The widespread uptake of rooftop solar photovoltaic (PV) means that demand for electricity from the grid is falling, particularly in the middle of the day.

Whilst increased levels of solar power helps to reduce carbon emissions and customer power bills, it is also important that the network operators - the Australian Energy Market Operator (AEMO), Powerlink Queensland, and Energex and Ergon Energy Network – can maintain a balance of supply and demand for electricity.

Therefore, the Queensland Government requested us to introduce an emergency backstop mechanism for Inverter Energy Systems (IES). The emergency backstop mechanism is only operated by electricity network operators in an emergency under the direction of the AEMO to help maintain a safe and secure network.

The emergency backstop mechanism is effective in Queensland from 6 February 2023.

Please note: The requirement to install a GSD applies to all applicable IES connection offers that are accepted, or connection contracts entered into, on or from 6 February 2023, regardless of when the connection application is submitted or connection offer was issued.

The emergency backstop mechanism is only applicable in areas where we have AFLC available for signalling.

As a general guide, Ergon Energy Network’s isolated communities, Single Wire Earth Return (SWER) network and some other fringe of grid areas do not have AFLC capability. We have developed a NMI Check search form so you can determine if a site has AFLC capability or not.

In addition, when submitting connection applications via the Electrical Partners Portal, a pop-up message will appear as a guide when an application triggers the requirement to install a GSD.

For IES connections that must comply, the emergency backstop mechanism involves:

1. Device installation - the installation of a Generation Signalling Device (GSD). Sites with multi-inverters have the option to use a single GSD connected to a Demand Response Controller
2. Device signalling - the GSD uses a signal sent over the power line, known as Audio Frequency Load Control (AFLC), to activate the demand response mode ‘DRM 0’ (in an AS/NZS 4777.2 compliant inverter). The ‘DRM 0’ setting is a mandatory capability of inverters under Australian Standards
3. Inverter disconnection - when 'DRM 0' is signalled, the inverter will operate a disconnection device in the inverter
4. All generation stops - the inverter will shut down, ceasing all generation including for self-consumption solar power at the site
5. Inverter reconnection - when the emergency is over, the inverter is sent a signal to reconnect to the network.

As a fail-safe, if an inverter does not receive a signal within 4 hours, the 'DRM 0' setting is designed to automatically reset and allow the inverter to reconnect to the network.

The GSD is a demand response enabled device compatible with Australian Standard AS/NZS 4755.1 Demand response capabilities and supporting technologies for electrical products.

The emergency backstop mechanism will only be operated by network operators under the direction of AEMO to help maintain a safe and secure network.

This will only occur in response to specific network emergency conditions, such as when the main electricity connection between Queensland and the rest of the National Electricity Market (NEM) is offline at the same time as periods of high levels of distributed generation, like solar PV, being exported to the grid.

Queensland has separated from the NEM five times in the last 10 years, with connectivity typically restored within a short period of time.

On the rare occasion that an electricity network emergency event occurs and AEMO issues a direction under its market notices framework:

• A signal will be issued by network operators which will tell the inverters to disconnect from the network
• When advised that the electricity network has been restored to a state where it will remain secure with reconnection of the impacted inverters, network operators will send a signal to the inverters to allow them to reconnect to the network.

As a fail-safe, if an inverter does not receive a signal within 4 hours, the 'DRM 0' setting is designed to automatically reset and allow the inverter to reconnect to the network.

Sites with an existing connection approval (being an accepted or executed offer prior to 6 February 2023) are not required to install a GSD. If a connection agreement lapses or terminates, any new connection application and offer will be based on the Connection Standard that applies at that time.

The requirement to install a GSD applies to all applicable connection offers accepted, or executed, on or from 6 February 2023, regardless of when the connection application was submitted or the connection offer was issued.

Please be aware that we can not make any assurances regarding processing times outside what is provided for under the energy laws.

Any relevant applications that have not received a connection offer, or the offer has been issued but not accepted or executed before 6 February 2023, must comply with the requirement to install a GSD.

The emergency backstop mechanism applies to all new, replacement and upgraded IES applications connected to the low voltage electricity distribution network with a total inverter capacity of 10kVA or above.

Please be aware that the requirement to install a GSD applies to all applicable IES connection offers that are accepted, or connection contracts entered into, on or from 6 February 2023, regardless of when the connection application was submitted or connection offer was provided.

More specifically, emergency backstop mechanism applies to:

• Any new IES connections with an total installed nameplate inverter capacity of 10kVA or above
• Any replacement inverter not under warranty, where the total installed inverter capacity is 10kVA or above
• When adding IES capacity to an existing system and this results in the total inverter capacity being 10kVA or above, all the new inverters being added (regardless of their size/capacity) must be compliant with our current standards and have a GSD. All pre-existing IES approved for install from 6 February 2023, that did not meet the threshold at the time, must also have a GSD added
• Where an integrated IES consists of both energy storage and solar PV sources (otherwise known as a hybrid inverter) where the above conditions are also in place.

The requirement applies equally to systems that are approved for full export, partial export, or nil export.

The emergency backstop mechanism does not apply to:

• Warranty replacements (i.e. ‘like for like’ with the same make and model)
• High voltage electricity distribution network connections
• The limited service areas where our AFLC signalling for the emergency backstop mechanism is currently not available (mainly some remote and fringe of grid areas)
• Where the IES is only for the purpose of an energy storage system (commonly referred to as, AC coupled batteries) and there are no other energy sources (such as rooftop solar PV) connected to the inverter.

Where an inverter or inverters are being replaced, not under warranty, and the total installed inverter capacity is 10kVA or above, the replacement inverters require a GSD.

For example:

• Where a 10kVA IES has a single 10kVA inverter which is being replaced (on or after 6 February 2023), it must be replaced with an inverter that is compliant with the current standards and fitted with a GSD
• Where a customer has a 10kVA IES that has 2 x 5kVA inverters but only replaces one of the inverters with a new 5kVA inverter, the replacement 5kVA inverter must be compliant with the current standards and fitted with a GSD. The inverter which is not being replaced is not required to have a GSD fitted where the installation contract was accepted or executed before 6 February 2023.

Yes, once the total capacity exceeds 10kVA, any inverter covered by a contract that was accepted from the 6 February 2023 is required to meet the requirements for installing a GSD.

The first 5kVA IES does not require a GSD to be installed at the time of the initial installation as it is below the 10kVA threshold. However, when the additional 5kVa IES is installed, this brings the total system size approved to be installed after 6 February 2023 to 10kVA, and therefore a GSD is required to be installed to both IES.

To be clear, the emergency backstop mechanism only applies to IES approved for installation after 6 February 2023 – any IES approved for installation prior to 6 February does not require a GSD.

Yes, the Emergency Backstop Mechanism requires applicable inverters to disconnect from the electricity network, including zero export systems. It is not associated with export to the grid, but rather connection to the grid.

No. Under our Connection Standards, for example STWN1170 Standard for Small IES Connections, Electricity Vehicle Supply Equipment (EVSE) is considered as an energy storage system and therefore excluded from the need to install a GSD.

Yes, our Emergency Backstop Mechanism Factsheet (PDF 618.0 kb) provides general information on the background and operation of the initiative, and how it may impact customers installing new or replacement IES.

When the signal is sent to the GSD, the inverter will shut down, ceasing all electricity generation including any electricity for self-consumption. This will not interrupt the electricity supply to your premises from the grid.

Your electricity consumption during the event will be charged as per your electricity tariff. The impact on your bill from the solar generation ceasing will be similar to your solar system having reduced output on a heavily overcast / rainy day. When the emergency event is over, a signal will be sent to the inverter which will return it to normal operation.

The GSD is part of the equipment that makes up your solar PV installation. Should you experience any issues with the GSD or any other component of your installation, you should follow the instructions or warranties provided to you by your installer. If your installer identifies an issue with the GSD itself, then the installer should contact the manufacturer of that GSD for further support.

Currently there is a single supplier of GSDs, as listed on our Approved Generation Signalling Devices register (PDF 203.4 kb). GSDs can be purchased through Queensland based supplier TMAC (Thew & McCann Group) or electrical wholesalers.

The GSD manufacturer has provided an indicative cost of around $75 when purchased direct (minimum quantities apply), or around $90 when purchased through retail outlets. We are not involved in the setting of prices for GSDs.

Other manufacturers of GSDs may enter the market in the future, subject to those devices meeting appropriate technical specifications, which are available on request by emailing:

• For south east Queensland - tech.enquiries@energex.com.au
• For regional Queensland - tech.enquiries@ergon.com.au

The GSD utilises the existing connection available for the demand response mode function – this is via an external port or internal terminal block, depending on the make and model of the inverter.

For technical requirements and general guidance on installing the GSD, please refer to section 8.10.2 Emergency Backstop Mechanism of the Queensland Electricity Connection Manual (PDF 19.8 mb).

For installation of the GSD:

• Connection may vary depending on inverter manufacturer but is typically via the RJ45 port or 8 pin round communications port or internal terminal block
• In some cases, the settings in the inverter may also need to be configured to ensure it is enabled for 'DRM 0' mode
• The GSD manufacturer(s) will provide generic instructions on installation of the device. We are aware that previously printed versions of the manufacturer’s instructions may differ from the QECM supplement in relation to where the GSD can be mounted and the requirement to have a GSD for each inverter. Where there is a difference, the QECM Supplement should be followed
• Inverter manufacturers may also provide model specific instructions for connection and activation of the 'DRM 0' function, with some inverters requiring an extra module to be purchased to enable 'DRM 0' mode.

The GSD should be installed at the main switchboard and should share the same protection device as the inverter. Where an inverter is located far away from the main switch, connect the GSD at the main switchboard and extend the communication cable to the inverter. Where an inverter circuit originates from a sub-board, the GSD should share the same protection device as the inverter.

No. The GSD is not a network device, it is part of the customer installation.

When the Demand Response Mode (DRM) 0 has been activated

As soon as the grid supply is off (and the power supply to the GSD is interrupted), the GSD will release the DRM0 in the inverter. Once DRM0 is released, if the inverter has energy storage connected, the inverter will be able to offer the same outcome (back-up power) to the customer as it is capable during a network outage.

When the local grid supply is re-instated and the GSD receives power supply, it will go into the same DRM state it was before the power interruption i.e. DRM0 in this case. If the network event is over, a signal will be sent to re-instate the inverter to normal operation.

When power supply to the GSD is interrupted during normal operation

Where power supply to the GSD is interrupted by a grid supply outage, when the inverter is not in any DRM0 mode, there will be no additional impact on the inverter as the inverter will cease operation under the standard anti-islanding function built into all inverters. When grid supply is restored, the inverter will return to normal operation.

The GSD only needs to connect to a single phase from the three phase protection device for the inverter. The inverter will only have a single DRM port which the GSD will connect to.

The commissioning check should ensure the correct and safe installation of the GSD in compliance with the DNSP standards and manufacturer instructions. Where the GSD has been installed correctly and the inverter configured correctly:

• The removal of the RJ45 plug from the DRM mode port on the inverter, or disconnection of the GSD from the terminal block, will trigger the DRM 0 functionality to cease generation as per clause 3.2.2 (d) of AS/NZS 4777.2
• Another option to check that the DRM 0 mode has been configured correctly is to use a test module as described in Appendix D in AS/NZS 4755.1.

Yes, we will be inspecting customer premises to ensure that the GSD has been installed correctly. We'll write to the customer if the inspection identifies that the GSD has not been installed correctly. The customer will then have an opportunity to rectify the non-compliant GSD installation.

Failure to rectify the non-compliant GSD installation may result in the customer’s embedded generating unit being de-energised or disconnected from our electricity network, in accordance with their connection contract.

No. Part of the process for applying for a >30kVA system requires both an RPEQ design and compliance report. These reports will require indication of compliance with the Emergency Backstop requirements. There is no RPEQ compliance report requirement for <30kVA systems.

Evidence of design and commissioning compliance may be requested where concern around a non-compliance is identified.

The emergency backstop mechanism requirements are included in Connection Standards STNW1170 (PDF 669.7 kb), STNW1174 (PDF 2.0 mb), STNW3510 (PDF 654.5 kb), and STNW3511 (PDF 2.1 mb).

We are continuing to work toward the implementation of the Dynamic Customer Standard. We see this as an essential solution for the future and stability of the network whilst enabling greater levels of Consumer Energy Resources (CER) to be adopted, including solar PV.

However, dynamic limits are designed to maximise the interaction of inverters with the electricity network and will be applied independent of the emergency backstop mechanism.

Importantly, an emergency backstop mechanism signal will have priority over any dynamic limits and will only be used in circumstances where all other mechanisms have failed to support the security of the electricity network.

We will undertake a review with AEMO, Powerlink and Department of Energy and Public Works within 12 months to review both the AEMO forecasts for minimum demand and the Emergency Backstop Mechanism.

Where an embedded network receives a connection approval under the relevant connection standard on or after 6 February 2023, which meets the backstop requirement (i.e. total amount of approved inverter capacity at the connection point of the embedded network to the distribution network is 10kVA and above), all new or replacement inverter energy systems must have a either GSD fitted to each inverter, or utilise the multi-inverter option of a single GSD connected to a Demand Response Controller.

Sites that use multiple inverters have the option of installing a GSD at each inverter or using a single GSD connected to a site controller (acting as a Demand Response Controller). Section 8.10.2 Emergency Backstop Mechanism of the Queensland Electricity Connection Manual (PDF 19.8 mb) provides guidance on the wiring requirements, including for multi-inverter sites.

If you have any further specific enquiries about your proposed site controller arrangement, please contact tech.enquiries@energex.com.au.

The option of a site controller has been provided based on feedback from RPEQ’s who design solar systems in Queensland. Please consult with an RPEQ if this option is of interest to you.

The signalling of the emergency backstop mechanism is through AEMO’s Minimum System Load market notices framework. This notice will issue market signals that ensure market price, VPP and aggregator activities support the increasing of minimum system load, or minimum demand on the network.

Through the consultation process, it was identified that some energy storage installations may be prevented from helping to address the minimum demand issue, and therefore dedicated energy storage systems were excluded from the emergency backstop mechanism requirements.

However, as the operation of IES that includes both rooftop solar PV and energy storage (otherwise known as hybrid inverters) will likely still be exporting into the electricity network, these have still been included in the emergency backstop mechanism and will require a GSD.

No. In the case where a hybrid inverter is installed with no solar PV attached directly to it, just an energy storage device, it does not require a GSD.

If the customer wishes to add PV to this inverter in the future, a connection application would need to be submitted and a GSD would need to be added at that time, assuming the system otherwise met the backstop mechanism requirements (i.e. total PV capacity of 10kVA in a non-AFLC area) as outlined in the relevant Connection Standard.

Please note: The calculation of the total capacity includes all inverters on the premises, including those solely supplied by a battery.

Sites that have a:

• hybrid inverter that is fed solely by solar PV; and
• separate inverter fed solely from a battery

would require a GSD to be installed on the solar fed inverter only (not on the battery fed inverter), where the requirements for backstop mechanism are met, noting that the calculation of the total inverter capacity threshold of greater than or equal to 10kVA, includes all inverters on the premises, including those solely supplied by a battery.

If the inverter is connected behind a ‘break-before-make’ switch, then it is considered off-grid and not considered under the total inverter capacity for the premises.

DRM 0 function when activated operates a disconnection device for the inverter. A hybrid inverter that does require a GSD will operate the disconnection device when DRM 0 is asserted. Whether the inverter capable of off-grid mode is capable of supplying off-grid loads when the disconnection device has operated, will be based on the manufacturer’s design.