Solar Curtailment in South Australia: Why Your Output Was Cut

Key Takeaways

• Solar curtailment is an intentional reduction of your system's output by SA Power Networks to maintain grid stability.
• Your solar system may stop generating or exporting during the annual Smarter Homes Solar Curtailment Test, a scheduled grid "fire drill".
• All solar inverters installed in South Australia after September 2020 are required to be remotely controllable for curtailment.
• If your system stops generating outside of a scheduled test, or doesn't resume normal operation, contact your accredited solar installer.

Your Solar System Stopped Generating in South Australia

If your solar photovoltaic (PV) system in South Australia suddenly stopped generating or exporting power, it might not be a fault. SA Power Networks, the electricity distribution network manager for South Australia, can intentionally reduce solar power generation and export. This process is called solar curtailment.

One common reason for this temporary shutdown is the annual Smarter Homes Solar Curtailment Test. This scheduled event is a "fire drill for the grid" designed to ensure the network can manage high solar penetration safely. If you are outside South Australia, your local electricity distributor sets its own rules; you can find their name on your electricity bill.

What Is Actually Going On: Grid Stability and Curtailment

South Australia has a high level of rooftop solar adoption. While beneficial, this can sometimes lead to situations where the amount of solar energy being exported back into the network exceeds local demand. When lots of solar energy is exported back into the network when there is low energy demand, there may not be anywhere for the electricity generated to be consumed. This mismatch between supply and demand can trigger unplanned outages.

To prevent these outages and maintain network stability, SA Power Networks may curtail solar exports. This action is often directed by the independent Australian Energy Market Operator (AEMO) as a last resort if the electricity network is at risk of becoming unstable.

As of September 2020, all solar inverters installed in South Australia were required to have the ability to be turned off remotely. This capability allows SA Power Networks to manage energy flows effectively.

The Curtailment Process

When AEMO directs SA Power Networks to curtail solar exports, a series of steps may be taken:

1. Large-scale generation first: Large-scale solar and wind farms are turned off.
2. Commercial solar: Large-scale solar systems, such as those on shopping centres and factories, are turned off.
3. Home rooftop solar (managed): The exporting or generation of home rooftop solar is turned off using regulated Relevant Agent and Dynamic Export functions.
4. Home rooftop solar (emergency): Any remaining rooftop solar is turned off by causing systems to trip off using Emergency Voltage Management (EVM) functions.

Customers are unlikely to notice if their solar is curtailed, as the process is designed to be seamless.

The Annual Smarter Homes Solar Curtailment Test

SA Power Networks conducts an annual test of its ability to temporarily curtail rooftop solar generation. This exercise simulates a rare but urgent situation to confirm that all systems and people are ready to respond if an actual emergency occurs. It is like a fire drill for the grid.

During this test, your solar PV system may stop generating or exporting energy for a short time, usually an hour or less. For example, a test might be scheduled for a specific Tuesday in August.

What Happens During the Test

• Systems tested: Solar systems installed after September 2020 are checked for compliance during this annual test.
• Energy impact: On average, customers will miss about 1.5 kWh of generation during the annual test.
• Follow-up: For any systems that curtail or reconnect too slowly, or not at all, SA Power Networks works with agents and manufacturers to improve performance.

If your system stopped generating on a day when SA Power Networks announced its annual test, this is the most likely explanation.

What You Can Check Yourself, and What You Cannot

If your solar system has stopped generating, especially on a day when an annual curtailment test is known to occur, there is usually nothing you need to do. The system should automatically resume normal operation once the curtailment period ends.

What you can check yourself:

• Check for announcements: Look for official announcements from SA Power Networks regarding scheduled curtailment tests. These are usually communicated in advance.
• Inverter display: Check your inverter's display for any error codes or messages. If it shows a "grid disconnected" or "waiting for grid" message, it might indicate a temporary grid issue or curtailment.
• System status: Most modern solar systems have online monitoring. Check your system's app or web portal to see its current status and generation history. This can confirm if generation dropped to zero and then resumed.

What you cannot check yourself (and requires an accredited installer):

• Changing inverter settings: Grid-protection settings on your inverter are configured by an accredited installer according to AS/NZS 4777.2 and your connection agreement. You must not attempt to change these settings yourself. Incorrect settings can compromise grid stability and safety, and may void your warranty or connection agreement.
• Internal inverter faults: If your inverter displays a specific fault code that persists after a known curtailment event, or if it fails to restart, it may indicate an internal issue.
• Wiring or component issues: Any physical inspection or repair of solar panels, wiring, or the inverter requires a licensed electrician or accredited solar installer.

If your system does not resume normal operation after a known curtailment event, or if it stops generating unexpectedly at other times, contact your original solar installer or another accredited solar professional. They can diagnose the issue safely and correctly.

What the Published Sources Do Not Tell You

While SA Power Networks provides clear information on solar curtailment and the annual test, some specific details are not publicly available:

• Exact voltage trip thresholds: The precise voltage limits at which inverters are required to trip off the grid are set out in AS/NZS 4777.2. This is a paid standard, and the specific numerical thresholds are not published by SA Power Networks or generally available to the public. Your installer or inverter distributor can confirm what is configured on your specific inverter model.
• Specific test dates: While the annual test is a regular event, the exact date and time for each year's test are announced by SA Power Networks closer to the event, rather than being published years in advance.
• Detailed non-compliance follow-up: SA Power Networks states it works with agents and manufacturers for systems that don't perform as expected during the test. However, the specific processes, timelines, or penalties for non-compliant systems are not detailed in public documents.
• Network rules in other states: The rules and mechanisms for solar curtailment are specific to SA Power Networks in South Australia. Other Australian electricity distributors, such as those in Victoria, New South Wales, Queensland, or Western Australia, have their own distinct rules and operational procedures for managing solar exports and grid stability. Always check with your local distributor for rules applicable to your area.