For EG with a capacity of 200 kVA or greater, United Energy requires a Generator Monitoring Meter (GMM) to be installed. The GMM is an important component in the safety, compliance, and ongoing monitoring of the embedded generation system. The GMM is required to perform two key functions. First, it provides remote monitoring, allowing United Energy to continuously track the performance and status of the embedded generation system. This data helps the utility company monitor operational parameters such as power generation, system health, and grid conditions. It also enables early detection of potential faults or inefficiencies in the system, providing real-time insights into system operations.

The second function of the GMM is remote disconnection, which is an important feature for maintaining grid stability. If necessary, the GMM allows the system to be remotely disconnected from the grid. This capability ensures that the embedded generation system can be safely isolated in situations where the Australian Energy Market Operator (AEMO) requires disconnection to protect the grid. The remote disconnection feature eliminates the need for physical intervention, thus reducing the risk of network disruption during fault conditions. Section 11 of the UE-ST-2008.2 standard provides detailed specifications for the GMM, including installation guidelines, communication protocols, and data reporting requirements, ensuring uniformity and clarity in installation and operational procedures.

Compliance with Australian Standards

To ensure that embedded generation systems are safe, reliable, and operable, United Energy’s network access standard has several key Australian Standards to adhere to. Such standards will ensure a good integration of distributed energy systems into the national grid and uniformity across the industry without compromising safety.

The main one is AS/NZS 4777.2:2020, which prescribes performance and installation requirements for grid-connected inverters. It ensures that inverters operate safely and efficiently within specified voltage and frequency ranges. This standard covers essential features such as grid voltage and frequency tolerance, where inverters must be capable of automatically disconnecting if the grid voltage or frequency falls outside specified limits. This functionality prevents potential damage to both the inverter and the network. Inverters are also required to have anti-islanding protection to prevent the system from continuing to generate power when the grid goes down, to avoid any risk to the system and utility personnel.

For the systems with the Battery Energy Storage Systems (BESS), compliance with AS/NZS 5139:2019 will be necessary. This standard specifies the safe installation, maintenance, and operation of BESS units, focusing particularly on issues involving battery safety. The standard sets guidelines for fire prevention, chemical safety, and proper handling of battery systems so that damage or accidents are less likely to happen during operation. It also encompasses the power conversion equipment that interfaces with the grid, ensuring efficient and safe energy storage and discharge processes.

Both of these standards are imperative to ensure that the embedded generation systems meet national safety guidelines and are fit to be integrated into the broader electrical grid.

Protection and Control Settings

United Energy’s standard provides for specific protection settings for ensuring the stability and protection of the network. This is done with the intention of safeguarding the system and network from faults, voltage fluctuations, and abnormal conditions in the grid.

The inverters need to be programmed such that, under abnormal conditions of voltage and frequency, the system needs to automatically discontinue connection to the grid. In table 6, detailed configurations of overvoltage, undervoltage, overfrequency, and undervoltage trip can be obtained in the standard. In overvoltage protection, it must discontinue connecting if the voltage surpasses the established limit value usually about 253V in the grid. Similarly, for undervoltage protection, inverters should be disconnected at about 180V when the grid voltage drops below a certain level. As far as frequency protection is concerned, inverters should also be disconnected whenever the grid frequency exceed the predefined limits, either when grid frequency exceeds 51.5 Hz or moves below 47 Hz.

For systems using protection relays, their settings must be according to the standards specified in Table 8. These relays are designed to protect faults by isolating the embedded generation system from the network under fault conditions. Thus, faults, such as short circuits or overcurrent situations, do not propagate through the system and cause damage to both the embedded system and the broader grid. The protection relays must be set with proper time delays so as not to get tripped unnecessarily by minor disturbances, but then still provide proper disconnection at the onset of more serious disturbances.

Technical Studies and Commissioning

Proponents should conduct several technical studies before actually commissioning the LV EG system. These are load flow studies, which aim to assess whether the embedded generation system will actually affect the flow of power inside the network, and thus look for potential imbalances in either voltage or currents that might emerge from the implementation of the system. This serves to ensure the system does not destabilize the grid and guarantees its proper function.

Fault level assessments are also needed to determine the contribution of the embedded generation system to fault currents, ensuring that the protection equipment is appropriately rated to handle such faults without failure. Protection coordination studies are also necessary to ensure that the protection settings of the embedded generation system are coordinated with those of the network. This coordination prevents miscoordination that could lead to unnecessary disconnections or inadequate protection during fault conditions.

Once these studies are finalized and the system is found to satisfy all the requirements, United Energy will issue a Sanction to Connect, and it will be permitted to operate in parallel with the network.

Cybersecurity Considerations

As the energy grid becomes increasingly digitized, a part of its integration process necessarily involves cybersecurity. United Energy has a standard stipulating that the settings of any devices and equipment related to its embedded generation systems must be locked against unauthorized access or tampering. This implies that all important systems should be password protected with only authorized individuals having the resources and guides necessary to change settings.

These cyber security measures protect the integrity of the system and assure that the monitoring and controlling features, including remote disconnection are not affected.