Project Overview
Potmans Lane is a 49.9MW battery energy storage system in East Sussex, connecting to the UKPN 132kV network. Like Halesworth, it's classified as Type D due to the high connection voltage.
What made this project unique was the discovery during studies that the battery inverters alone couldn't achieve the required power factor at full 49.9MW export. This required us to design a power factor correction solution to reach full capacity while maintaining G99 compliance.
The Challenge
During the load flow and reactive power analysis, we identified that the selected battery inverters had insufficient reactive power capability at full active power output. Without intervention, the project would either fail G99 compliance or be forced to curtail active power export.
The challenge was compounded by equipment changes during the project—the PCS (Power Conversion System) changed mid-project, requiring multiple design iterations.
Additionally, the project required NER (Neutral Earthing Resistor) sizing for transformer earth fault protection, adding another layer of complexity to the design.
Our Approach
We delivered the full G99 Type D package plus a dedicated PFC sizing study to resolve the reactive power limitation.
G99 Studies
- • G99 Load Flow Study
- • Short Circuit Study
- • P28 Voltage Fluctuation Study
- • G5/4 Harmonic Study
- • Cable Sizing Study
- • NER 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
PFC Sizing Study
Dedicated power factor correction analysis to determine the required capacitor bank sizing:
- • Reactive power gap analysis at full export
- • Capacitor bank sizing calculations
- • Harmonic impact assessment
- • Integration with overall plant design
Technical Highlights
PFC Sizing
Identified inverter reactive power limitation and designed capacitor bank solution to achieve full 49.9MW export with G99 compliance.
NER Sizing
Neutral earthing resistor sizing for transformer earth fault protection, ensuring safe fault current limitation.
Design Iterations
Multiple design rounds as equipment changed mid-project, maintaining compliance through PCS changes.
132kV Expertise
High voltage connection with full transformer protection suite and UKPN coordination.
Problem Solving in Action
This project demonstrates our approach to technical problem-solving. Rather than simply reporting that the inverters couldn't meet requirements, we identified the specific shortfall, designed a practical solution (PFC capacitor bank), and delivered a compliant design that achieved the project's full capacity target.
Results
The project achieved UKPN approval with the PFC solution in place, enabling full 49.9MW export capacity. The BESS is now fully operational.
"Completed for Smith Brothers"
Key Facts
- Capacity
- 49.9 MW
- Connection Voltage
- 132 kV
- G99 Classification
- Type D
- Location
- East Sussex, England
- DNO
- UKPN
- Completion
- 2023
- Status
- Operational
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