G59 Mains Protection Relays – ComAp

The world of mains protection is changing, with the introduction of EREC G99-1. G99-1 will replace G59-3.4 on the 27th April 2019. Learn more about this new recommendation from the ENA here.


What is mains protection?

G59 mains protection relays ensure the safe operation of generators and the grid. They isolate renewable and local power generation facilities such as solar, wind, hydro-electric and CHP sites from grid fluctuations.

The need for G59 mains protection

The drive to use environmentally-friendly electricity has changed the power generation landscape. Instead of relying on a relatively small number of high-capacity power stations, we are turning towards a much larger number of low-capacity generators. Wind farms, photo-voltaic (PV) solar sites and hydro-electric plants are replacing coal and oil power stations.

Mains protection is essential when generating ‘parallel-to-mains’

The rapid expansion of lower-capacity generators can cause the grid to become less stable and this risks damaging both the generator and the grid. Systems that run ‘parallel-to-mains’ must include a relay to decouple the generator from the grid if a problem arises with either.


This 2-minute video summarises the main facts about G59.

The standard that governs mains protection in the UK and Ireland is G59. G59 mains protection is an important regulatory standard for both network operators (DNOs) and power generators. For the DNOs and utility companies G59:

  • Ensures safe balanced operation of the distribution system.
  • Guarantees reliable delivery of high quality electricity.
  • Allows smooth involvement of the distributed generation.
  • Enables remote control of power supply sources.

For generating companies, G59 offers:

  • reliable protection of their plant.
  • simple and standardised implementation across the whole of the UK.


What can IPU do for you?

IPU supply the most advanced and popular products in the market: ComAp’s MainsPro and InteliPro.

Panel-builders, consultants, contractors as well as distribution network operators (DNOs) all trust and know the MainsPro and InteliPro. There are 3,000 installations of the MainsPro in the UK (and over 10,000 around the world), making it one of the most popular.

IPU’s G59 product manager Ian Wassman has been an integral part of the recent G59 updates. Because of this, the expertise we can offer to customers is second to none.


What’s the latest G59 news?

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.

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.

Learn more here.

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