# NSW Approves 1,000 MWh Stoney Creek 8-Hour Grid-Forming BESS Connecting to Transgrid Narrabri Substation

> The New South Wales Department of Planning has granted full development consent to the 125 MW / 1,000 MWh Stoney Creek battery energy storage system, establishing one of Australia’s largest 8-hour duration grid-forming storage facilities directly interconnected to Transgrid’s Narrabri 132/330 kV substation.

- **Publish Date:** 2026-10-01
- **Category:** energy-storage
- **Reading Time:** 5 min
- **Original Source Citation:** [NSW Department of Planning & Transgrid Media](https://www.planning.nsw.gov.au/news/stoney-creek-1000mwh-bess-narrabri-substation-planning-approval)
- **Tags:** Transgrid, BESS, Australia Grid, Grid-Forming, Narrabri Substation, 1000 MWh, Synthetic Inertia, AEMO
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## Eight-Hour Long-Duration Storage Anchoring the North West Grid

Securing planning approval on October 1, 2026, the $450 million Stoney Creek project represents a critical milestone under the NSW Electricity Infrastructure Roadmap. Awarded a Long-Term Energy Service Agreement (LTESA) by AEMO Services, the facility is engineered to discharge 125 MW continuously across an 8-hour window (1,000 MWh), supplying deep firming energy during evening peak periods.

The facility connects directly into Transgrid’s existing Narrabri 132/330 kV substation via dedicated underground 132 kV cables and specialized step-up power transformers equipped with on-load tap changers (OLTC) and high seismic damping.

## Advanced Grid-Forming Inverters and Synthetic Inertia

The project deploys grid-forming (GFM) virtual synchronous machine inverters capable of true black-start support, autonomous voltage source operation, and instantaneous frequency droop response.

Electromagnetic transient (PSCAD) simulations verified that Stoney Creek’s synthetic inertia will stabilize voltage waveforms across the regional 330 kV network, allowing Transgrid to dispatch up to 600 MW of additional nearby wind and solar assets that were previously constrained by low system strength.

## Commercial Construction and Commissioning Timeline

Civil construction and site preparation at Narrabri are scheduled to commence in early 2027, with high-voltage electrical balance-of-plant contracts to be finalized by mid-2027. Full commercial operation is slated for late 2028, aligning with scheduled coal plant phase-outs across New South Wales.

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