With the deep integration of IoT technology, artificial intelligence technology, 5G, and grid operations, traditional distribution terminal equipment (FTU, DTU, TTU) in the power distribution field can no longer meet the smart grid requirements of the Distribution IoT. These terminals are rapidly transforming into intelligent devices featuring deep integration of primary and secondary systems. Conventional testing methods struggle to comprehensively validate the closed-loop interaction functions between distribution automation terminals and the power grid. To address this, KeLiang has developed an HIL-based simulation test system for distribution automation terminals. This system constructs a simulation model of the actual distribution network in real-time simulation software, compiles and downloads it to a real-time simulator for electromagnetic transient simulation of the distribution network. The real-time simulation results are output via signal interfaces and connected to the terminal under test, forming a flexible hardware-in-the-loop test circuit. This approach more closely replicates actual field testing conditions, enabling more accurate closed-loop testing of the primary-secondary fusion functions of distribution automation terminals.

The closed-loop simulation testing system for the KeLiang distribution automation terminal mainly consists of a test server (including a network switch, a workstation, and test software located in the workstation), a real-time simulator (including a typical network topology model for real-time simulation, a simulator processor, and IO interfaces), signal interfaces (including analog quantity interfaces and digital quantity interfaces), and the distribution automation terminal equipment under test.

The real-time simulator can perform electromagnetic transient real-time simulation on the distribution network system, such as real-time simulation analysis of power sources, bus bars, transformers, circuit breakers, and loads; the simulator and the test server are connected via network cables. The configuration of the simulator’s I/O boards can be determined based on the scale of the distribution network model simulation and the requirements of the device under test (distribution automation terminal equipment). Generally, through analog interfaces (e.g., digital simulation power amplifiers), the simulator’s output analog small signals undergo power amplification and are then connected to the analog contact points of the tested distribution automation terminal. Through digital interfaces (e.g., simulated circuit breakers), the simulator’s digital signals are converted into switching signals compatible with the tested terminal and then connected to the switching contact points of the tested terminal. This achieves closed-loop simulation testing of the tested distribution automation terminal, providing a complete set of simulation test solutions for research and engineering verification of the primary-secondary fusion functions of distribution automation terminals, and offering a new test technology support that is closer to field application scenarios for the large-scale, safe, and reliable grid integration of distribution automation terminals.

Referring to published standards (as shown in Table 3-1) and Document No. Distribution IoT 5: "Notice on Issuing Technical Specifications for Station Area Intelligent Integrated Terminals", the primary test functions supported by KeLiang’s Closed-Loop Simulation Test System for Distribution Automation Terminals are detailed in Table 3-2.

Case No.1

Closed-loop Simulation & Testing Case for Smart Distributed Function of a Customer’s Distribution Automation Station Terminal

Project Overview: Smart distributed terminals enable rapid fault location, isolation, and power supply restoration. Consequently, feeder automation (FA) technology based on smart distributed systems is increasingly deployed in critical urban distribution networks. However, interoperability between multi-vendor terminals demands extremely high consistency in communication models and functional logic, resulting in low success rates in actual engineering projects. To address this, a Hardware-in-the-Loop (HIL) simulation & testing system and methodology has been developed for interoperability testing of smart distributed automation DTUs.

This project employed a typical distribution network test model for smart distributed DTUs. Real-time simulation results aligned with actual field conditions, with dynamic responses accurately replicating on-site operational scenarios, providing an effective solution for distributed DTU testing.

Project Outcomes: 

• Established a complete distribution automation test environment to validate the smart distributed functions of DTUs;

• Reduced client testing costs by 30–45% and improved testing efficiency by 50% (estimated from industry cases;

• Verified compliance with national standards and technical requirements for grid integration of distribution automation terminals.

    Case No.2

Closed-loop Simulation & Testing Case for Local Feeder Automation Function of a Customer's Distribution Automation Feeder Terminal

Project Overview:

The Feeder Terminal Unit (FTU) primarily monitors pole-mounted medium-voltage switches, performing functions such as telemetry, teleindication, and telecontrol. It enables fault location, isolation, and rapid power restoration in non-fault areas, playing a critical role in stabilizing distribution networks.

To address challenges in coordinated group testing for massive distribution automation terminals and self-healing feeders, and to enhance the testing efficiency of self-healing circuits, a closed-loop simulation test solution has been developed. This solution integrates "typical distribution power flow simulation + Hardware-in-the-Loop (HIL) integration with multiple distribution automation terminals".

Project Test Results:

The test outcomes align with field conditions, with dynamic responses (e.g., voltage/current transients, protection actions) accurately simulating actual operating scenarios. This delivers an effective solution for testing multiple Distribution Automation Terminals (FTUs).

Key Achievements:

Comprehensive validation of local feeder automation functions (e.g., fault isolation, power restoration) for multiple FTUs was achieved, enhancing testing efficiency by 60–80% and enabling significant cost reductions for clients by replacing field trials with closed-loop HIL simulations.