GridServe performed a critical steady-state network assessment for the proposed 4.99MW Mansfield BESS. The study focused on evaluating the impact of a high-capacity inverter and integrated transformer connection to the AusNet distribution network, specifically analysing feeder capacity and voltage stability.
Key Project Scope & Deliverables
- Feeder Impact Analysis: Conducted steady-state studies on the 22kV feeder emanating from the Mansfield Zone Substation to determine the system’s ability to host 4.99MW of bi-directional power flow.
- Network Upgrade Modelling: Identified initial compliance failures in thermal loading and voltage variation, leading to the development of a comprehensive reconductoring strategy. This included:
- Replacement of overhead conductors with higher-rated AAC alternatives.
- Uprating existing sections to higher temperature ratings.
- Upgrading underground feeder exit cables to larger capacity LC cabling.
- Voltage Stability & Trip Analysis: Validated that with proposed upgrades, voltage variations at all feeder nodes remained within strict utility codes, including thresholds for 100% generation trip scenarios.
- Operational Control Strategy: Assessed the BESS under power factor control mode to optimize its interaction with the local network, particularly during low-load periods to mitigate voltage rise.
- Fault Level Assessment: Verified that the BESS connection-maintained fault levels within prescribed limits at both the Zone Substation and the Point of Connection (PoC).
- Grid Compliance Validation: Ensured all modelled outcomes aligned with AusNet technical requirements and the National Electricity Rules (NER).
Key Challenges
- Infrastructure Constraints: Managing initial “Fail” results where the 4.99MW import/export exceeded existing feeder thermal limits by over 35%.
- Dynamic Voltage Management: Addressing voltage rise during low-load conditions while leveraging the BESS to improve voltage profiles during peak-load periods.
- Complex Network Remediation: Engineering a multi-faceted reconductored solution (overhead and underground) to transition the project from a non-compliant state to a “Pass” across all thermal and stability criteria.
Technical Standards Followed
- NER (National Electricity Rules): Generator Performance Standards (GPS).
- AusNet Services Technical Standards: Distribution network connection guidelines.
- AS/NZS 3000: Electrical installations.