When cheap solar is expensive
Badly installed solar PV makes Australia’s grid fragile
On August 25 last year there was nearly a system blackout when, improbably, three states of Australia were islanded by one lightning strike. Within seconds, trips were switching, two smelters were load shed to save the grid from collapse, and across the Eastern Seaboard of Australia frequency and voltages surged or fell everywhere. In Sydney 45,000 homes lost power for a couple of hours. Shops had to close. Trains were stopped. Passengers were stranded. Traffic signals were not working on major roads. There was chaos. Industrial users shut down in a mass of 725MW of load shedding.
The AEMO final report on that day has just come out and shows us just how fragile our grid is. This was not so much a freak accident, as an accident waiting to happen.
It turns out that another cost of cheap rushed solar panels is that many drop out with voltage spikes, suddenly going offline and leaving another hole to fill. The numbers are amazing — of panels installed in the last 2 years as many as one-third in South Australia dropped out when we needed them and about 1 in 6 failed in Queensland.
If smelters are offline, hundreds of thousands of dollars are burning, and millions is at risk…
Obviously the true costs of installing solar panels properly are higher than advertised. When we add up the lifetime cost of solar does it include loss of earnings of unrelated businesses?
August outages underline risks to the reliability of the national grid
Perry Williams, The Australian
The Australian Energy Market Operator said several generators failed to respond as expected including “counter-productive responses” that could have been limited or prevented if sufficient frequency control settings were enabled in each region.
While Tesla’s giant battery was praised for helping to stabilise frequency, four unnamed wind farms in South Australia reduced their output to zero because of incorrect settings while solar rooftop systems also crashed out and were unable to assist in boosting supply to either Victoria or NSW.
AEMO detailed how 15 per cent of sampled solar systems installed before October 2016 dropped out during the event. Of those installed after that date, nearly a third in South Australia and 15 per cent in Queensland failed to meet standards.
Crash Test Dummies are here
Australia’s shift to renewables is ramping up:
The rapid switch to renewables is having a profound impact on the grid, with solar generation jumping by 38 per cent in the three months to September while wind grew by 16 per cent, displacing gas from the grid’s power mix.
This event demonstrates the extent of the decline in system resilience, and its correlation with the reduction of continuous primary frequency control over the past several years. Restoring primary frequency control is essential to reversing the decline in resilience. AEMO considers that action to address the resulting risks is required as soon as possible, recognising that a longer-term mechanism to appropriately incentivise the provision of primary frequency control is necessary, but will take some time to develop.
We didn’t need to worry much about frequency stabililty back when the grid didn’t have so many renewables.
I found these conclusions interesting: (p86)
- There was a delay in synchronising the QLD and NSW networks due to the lack of frequency control available in QLD.
There was not even enough synchronous power in Queensland to enable people to reconnect the two states.
- The power system in QLD was not in a secure operating state for the entire 68-minute period of separation from NSW. While AEMO took all reasonable steps to return the power system to a secure operating state, during this period AEMO could not procure enough contingency raise FCAS to cover the loss of the largest generator (Kogan Creek) or contingency lower FCAS to cover the loss of the largest load (Boyne Island smelter) from within QLD. Re-connecting QLD with NSW enabled the FCAS requirements for QLD to be met from other regions. The actions taken by AEMO were appropriate and in accordance with the NER and published procedures.
- This event saw a loss of supply into the VIC/NSW/TAS region of the NEM of 1,030 MW, resulting in 997.3 MW of uncontracted load interruption.
Electricity nerds may like to read the gory details of how the faults unfolded:
Events of 25 August 2018 On Saturday 25 August 2018, there was a single lightning strike on a transmission tower structure supporting the two circuits of the 330 kilovolt (kV) Queensland – New South Wales interconnector (QNI) lines. The lightning strike triggered a series of reactions creating faults on each of the two circuits of QNI at 13:11:39. The QLD and NSW power systems then lost synchronism, islanding the QLD region two seconds later, at 13:11:41.
At the time, 870 MW of power was flowing from QLD to NSW. QLD experienced an immediate supply surplus, resulting in a rise in frequency to 50.9 Hertz (Hz). The remainder of the NEM experienced a supply deficit, resulting in a reduction in frequency.
In response to the reduction in frequency in the remaining interconnected regions:
- The frequency controller on the Basslink interconnector immediately increased flow from TAS to VIC from 500 MW up to 630 MW. This created a supply deficit in TAS, causing the disconnection of 81 MW of contracted interruptible load under the automatic under-frequency load shedding scheme (AUFLS2) to rebalance the TAS power system at 13:11:46.
- The SA–VIC interconnector at Heywood experienced rapid changes in power system conditions that triggered the Emergency APD Portland Tripping (EAPT) scheme. The scheme responded to those conditions, as designed, to separate the SA region at Heywood. This occurred some 6 seconds after the QNI separation at 13:11:47.
At the time of separation at Heywood, SA was exporting power to VIC. This meant there was a supply surplus in SA immediately after separation, causing frequency to rise. In the remaining VIC/NSW island, the resulting supply deficit caused frequency to fall below 49 Hz, triggering under-frequency load shedding (UFLS) to rebalance supply and demand across those regions. A total of 997.3 MW of supply was interrupted in VIC and NSW, comprising 904 MW of smelter load in both regions and 93.3 MW of consumer load in NSW.
The SA-VIC interconnection was restored at 13:35 on 25 August 2018, and QNI at 14:20. The interrupted TAS load commenced restoration at 13:40 and the NSW and VIC smelters were permitted to reconnect at 13:33 and 13:38 respectively. All NSW consumer load was restored by 15:28.
This event created three separate frequency islands on the mainland NEM and highlights the present challenges of controlling frequency in the NEM, and the potential consequences of the reduction of primary frequency control over a number of years.