In South Australia today, rooftop solar on households and businesses combines to be the biggest electricity generator in the State. When left uncontrolled, there have been times when system security was at risk. That's why we’re delivering world-first solutions that actively manage the solar exported to the distribution network.
The Australian Energy Market Operator (AEMO) is responsible for managing the security of supply for the national grid and may direct SA Power Networks to reduce solar exports as a last resort if system security is at risk. This is known as solar curtailment.
What is Solar curtailment?
Solar curtailment is the intentional reduction of solar power generated and exported to the network. It is a last resort after AEMO has used all of its other available levers to maintain system security.
Why do we need solar curtailment?
South Australia leads the world when it comes to the proportion of energy provided by rooftop solar. It's something we strongly endorse and we're well on our way to meeting our goal of doubling the amount of solar we can support on our network by 2025.
As more households install rooftop solar and batteries, and also invest in electric vehicles (EVs), we need to balance the combined energy of this new source of variable energy generated with network operations, the same way we would with any large single generators such as a solar or wind farm.
Our network was built long before solar was even an option and was designed mainly to supply power in one direction: from your substation, to your street transformer, and then to your property. Now, when lots of solar energy is exported back into the network at once and there is low energy demand, some parts can become congested. We see this happen on some mild, sunny days on weekends, when there is a lot of solar energy being generated, but energy-hungry appliances like heating and cooling are not required. This has the potential for local voltages to be pushed high (overvoltage) and in rare cases cause local blackouts.
How is solar curtailment applied?
AEMO monitors grid stability at a national level to manage risks of overloading. For South Australia, stability of the interconnector between us and Victoria is critical to reducing widespread outages. If there’s a risk of instability, we may be directed by AEMO to stabilise the grid.
Curtailment, or limiting of solar exports, is one way we can keep the electricity grid stable and prevent potential wide-spread outages. It’s never the case that we have too much solar or renewable energy, but rather the mix of solar and traditional generation is not optimal for safe and stable grid operation.
In order, the steps we take as the grid operator in these events are:
- Turn off large-scale solar and wind farms.
- Turn off large-scale solar systems such as shopping centres and factories.
- Turn off the exporting of rooftop solar using the regulated Relevant Agent and Dynamic Export functions.
- Turn off any remaining exporting rooftop solar using our Emergency Voltage Management (EVM) function.
Rooftop solar can be curtailed in the following ways
Automatic settings that keep the local area protected
All inverters installed in South Australia are required to comply with certain standards and settings (AS4777.1 and AS477.2). These settings protect the premises, as well as the local network. If voltages start to increase towards the top of the safe operating range, the inverter automatically reduces its generation. We monitor voltages and upgrade street transformers if we measure an issue.
Solar curtailment through signals over the internet as directed by the market operator AEMO
State Government regulation (Smarter Homes) requires all inverters installed after 28 September 2020 to have the ability to be turned off remotely. SA Power Networks may be directed by AEMO to curtail solar in this way during an emergency situation where the stability of the grid is at risk.
Solar curtailment by tripping the inverter though Enhanced Voltage Management (EVM)
We undertook a major project to upgrade voltage management at 139 of our major substations to have more precise control over voltage in the network in these areas.
The upgrade – supporting around 790,000 of South Australia’s 900,000 electricity customers - allows us much smarter management of voltages in the network. In the middle of the day, we can lower voltages allowing more solar generation on the network. At peak times we can raise the voltage to ensure appropriate supply.
EVM can also be used to trip off solar inverters as a last resort when directed by AEMO to actively manage exports to the network.
We have developed this as an interim measure to help manage solar while we implement our world-leading Flexible Exports solution, which will allow eligible customers to export up to 10kW most of the time, and curtail generation for congestion or in an emergency. As more customers adopt Flexible Exports, this will provide a sophisticated system for managing the interaction between each individual customer’s rooftop solar and our network and for manging the security of supply on the grid, also reducing electricity bills by reducing the cost of network upgrades.
How often does solar curtailment happen?
We only act to reduce solar exports at the direction of AEMO. It is a last resort and has rarely been utilised to keep the energy grid stable.
Curtailment of solar exports happens very rarely and in most cases is not noticeable for customers, as all that happens is the customer’s solar system stops exporting for a period of time.
For solar curtailment to be invoked, generally it means the South Australian electricity system has been separated from the national grid (i.e. we have lost transmission connection via the interconnector with Victoria). Completion of Project EnergyConnect with New South Wales will provide additional back-up which will significantly reduce this risk.
Once a year we also test trip the inverter through signals over the internet to make sure that everything is working in case there is an emergency. This typically occurs in the morning or evening in Spring to limit impacts to exports, and lasts less than 1 hour.
Frequently asked questions and answers around solar curtailment
All inverters installed in South Australia are required to comply with certain standards and settings (AS4777.1 and AS477.2). These settings protect the premises, as well as the local network. If voltages start to increase towards the top of the safe operating range, the inverter automatically reduces its generation. SA Power Networks monitors voltages and upgrades street transformers if we measure an issue.
If you find that your inverter is regularly turning off, it is likely for another reason.
This measure will only be used as a last resort when there is a risk to grid stability. It is extremely rare, and should it occur, some people’s solar may need to be curtailed for a few daylight hours on a few days a year.
During a disconnect event, you may be able to power your home if your solar system is set up with the correct islanding capabilities. Islanding capabilities are different from the blackout protection function. You should contact your solar installer to check how your system has been set-up.
During this time, other Distributed Energy Resources (DER) connected to your property such as home battery systems and hot water systems may switch off due to voltage changes.
Other reasons why your inverter may switch off or reduce output
If your inverter switches off or reduces output you may wish to check your Solar Inverter Settings.
Instructions on how to turn off your solar
In very limited circumstances, you may need to turn off your solar or be asked to do so.
Find more information on how to switch off your solar PV system.