Powerlink Seeks Approval to Connect AGL’s 500MW Battery

• Powerlink seeks approval for an underground link to AGL’s 500‑MW/2,000‑MWh battery, fast-tracking Queensland grid stability, firming renewables and peak-demand support with minimal surface impact.

Queensland’s state-owned grid operator Powerlink has applied for environmental approval to install underground infrastructure to connect a planned utility-scale battery to the transmission network. The proposal would link AGL Energy’s 500‑MW/2,000‑MWh battery energy storage system, advancing grid stability and peak demand support in the state.

The works would enable export and dispatch of stored power from the AGL project once built, though detailed timelines and costs were not disclosed. The application signals continued build-out of firming capacity alongside rising renewable generation in Queensland, with the underground connection designed to minimize surface disruption while meeting regulatory requirements for large-scale grid interconnections.

How will Powerlink’s underground link enable AGL’s 500‑MW/2,000‑MWh battery integration?

• Provide a high‑capacity physical pathway: high‑voltage underground cable(s) sized to carry 500 MW export/import between the BESS and the nearest transmission substation, with thermal backfill and duct banks to meet continuous and peak ratings.
  
• Step‑up and interface equipment: battery inverters connect to site transformers (e.g., 33–66 kV to 132/275 kV) feeding GIS/AIS bays; the underground link ties those bays into Powerlink’s transmission node.
  
• Grid code compliance: enables delivery of mandated fault ride‑through, voltage control, and frequency response by integrating protection schemes, synchronizing controls, and testing under Powerlink/AEMO standards.
  
• Protection and control integration: differential/distance protection, cable sheath bonding/earthing, and high‑speed communications (fiber in the cable) link the BESS to SCADA/EMS for real‑time dispatch and curtailment signals.
  
• Reactive power and system strength: cable capacitive effects managed via reactors/STATCOMs; grid‑forming inverter capability coordinated to provide voltage support, synthetic inertia, and system strength where required.
  
• Ancillary services enablement: secure telemetry and metering allow participation in FCAS markets, contingency and regulation services, and potential system restart and network support contracts.
  
• Reliability and resilience: underground alignment reduces exposure to bushfire, wind, and lightning, improving availability for peak‑shaving, evening ramp support, and contingency coverage.
  
• Minimized surface impacts and faster approvals: trenching/HDD under roads and waterways, limited easement widths, and reduced visual impact streamline environmental and planning pathways compared with overhead lines.
  
• Congestion management: a dedicated, short underground spur to a strong bus reduces thermal and stability constraints versus longer radial feeders, improving dispatchability and revenue certainty.
  
• Commissioning pathway: staged energization (cable first, then bays/inverters) allows early network tests, model validation, and market registration ahead of full 500‑MW operation.
  
• Future‑proofing: duct banks and substation bay designs can allow additional circuits or uprating, enabling later capacity expansions or colocated assets without major rework.
  
• Maintenance and outage coordination: link boxes/joint bays and fiber diagnostics support condition monitoring and rapid fault location, reducing downtime and preserving battery cycling value.
  
• Safety and compliance: earthing, induced voltage control, and cable sealing ends at transition structures meet high‑voltage safety requirements for large‑scale storage interconnections.