AS/NZS 4777.1, Grid Connection of Energy Systems via Inverters – Part 1: Installation Requirements was published in August 2024. The new version, AS/NZS 4777.1:2024, contains a series of changes to make electrical installations safer and Australia’s electricity supply more reliable. It also reflects new developments in inverter technology and the growing prevalence of solar PV systems, battery storage, and electric vehicles (EVs).

This standard is a crucial component of the safe and reliable connection of inverter energy systems to the national grid. With increased use of renewable energy technologies, uniform installation standards ensure grid stability while making cleaner, decentralised energy production possible.

When Does the New Standard Come Into Effect?

From 23 February 2025, all newly installed low-voltage connected inverters are required to meet AS/NZS 4777.1:2024. Concurrently, these systems need to satisfy the performance and functional requirements specified in AS/NZS 4777.2:2020. Notably, the contract or sale date is not deemed an acceptable exemption—installations performed from 23 February onward need to satisfy the revised standard irrespective of when the contract was entered into.

What about Distribution Network Needs?

Installers are also required to comply with the individual requirements established by the local distribution network service provider (DNSP). For those in the Energex and Ergon Energy networks of Queensland, it involves adhering to several network-specific standards. These consist of documents regulating low and high voltage small and large embedded generator connections, as well as dynamic connection requirements and guidelines included in the Queensland Electricity Connection Manual.

High Voltage Connections and Existing Contracts

It has been queried as to whether the existing contract, entered into prior to 23 February 2025, enables installation to proceed under the 2016 standard. No is the reply. If at low voltage, connection by inverter, installation from that date onwards must adhere to AS/NZS 4777.1:2024. Even if the total DNSP connection is high voltage, but the inverters themselves are low-voltage connected, the new standard still applies. Only those inverters that directly connect at high voltage, or rotating machines, are exempt from AS/NZS 4777.1:2024 and are required to meet the high-voltage standard STNW1175.

Required Design and Compliance Reports

For systems larger than 30 kVA within Energex and Ergon Energy’s territory, a Design Certification Report (DCR) or Compliance Report (CR) has to be provided. These reports verify that the installation and design of the system comply with all relevant standards. These documents have templates available on the respective networks’ websites.

RPEQ Certification Still Required

No updates have been made to the current requirement for certification as Registered Professional Engineer of Queensland (RPEQ). All embedded generating systems covered by STNW1174, STNW3511, or STNW1175 must be designed and commissioned by a RPEQ under supervision so that they conform to all technical and safety requirements.

New Terminology: Interface Protection

One of the key terminology adjustments in the 2024 standard is substituting “central protection” with “interface protection.” This terminology is now used for protection equipment located downstream of the site main switch but upstream of the inverters. The revision adds clarity to system architecture and simplifies separating different layers of protection.

Interface Protection for Larger Systems

Under AS/NZS 4777.1:2024, interface protection is mandatory for inverter energy systems, or aggregated systems, with a capacity of more than 200 kVA. Some exceptions, however, exist, particularly in systems that incorporate inverter power sharing devices or are embedded networks. These instances are covered extensively in supporting supplementary FAQs to the standard.

Interface Protection Settings for Queensland

For applications in the Energex and Ergon Energy grids, interface protection settings should conform to the Region Australia A profile of AS/NZS 4777.1:2024. As an illustration, over-voltage protection should activate at 267 volts with a trip delay of 2.5 seconds and a maximum disconnection time of 3 seconds. Under-voltage protection is necessitated at 179 volts (with a 11.5 second delay) and 69 volts (with a 2.5 second delay), with a 3-second disconnection limit for each. Over-frequency and under-frequency limits are 52 Hz and 47 Hz respectively. Acceptable rate of change of frequency is ±4 Hz per second, with 0.5 seconds trip delay and 1 second maximum disconnection time.

Inverter Capacity and Export Limits

The regulation places definite limitations on inverter capacity and exporting levels for single-phase connections. For static connection, single-phase inverters can only be used up to 10 kVA, with exporting limited to 5 kW. On SWER lines, it is limited down to 2 kW. For dynamic links, the maximum inverter capacity can comprise 10 kVA for PV and a further 10 kVA for energy storage, as long as export levels are kept within 1.5 to 10 kW depending on the configuration of the network. It is worth mentioning that for hybrid or multimode setups, the overall capacity of the inverter is still under port limitations, not merely the total output.

Phase Balance for Multi-Phase Installations

Phase balance is of paramount importance in multi-phase systems. The 2024 standard covers elaborate requirements to balance the power flow. Single-phase inverters for energy storage or PV systems shall not be over 5 kVA for any single phase when in systems that do not exceed 50 kVA. Both the battery system and the PV system must, when both are installed, be wired on the same phase. A phase imbalance of greater than 5 kVA overall is not allowed, though phase balance protective devices are not needed at this size.

Vehicle-to-grid (V2G) or vehicle-to-building (V2B) inverters are granted some tolerance.

A single-phase inverter that is employed for such purposes can be rated at a nameplate of as much as 8 kVA if it is equipped with generation limit control to a maximum of 5 kW. Generation limit control is not an approved technique for attaining phase balance except in these special V2G or V2B applications. It does not modify the inverter’s nameplate rating or apparent power classification.