Queensland’s North West Power System and CopperString 2032

Client: North West Power System Working Committee
Location: Queensland, Australia
Date: 2023

Providing technical guidance, regulatory guidance and power system modelling to prepare for connection of an isolated grid

Background

The CopperString 2032 project (formerly known as CopperString 2.0) involves approximately 1,000 km of high-voltage electricity transmission line connecting Townsville to Mount Isa and connecting Queensland’s North West Minerals Province (NWMP) to the National Electricity Market (NEM). The 375,000 km² NWMP is a treasure trove of critical minerals, which will be crucial for producing the low-emissions technologies that will drive Australia’s clean energy transition. CopperString will connect the NWMP into one of the largest renewable energy zones in Australia (the proposed Flinders REZ in North Queensland).

The CopperString project will underpin the new Queensland SuperGrid transmission backbone and is the largest expansion to the power grid in Australia.

However, a project of this nature requires careful planning on many fronts, including to ensure that the North West Power System (NWPS) can remain stable and reliable as the only large thermal power station is potentially displaced and the proportion of solar and wind generation grows very rapidly. The power system must have adequate energy when needed, enough frequency control, inertia and voltage control, and the ability to be restored successfully after outages.

Solution

Entura’s long relationship with the NWPS Major Users Group and deep understanding of the Mount Isa/NWPS, developed over many years, positioned us well to prepare a whitepaper describing how the ~300 MW network could be operated during the transition to CopperString and beyond.

Our role was technically challenging, given that the isolated power system is neither a traditional off-grid mining system nor a traditional grid, and there are few precedents of how power systems of this size (approximately 10 times larger than the average off-grid project, but only about 1% of the size of the national grid) can transition to a greater proportion of renewable energy generation. A key question was whether or not the latest grid-forming inverter technology will perform as hoped and unlock the full capacity of such a grid.

We completed a number of projects to update and verify the Mount Isa power system model ready for possible inclusion into the NEM model. These include:

  • a black start study to determine an appropriate procedure to restart the power system if it goes black
  • a ‘red flags’ study to determine if it is feasible to connect a new solar farm and battery
  • reviews of the model against basic generator and transmission system data to confirm and improve model accuracy
  • review of the reports provided by the CopperString project from the perspective of the NWPS Major Users Group, with recommendations to maximise the reliability of supply to Mt Isa and the NWPS.

These projects built on previous studies we’d conducted on this power system to enable the connection of 240 MW of new combined-cycle gas-fired generation and a 60 MW backup simple-cycle station (Diamantina and Leichhardt power stations). Studies included load flow, fault levels, critical clearing times and analysis of the centralised predictive load-shedding scheme. When it became necessary to decommission a main substation and subsequently recommission it, we studied the system for several system topologies.

We created the first PSCAD model for this network and are now the custodian for that model along with a PowerFactory harmonic model for the network (prepared by others). Following from previous work completed for this client, we have remained the custodian of the Mount Isa PSSe power system model.

Entura also completed separate studies for a number of connection proponents in the region, including the proposed Sybella Creek project, the Thompson and Georgina power stations, the Dugald River Solar Farm, and connection of a new 30 MW mining operation onto the 220 kV portion of the system.

We have also prepared generator performance templates for the connection of new generation, provided advice on how they might be included into the regulatory framework, and provided general advice on power system events. On one occasion, this was in real time while the system was black.

OUTCOME

With Entura’s support, the NWPS system operator now has protocols in place for managing the power system at the renewable penetrations expected in the short term. Protocols are being developed through the whitepaper process to manage the power system until CopperString connects. After CopperString connects, it is expected that all generation will join the NEM and power system operation will become more routine; however, the NWPS users are determined to be prepared for the possibility of needing to operate the NWPS longer and with higher renewable penetration if the CopperString connection is delayed.

CopperString 2032 broke ground in mid-2024 and is on track for completion by 2029, with operation expected by 2031.