Changes to G59 bring a high demand for MainsPro Mains Protection Relay

September 18th, 2018

With new changes to G59 (G59-3.4) and the implementation of G99-1, here’s a quick recap of the requirements and how you can help us with the high level of demand we’re experiencing for relays.


Current requirements: G59-3.4

As many of you are aware, G59-3.4 came into effect in July 2018:

G59-3.4 July 2018 Modification to disallow the future use of Vector Shift protection and to provide new RoCoF requirements

To ensure stability of the grid, DNO’s are pushing hard for upgrades to the new RoCoF setting to take place quickly.


Future requirements: G99-1

G99-1 was announced in July 2018 and comes into effect from 27th April 2019.

G99-1 July 2018 Requirements for the connection of generation equipment in parallel with public distribution networks on or after 27 April 2019

Equipment that is compliant with G99 can be connected in advance of 27th April, as it will also comply with the pre-existing G59-3.4 requirements.

After the 27th April 2019, you will be unable to connect using equipment that is compliant with G59-3.4 only.

The ComAp MainsPro and InteliPro mains protection relays are compliant to both G59-3.4 and G99-1 non type-tested equipment. Installing these relays will help to future proof your sites against these upcoming changes in requirements.


Ordering 3 or more MainsPro relays

We are currently experiencing an increase in demand for the MainsPro relay.

If you have any pending projects that need 3 or more MainsPro relays, please send a schedule (including volume and delivery date) to Ian Wassman at

Doing this will ensure we can manage our stock efficiently in this period of high demand.

For further information on the changes to requirements, please contact Ian directly. Thanks to Ian’s involvement in a G59 Working Group tasked with disallowing Vector Shift protection, his expertise on the subject is second to none.


What is mains protection and why is it important?

This short animation gives you an overview of mains protection.

Please note: should you no longer require the relays, we will not hold you to any schedule provided.