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
Cases where G99 applies
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
The key steps in the application process are:
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.
Bill Rees
Bill Rees is the Director of Centrica Energy Assets, which is playing a leading part in shaping the UK’s net zero future, by delivering around 1GW of flexible energy assets.
Sign up to receive regular updates on:
By submitting your details you agree to process your personal data by Centrica Business Solutions as described on the Privacy Policy. Centrica Business Solutions will send you a regular newsletter and other marketing material we believe is relevant. You will be able to opt out of communications from us at any time.