 (0) 1444 226 365 for more information.