Hallidays Hydro Maintain Implementing G99 Accelerated Loss of Mains Upgrades

The Accelerated Loss of Mains Programme is a project affecting renewable energy generators across Great Britain, excluding Northern Ireland. It requires all hydro schemes, solar PVs, and wind turbines to be upgraded to use Loss of Mains protection. The project is the result of changes under G99/1-4 and affects all G59 protection relays installed before February 2018.

Why It Is Necessary

Vector shift (VS) or ROCOF (rate of change of frequency) relays have been the standard technology used in the Loss of Mains protection. Their purpose was to prevent the formation of power islands, and they were expected not to trip, especially under transmission faults.

However, both of them were found to fail in the second requirement. Besides, ROCOF was designed to trip under frequency changes as low as 0.125Hz/s. If not rectified, these can lead to unnecessary loss of demand through low-frequency demand disconnection. Since there are over 50,000 distribution generators using this technology, such occurrences can significantly compromise the security of energy supply, which is about 15GW.

The Required Upgrades

The Accelerated Loss of Mains Programme aims to reduce the risk of unnecessary tripping. The first remedy is the removal of VS relays, where they are being used for Loss of Mains protection. They are to be replaced with ROCOF relays, which have better fault protection.

In spite of this preference, ROCOF relays have low sensitivity limits. The G99 Accelerated Loss of Mains Programme requires that the sensitivity of ROCOF relays be adjusted to 1Hz/s, which is the accepted level by the Distribution Code.

The programme began in August 2019 and is expected to run until April 2022, though it is advisable to make the changes as soon as possible. New hydro power generators are required to adhere to these requirements as well.

How Hallidays Hydro Maintain Can Help

Hallidays Hydro Maintain helps hydro power generating companies to upgrade their system to meet the new requirements by doing all the work for them. The services include:

  • Assessment and applying for funds: It involves assessing the power plant and working out the economics of the upgrade. Hallidays shall then write proposals applying for grant funding to start the project or refund once the update is complete, provided the power plant meets the criteria.
  • Maintenance manuals: Hallidays Hydro Maintain shall prepare the documentation of the new ROCOF relays and complementary systems to create maintenance procedures and instructions.
  • Training operatives: Hallidays Hydro Maintain will train your on-site operators on how to carry out low-level maintenance; it will reduce expenses on call-out fees.
  • Scheduled health checks: Hallidays Hydro Maintain shall offer scheduled visits to check the status of the new Loss of Mains protection system and ensure optimum operation and resolve any budding issues.
  • Remote monitoring: Hallidays’ experienced staff will offer remote support for issues that do not require an engineer to be on the site. They will also provide suggestions on necessary system updates and make any necessary system tweaks.

Hallidays Hydro Maintain offers all the necessary support and expertise to implement the G99 Accelerated Loss of Mains requirements. Contact Hallidays Hydro Maintain today for more information on 0330 1331 555 or email enquiries@hydromaintain.com.