For a larger embedded generator (e.g. over 200 kW), distribution networks can require direct and granular visibility and control of plant operation to ensure safety, reliability, and quality of supply. Unlike small-scale CER managed through inverter standards or CSIP-AUS, these connections are typically governed by site-specific agreements and required the implementation of a SCADA scheme. The objective is to provide DNSPs with the ability to remotely monitor performance, coordinate generator behaviour (including generation or export limits) and enforce disconnection when required within a network protection scheme.

These requirements will be defined and agreed as part of a negotiated connection between the DNSP and the customer, with the customer responsible for specific aspects of the solution’s operation. This ensures that the generator’s operation remains compliant with the technical limits and safety obligations of the network and provides DNSPs with enforceable mechanisms to manage network risks.

While technical obligations vary depending on the connection voltage, generator technology, and DNSP, there is some commonality in the types of requirements applied across DNSPs.

At a minimum, generators will generally need to implement utility-grade interconnection protection, anti-islanding controls, and SCADA telemetry to support DNSP operational needs. For larger systems and connections (e.g. above ~1.5MVA or connected to a HV network) additional functions such as remote trip, intertripping schemes, and detailed commissioning tests may be required. In addition, some jurisdictions require engineering sign off (e.g., via the National Engineering Register or state-based registers) as well as witness testing.

Integration methodologies 

The purpose of the SCADA integration is to establish a reliable interface between the DNSPs control systems (typically comprised of PLCs, RTUs and a SCADA Master Station) and the customer’s site controller or PLC. This allows the DNSP to remotely monitor plant status, issue trip or close-enable commands, and coordinate generator behaviour with network protection systems.

Two approaches are commonly used with each DNSP having different preferences based on the technology and connection type.

• SCADA protocol integration: This is the standard method used for telemetry and control of larger embedded generators. Through this interface, DNSPs continuously monitor relevant telemetry points. In return, they typically provide signals such as a “safe to connect” or “heartbeat” back to the embedded generator. These exchanges allow visibility of generator behaviour under all operating conditions. For example, AusNet specifies DNP3 telemetry for embedded generators of 1.5 MVA and above, while CitiPower/Powercor require a continuous SCADA-quality communications link for all HV network connections to its network.
• Discrete I/O signalling: This is typically used for critical control and protection functions, where rapid and fail-safe operation is required. Implementation is usually via hardwired (electrically isolated) Voltage-Free Contacts or trip relays that bypass protocol latency and ensure deterministic operation. SAPN illustrates a hybrid approach in which DNP3 with heartbeat is used for monitoring, but discrete trip signals are still employed as a backup in the event of communications failure. Similarly, CitiPower/Powercor allow for hardwired signals at the interface cubicle as an alternative to DNP3, particularly for intertripping and protection functions.

From a product design perspective, it is important that site controllers can accommodate a variety of communications methods, typically SCADA protocols over TCP/IP, one or more discrete I/O channels, and in some cases, 4–20 mA analogue signals. These requirements can materially change the design of the edge controller and often favour solutions built on an RTU or PLC hardware, rather than microcontroller platforms (e.g., Raspberry Pi) which are more commonly seen in micro EG solutions.

Important: Integration methods and signal lists vary between DNSPs. Product developers should always check the specific DNSP guidelines and the connection agreement for the site, as requirements are legally binding and customers are liable for breaches. In addition, integrations with mechanical or electrical interlocks as well as primary and secondary Protection Schemes may be required.