Project Overview
Halesworth is a 48.8MW battery energy storage system in Suffolk, connecting directly to the UKPN 132kV network. Despite being under 50MW, the project is classified as Type D due to the high connection voltage (≥110kV), triggering the full Type D compliance requirements.
The 132kV connection includes a dedicated power transformer, requiring comprehensive protection coordination studies beyond the standard G99 package.
The Challenge
132kV connections present unique challenges compared to typical 33kV distribution connections. The higher voltage level requires more rigorous fault level analysis, and the inclusion of a power transformer means a full protection study suite is needed.
Additionally, coordination with UKPN's 132kV network requirements and multiple equipment suppliers required careful data management throughout the project.
Our Approach
We delivered a complete G99 Type D compliance package plus the full transformer protection study suite required for 132kV connections.
G99 Studies
- • G99 Load Flow Study
- • Short Circuit Study
- • P28 Voltage Fluctuation Study
- • G5/4 Harmonic Study
- • Cable Sizing Study
- • Dynamic Study (RMS simulation)
Protection Studies
- • OCEF (Overcurrent Earth Fault)
- • SBEF (Standby Earth Fault)
- • Transformer Bias Differential
- • Transformer HV REF
- • Transformer LV REF
Technical Highlights
132kV Connection
High voltage grid connection requiring comprehensive fault level analysis and coordination with UKPN's transmission-level network.
Transformer Protection
Full transformer protection coordination including bias differential, HV REF, and LV REF protection schemes.
Type D Classification
Classified as Type D due to 132kV connection voltage (≥110kV threshold), despite capacity being under 50MW.
DNO-Only Compliance
Embedded within UKPN network, so no separate TSO/Grid Code requirements—streamlined single compliance path.
Results
The project achieved UKPN approval and is now fully operational, providing grid services to the East Anglia network.
Client: Eelpower Limited
Key Facts
- Capacity
- 48.8 MW
- Connection Voltage
- 132 kV
- G99 Classification
- Type D
- Location
- Suffolk, England
- DNO
- UKPN
- Completion
- 2023
- Status
- Operational
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