Yesterday, you may have noticed that your solar photovoltaic (PV) system stopped generating or exporting energy for a period - it should have been for less than an hour.

SA Power Networks (SAPN) was testing its capability to curtail solar, which it may be directed to do to help keep the electricity system stable during a system security emergency.  

This once-a-year test is a “fire drill” for the grid and simulates an emergency to check all people and systems are ready to respond for a rare but urgent event. 

The Australian Energy Market Operator monitors grid stability at a national level and will work to maintain system security (balance electricity supply with demand).  

South Australia has more rooftop solar than almost anywhere in the world and occasionally, when rooftop solar exports are very high and demand is very low, that balance can be difficult to strike. SA Power Networks is delivering a range of innovations to overcome this challenge, but still needs to be prepared for unlikely scenarios, such as the interconnector from South Australia to Victoria failing, leaving SA unable to export its surplus solar. 

Ultimately, if AEMO forecast system security is at threat after using all its controls, it will direct SAPN to increase operational electricity demand, and the most effective way to do this is by curtailing solar. If system security is not managed, widespread power outages could occur. 

In 2020, the SA Government passed legislation that required new solar systems to have the ability to be switched off during a system security emergency. This “Smarter Homes” function is what SAPN was testing yesterday. 

Why do you need to test?

If AEMO directs SAPN to increase operational demand, it may have to be done in a moment’s notice.  

SAPN needs to be sure that those solar systems installed after September 2020 are compliant, and that the agents who disconnect/reconnect them (these are third parties knows as “Relevant Agents”) will be responsive.  

If they aren’t confident of that compliance and responsiveness, they will need to plan to use more severe measures during a system security emergency.  

This most recent system test proved the response of agents, and the systems of Smarter Homes continues to improve year-on-year, which means that SAPN can confidently rely on this emergency measure. 

Why is this test a ‘surprise’?  

SAPN had to be certain that this test would deliver accurate results, so it was run like a 'fire drill' to simulate an emergency situation. Solar installers were notified on the morning of the test, and a notice to industry and customers was placed on SAPN’s website. 

Through this approach, SAPN was able to test the ability of Relevant Agents to respond in an emergency and be assured that the response of customers’ systems was both accurate and compliant with the Smarter Homes legislation. 

How did this test impact customers?

About 40,000 solar customers were part of the most recent test. SAPN intentionally chose this day due to the moderate solar efficiency (the output of the rooftop PV). They wanted to minimise the impact on customers. 

Most customers would be unaware of the test. For less than one hour, their rooftop solar PV would have ramped down to 0kW, and then ramped back up again. 

On average, customers would have missed 1.5kWh of solar generation, which is worth $0.09 of export (at 6c/kWh), or $0.83 of consumption offset (at 55c/kWh). These tests are prepared weeks in advance and are based on weather and solar forecasts exactly to minimise these impacts to customers. Additionally, the fog over Adelaide enabled these costs to be very small. 

Part of testing is to also return systems to normal when the emergency has been resolved. For sites that curtailed too slowly (or not at all), or reconnected too slowly, SAPN is working with agents and manufacturers to improve this performance. For a small cost and perhaps some inconvenience to customers, SAPN was able to confirm its reliance on this emergency measure, to help prevent future likelihood of widespread blackouts in a system emergency.  

What next?

 SAPN is focused on contributing to measures which ensure that electricity demand matches supply, as much as is possible and will benefit customers. In the meantime, SAPN must ensure that it maintains the system's robustness and reliability, as SA continues to integrate more renewable energy sources into the network. 

These tests won’t be frequent and SAPN will continue to make all efforts to minimise the cost and inconvenience to customers.

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