Project Overview
Fordtown is a 49.9MW battery energy storage system located in Scotland, connecting to the SSE distribution network at 33kV. While classified as a Type C connection under G99 (due to being under 50MW at distribution voltage), the project's proximity to the transmission network triggered additional Grid Code compliance requirements.
This created a unique dual compliance challenge: the project needed to satisfy both DNO requirements under G99 and TSO requirements under the NGESO Grid Code, including the BELLA (Bilateral Embedded Licence Exemptible Large Power Station Agreement) process.
The Challenge
Type C projects rarely require full TSO compliance—this is typically reserved for Type D connections (≥50MW or ≥110kV). However, Fordtown's grid location meant NGESO required the project to demonstrate compliance with Grid Code requirements including fault ride through, frequency response, and reactive power capability.
This meant delivering two parallel compliance packages: standard G99 studies for SSE, plus the more complex BELLA submission process with NGESO including harmonic analysis at transmission level (G5/5 rather than G5/4).
Our Approach
We delivered a comprehensive package covering both DNO and TSO requirements, coordinating between SSE and NGESO throughout the process.
DNO Studies (SSE G99)
- • G99 Load Flow Study
- • Short Circuit Study
- • P28 Voltage Fluctuation Study
- • Cable Sizing Study
- • Dynamic Study (RMS simulation)
TSO Studies (NGESO Grid Code)
- • G5/5 Harmonic Study
- • BELLA Documentation
- • UDFS (User Data File Submission)
- • PPC Model Development
Protection Studies
- • OCEF (Overcurrent Earth Fault) for all feeders
- • Incomer protection coordination
Note: No transformer protection required—33kV connection without power transformer.
Technical Highlights
Dual Compliance Path
Coordinated parallel submission processes with both DNO (SSE) and TSO (NGESO), managing different technical requirements and review cycles.
G5/5 Harmonic Analysis
More complex than standard G5/4, requiring harmonic impedance loci analysis at transmission level with multiple operating scenarios.
BELLA Process
Multiple submission rounds with NGESO Engineering Compliance review, requiring detailed technical responses and model updates.
Dynamic Modelling
Full RMS transient stability studies including PPC (Power Plant Controller) model development for Grid Code compliance demonstration.
Results
The project achieved successful approval from both SSE and NGESO after iterative review cycles. The BESS is now fully operational, providing grid services to the Scottish network.
Client: Eelpower Limited
Key Facts
- Capacity
- 49.9 MW
- Connection Voltage
- 33 kV
- G99 Classification
- Type C
- Location
- Scotland
- DNO
- SSE
- TSO
- NGESO
- Completion
- 2023
- Status
- Operational
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