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Prepare for new the G99 grid connection standard

What does the move from G59 to the replacement G99 standard mean for new embedded generation and battery storage connections?

The major shift from large centralised gas and coal generating plants to a decentralised model of smaller embedded generation and storage assets has created new performance challenges for the electricity network. These are being addressed via the transition to the new G99 grid connection standard.

With more solar and wind power entering the system, balancing supply and demand from these intermittent sources is more difficult. The phasing out of traditional generators, which provide system inertia for grid stability, is creating a further grid performance issue.

There is a pressing need for more active network management to meet all the complex performance criteria. That's why, on 27 April 2019, the G59 grid connection standard is being replaced with G99.

It will introduce new performance specifications to the connection and agreement process to ensure stability against grid faults, such as frequency, voltage and power factor, as well as optimising power quality. The specific requirements will vary according to the size of the generation or storage assets. These include: improvements in operational monitoring, such as more detailed interfaces with District Network Operators; together with measures to improve reactive power control and inject fast fault current.

Who will be affected?

The new standard will affect the design and planning process for all new wind, solar, CHP, and thermal generation grid connections with a rating above 16A/phase . The integration of battery storage will also be covered under the new standard .

Cases where G59 continues to apply

  • Assets currently connected under G59 agreements will see no immediate changes.
  • New generators scheduled for connection before 27 April 2019 will adhere to the G59 standard.

Cases where G99 applies

  • Those who have had a G59 application accepted, but have a connection scheduled on or after 27 April. However, if you can demonstrate you had a contract in place with your equipment supplier prior to 17 May 2018 and notify the DNO by 17 November 2018, you may still be permitted to connect under G59.
  • All new applicants.

Types of connection

G99 will divide generators and battery storage systems into four classes (A-D) and the compliance requirements will vary for each type.

The larger generating plants (above 10MW of capacity) will face the biggest changes and challenges in complying with the G99 standard. The changes will be less onerous for those with generating capacity below 10MW, especially generators rated below 1MW, which are likely to face minimal changes in design and specification.

Type A Generators or storage: < 1MW and < 110kV

Type B Generators or storage: 1MW - 10MW < 110kV

Type C Generators or storage: 10MW - 50MW < 110kV

Type  D Generators or storage: 50MW + < 110kV

G99 Compliance process

The key steps in the application process are:

  1. Complete new more complex G99 application form, according to your asset class (A-D)
  2. Provide 'compliance verification form' after connection accepted (this is a combination of testing, type testing, manufacturers' information, and design data & models
  3. Complete new onsite commissioning form
  4. Complete new commissioning completion certification form

As with any regulatory transition, there can be confusion around interpreting new rules and 'bedding-in' new compliance requirements and systems. As such, you may need to allow more time to obtain approvals and secure your connection date.G99 will also make the application process more complex and time consuming.

Centrica Business Solutions can provide support to customers through the G99 compliance process. Please contact your Centrica Business Solutions representatives if you wish to discuss how the above impacts your generation projects.

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