GC0168: Submission of Electro Magnetic Transient (EMT) Models
What is being proposed
As Great Britain’s (GB) power system moves towards a net zero carbon operation; the number of Inverter-Based Resources (IBR) is expected to increase, with the amount of synchronous generation in the grid to decline which will significantly change the characteristics of the GB network. These changes give rise to the potential control interactions between the devices across the network leading to risks of oscillations and inverter stability. This modification seeks to require certain Users to provide the ESO with EMT models to enable analyses such as system oscillation, inverter stability and Transient Over Voltage (ToV)
Current status
Proposal raised and submitted to the March 2024 Grid Code Review Panel. The March 2024 Grid Code Review Panel unanimously agreed that GC0168 should follow the Standard Governance route and proceed to a Workgroup. The Panel approved the Terms of Reference for the Workgroup. Workgroup Nominations opened on 03 May 2024 and closed on 28 May 2024. The Proposer is exploring the solution further and completing work on stakeholder feedback, prior to commencing Workgroups. The time line has been revised along with an addition to the TOR, which will be presented to Grid Code Review Panel on 24 October 2024 The revised timeline and additional TOR was approved at the October Grid code Review Panel. The following Workgroup meeting was to review the Legal text and the Workgroup consulation. The Workgroup consultation was published on 23 January 2025, closed on 21 February 2025 and received 7 non-confidential responses and 2 confidential responses. The next Workgroup meeting is on 31 March 2025. The Proposer received some feedback on the modification legal text prior to the May Grid Code Review Panel, leading to a delay in presenting the Workgroup Report. The Workgroup Report was submitted in the June 2025 Panel Papers. The Panel did not agree that the Terms of Reference had been met, and asked for further review of the legal text by the Workgroup. A timeline update will be presented at the February Panel. 09/03/2026 The new timeline was approved at the February Panel.
Details
Timeline
Analysis
Grid Code modification GC0168 will require certain generators and network operators to provide electromagnetic transient (EMT) models to NESO for analysis of system stability as inverter-based resources displace synchronous generation. The modification follows standard governance through a workgroup process, with high impact on generators, transmission operators, distribution networks, interconnectors and transmission owners. Timeline has been repeatedly delayed, with workgroup report submitted June 2025 but Panel requesting further legal text review.
Why it matters
This represents a structural shift from voluntary to mandatory technical data provision as the system transitions to inverter-dominated operation. The repeated delays and legal text challenges suggest industry resistance to new compliance burdens, with generators bearing costs of model development while NESO gains enhanced system analysis capabilities for managing oscillation risks.
Key facts
- •Requires EMT models from generators, transmission operators, distribution networks, interconnectors
- •Enables analysis of system oscillation, inverter stability and transient overvoltage
- •Standard governance route through workgroup process
- •Timeline revised multiple times due to stakeholder feedback and legal text issues
- •Cross-code impact with CUSC