Powerlink’s big bet: CopperString and the north-west minerals grid

1,100 kilometres of new high-voltage line between the Queensland coastal grid and Mount Isa is not a project you sneak past the regulator. It’s the single biggest build Powerlink Queensland has taken on since the company existed, and it carries a name that sounds more like a board game than critical infrastructure: CopperString 2032. I’ve been tracking this one since the Palaszczuk government first folded it back into state hands, and the project has a habit of moving the finish line every time someone asks a hard question about cost.

Powerlink is wholly government-owned, which makes it an unusual beast next to the privatised transmission businesses in Victoria and South Australia. It runs the high-voltage backbone across Queensland: the 275kV and 500kV spine that gets bulk power from generators to the distribution networks, and it answers, ultimately, to the state Treasurer rather than to shareholders chasing a return. That ownership structure matters for how CopperString gets built and who wears the risk if the economics wobble.

What CopperString actually is #

Strip away the branding and CopperString 2032 is a transmission line connecting the existing Queensland grid, which currently stops well short of the north-west, through to Mount Isa and the minerals province around it. That region holds copper, zinc, lead and a swag of critical minerals prospects that currently run on isolated diesel and gas generation, because there’s never been a wire long enough to reach them from the coast.

The pitch is straightforward: connect the north-west to the National Electricity Market, let mining and processing operations switch from diesel to grid power (increasingly renewable as Queensland’s wind and solar build-out continues), and open up transmission access for wind and solar projects in a part of the state that currently has none. Powerlink’s own project materials describe staged construction running through the back half of this decade, with energisation targeted around 2032 – hence the name. Readers who want the full build and cost history can see our earlier look at CopperString 2032: Queensland’s long bet on the north-west, which goes into the project’s tortured ownership history in more detail than I’ll repeat here.

A project that changed hands more than once #

CopperString has been “nearly happening” for the better part of fifteen years. It started as a private proposal, bounced between developers, picked up Commonwealth and state funding commitments, and was eventually brought inside Powerlink’s own balance sheet so the state-owned transmission business would build, own and operate it directly rather than relying on a private proponent to raise the capital. That’s a meaningful shift. It puts the project’s financing risk on the Queensland government’s books rather than a developer’s, and it means Powerlink’s regulated asset base, the pool of assets the AER allows it to earn a return on, will eventually carry the cost once the line is in service.

Let’s be careful with that number, because “cost of CopperString” has been quoted at wildly different figures depending on which year and which scope you’re reading. Early private proposals put the line in the low billions. Powerlink’s own staged cost estimates, as the scope expanded to include higher-capacity sections and more substations, have climbed well past that. The company’s public statements describe a project cost in the several-billion-dollar range, with Commonwealth equity and concessional debt support layered in alongside state funding. I’d treat any single headline figure with some scepticism until the final investment decision on the last stage is locked and the AER has had its say on how much flows into regulated charges.

The transmission-for-minerals argument #

The case for CopperString rests on a bet about what the north-west minerals province becomes over the next decade. Australia’s critical minerals ambitions, the ones that show up in federal strategy documents and in the Safeguard Mechanism’s industrial decarbonisation push, depend on processing happening onshore rather than shipping raw ore overseas. Processing needs reliable, reasonably cheap power at scale, and diesel generation at remote mine sites is neither of those things once you’re running continuous operations.

If the minerals boom in the north-west actually arrives at the scale proponents describe, a grid connection pays for itself through decades of transmission use-of-system charges from mining and processing load. If it doesn’t – if copper and critical minerals prices soften, or projects slip the way resource projects often do – Powerlink is left with a very long, very expensive line serving a smaller customer base than the business case assumed. That’s the central risk, and it’s not a hypothetical one. Queensland has watched resource booms promise more than they delivered before.

Where Powerlink sits in the transition more broadly #

CopperString is the headline project, but it’s not the only thing on Powerlink’s books. The company is also the host transmission network for Queensland’s Renewable Energy Zones, and it’s a counterparty in the broader conversation about who pays for the transmission expansion AEMO’s Integrated System Plan says the National Electricity Market needs. Readers following that debate statewide might find our piece on who really pays for the transmission build-out useful background, because Powerlink’s regulated revenue model is a live example of the mechanism in practice: build the asset, get it into the regulated asset base, recover the cost from network users over decades.

Powerlink also sits adjacent to Queensland’s pumped hydro ambitions. The Borumba project, which Queensland Hydro is developing as a roughly 2GW pumped storage scheme, will need transmission capacity to actually move that power where it’s needed, and Powerlink is part of planning for that connection. We’ve covered the pumped hydro side of that story in Borumba pumped hydro: where Queensland’s 2GW bet actually stands, and the two projects are worth reading together: a state government building generation, storage and transmission simultaneously is a genuinely different model to the private-developer approach dominant in New South Wales and Victoria.

Comparing the public ownership model #

It’s worth sitting with what public ownership actually buys Queensland here, because the comparison with privately-owned transmission elsewhere in the NEM isn’t straightforward. A private transmission developer has to convince debt and equity markets the project clears a commercial hurdle rate before it breaks ground. Powerlink, backed by the state balance sheet, can proceed on a slower-burn industrial policy rationale that a private proponent probably couldn’t justify to its board. That’s not automatically a point in favour of public ownership. It just means the risk calculus is different, and the taxpayer (via the state budget) and the network customer (via regulated charges) are the ones absorbing a bet that private capital judged too marginal for too long. I’ve gone deeper on that trade-off in public versus private ownership of generation: who builds it better, which looks at generation rather than transmission, but the underlying tension about who carries project risk is the same.

The regulatory mechanics that decide who pays #

Powerlink’s revenue is set through the AER’s regulatory determination process, the same framework that governs every other transmission network service provider in the NEM. The AER reviews Powerlink’s proposed capital expenditure, sets an allowed rate of return, and that combination determines what flows through to Queensland’s transmission use-of-system charges: ultimately a line item that shows up, diffused across millions of customers, on retail bills. CopperString’s capital cost, once it’s operational, becomes part of that regulated asset base, though the exact treatment of Commonwealth and state contributions (equity versus grant funding) affects how much of the bill customers actually wear versus taxpayers. The AER publishes the detail of these determinations on its own site, and it’s worth a look if you want the mechanics rather than the summary (see the AER’s network revenue determinations at aer.gov.au).

AEMO’s Integrated System Plan has consistently flagged northern Queensland transmission as part of the broader national build-out needed to connect remote renewable resource areas to load, and Powerlink’s own transmission annual planning report cross-references that work. For readers who want the national framing rather than the state-specific one, our explainer on what the AEMO Integrated System Plan actually says sets out how projects like CopperString fit the wider national picture of where new wires are judged most valuable.

My honest read on the timeline #

I reckon 2032 is a defensible planning target, not a promise anyone should bank a mining investment decision on. Transmission projects of this scale in Australia have a well-documented habit of slipping: land access negotiations, environmental approvals, supply chain bottlenecks for the steel and conductor that go into a line this long, and construction workforce competition with every other REZ project running concurrently across the eastern states. Powerlink has an easier job than a private developer in one sense: it doesn’t need to re-raise capital market confidence every time a milestone slips. But that comfort can cut the other way too, removing some of the discipline a commercial financier would otherwise impose on scope and cost control. I don’t think that’s a reason to abandon the project. I do think it’s a reason for Queenslanders to watch the AER’s periodic cost reviews closely rather than taking the 2032 energisation date as settled.

There’s a chess analogy I keep coming back to with projects like this: the opening moves look obviously correct, almost forced, but the middle game is where resources get committed that are hard to walk back from. Powerlink is several moves into the middle game on CopperString now. The pieces are mostly on the board. What’s left to watch is whether the minerals province delivers the demand growth the business case assumes, and whether Queensland’s budget, and its electricity customers – end up carrying more of that bet than the glossy renders ever suggested.

– Anjali Rao, Grid & Storage Correspondent

Photo by Art Wall - Kittenprint on Unsplash