Intermittent: Another big coal unit trips – that’s four in a week

A 700MW unit at the Eraring coal fired power station in New South Wales tripped on Monday afternoon, taking to four the number of big coal units that have failed without warning in less than a week.

The failure of the Eraring unit at 6pm on Monday follows unexpected trips at of a 420MW unit at Milmerran in Queensland on Tuesday, a 700MW unit at Mt Piper in NSW on Wednesday, and a 560MW unit at Loy Yang A (unit 3) in Victoria on Thursday.

The Mt Piper unit remains out of service, due to tube leaks, along with a 420MW unit at Liddell (out for six months due to turbine blade issues), and lingering problems at another 560MW unit (Unit 1) at Loy Yang A, which has been out for more than a month since tripping in early November.

It means that, aside from the unexpected trips, the equivalent of another Hazlewood power plant (more in fact) is out of service and unavailable as the summer heat intensifies.

The intermittent and unreliable nature of the coal fired power stations will be of particular concern to the Australian Energy Market Operator, charged with keeping the lights on and hoping it has enough reserve capacity to deal with failing coal and gas units.

AEMO last week issued a market notice pleading for operators to check their equipment and make sure it was in a good operational state and able to deliver something close to its rated capacity.

It is worried of a repeat of the events in NSW last February, when with two of four units at Liddell sidelined (840MW), the two biggest gas generators (more than 1,100MW) failed and a widespread blackout was only narrowly averted.

AEMO can predict with a large degree of accuracy any swings in output from wind and solar, but has made it clear that supply is most threatened by unexpected outages from a large thermal unit.

This week, a task-force commissioned by the NSW government after that February near miss warned of a potential “system black” in NSW and noted the lack of preparedness for such an event.

That conclusion is ironic because the NSW grid, sourcing some 88 per cent of its supply from coal fired generation in 2016/17 has the highest reliance on coal of any grid in the world.

The NSW task-force recommended a focus on new technologies, particularly distributed energy – local solar and other renewables and storage – to make the grid more resilient.

The Loy Yang A unit trip last week prompted a remarkable intervention by the Tesla big battery in South Australia, which injected enough power to arrest a fall in frequency caused by the outage, even before big coal generators contracted to provide that service had reacted.

Although expected, the demonstration of its fast response capabilitiy is expected to increase pressure on market rule-makers to accelerate changes that encourage such technologies.

The rules currently are tilted in favour of ageing, incumbent technology, largely because the principal rule maker has failed to perceive an issue and has been slow to respond to new developments.