Australia’s electricity grid: Over-governed, highly regulated and under-engineered

transmission network with rendered connection points (reactive taiwan)
Image: Shutterstock

Over-governed, highly regulated and under-engineered—that’s Australia’s national electricity grid, writes Phil Kreveld.

The state and territory energy ministers, and the federal energy minister all have their own ideas about what their portion of the grid and what the national grid should look like. They are only in agreement about the national rollout of renewables because it sort of says so in their communique following last year’s gathering of energy ministers, orchestrated by Chris Bowen.

Related article: Renewables and tottering networks

In fact, Victoria doesn’t want gas or coal firming, Queensland sees no problem with either, the commonwealth thinks Kurri Kurri should run its gas turbines on hydrogen—never mind that the technology isn’t there yet. The regulators regulate the minutiae but avoid the big picture and AEMO has the unenviable task of herding the cats so that the grid operates securely and stably. Hidden in AEMO’s latest update of its Integrated Systems Plan is the following:

4.3 Stronger services for power system requirements
Just as the NEM’s generation and dispatchable resources are transforming, so too will the manner in which the power system services needed to keep the NEM secure and reliable are provided. For example, with fewer synchronous generating units, there are fewer sources of system strength, dynamic reactive support, inertia, primary frequency response and frequency control ancillary services that these units have traditionally provided. Likewise, there are fewer options for black restart services and sources.

The highlighted line, added here for emphasis, is the only reference to black (re)start in the entire document. Under-engineering makes for great uncertainty in the restoration of power, should there be more occurrences like the South Australian blackout of 2016. Appropriate engineering would see to the design and regular revision of cranking pathways as more renewables replace gas and coal synchronous generation. Outside-in power restoration, which then revived South Australia, uses the remaining, stable network to resynchronise the blacked-out region.

Inside-out power restoration, whereby an entire grid can be powered up relies on defined cranking pathways. Basically a cranking pathway establishes a generator, or generators when clustered, capable of cold start, and usually a nearby load centre to allow the establishment of a constant voltage and frequency region. From this initial region, other generators can be synchronised to service more load centres.

An extensive grid requires several or more cranking pathways and elaborate resynchronisation to power up, taking as much as day or longer to re-establish a stable grid. Cranking with synchronous generators is well established although it is not a given that we had defined pathways when asynchronous wind, solar and later batteries entered the NEM around the first decade of 21st century.

However, with mainly asynchronous generators it is virgin territory. The German electricity distributor, WEMAG, as early as 2017 trialled battery-based restart successfully but on a very limited scale. There is also trialling in this country of battery-energised voltage forming inverters but notwithstanding these important developments, black start procedures require ‘all-of-grid’ design and testing.

The latter is often enough left to actual black out occurrences! Black start generators require stable energy sources which can be a challenge for batteries given the requirement for inverters to stay on line for more than a few hours. Thermal energy storage can be scaled to provide long term energy and can interface with steam turbine-synchronous generator plant, bypassing creaking, ancient boilers.

Low temperature differential heat sources with Rankine cycle turbines can also be employed but the point is this: integrated, whole-of-grid design is required. Traditional SCADA systems should be paralleled with synchrophasor monitoring. Millisecond response control for grid-following and voltage forming inverters that might be considered for dynamic load centres and cold start generation respectively should be designed and tested under acceptable stability limits. This is a big job and is not being tackled.

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AEMO is not blind to the above but it is not the designer of the grids and its jurisdiction is limited so that achieving an overall design and control paradigm appropriate to 2030 and beyond relies on cumbersome, lengthy procedures involving governments (and politics). Apart from start up, there is the associated first swing stability criterion. The loss of a transmission line can cause loss of stability, with voltage collapse spreading through the grid. Small signal stability is extensively monitored because it relies on a working grid, whereas the loss of first-wing stability can be the initiator of islanding of parts of the NEM grid, as well as blackouts.

It is high time that an overarching engineering voice is heard in the governments of Australia and for the implementation of a national grid design authority.

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