I. Overview SCADA (Supervisory Control and Data Acquisition) systems are computer-based automation systems for production process control and dispatching. They monitor and control on-site operating equipment to achieve functions such as data acquisition, equipment control, measurement, parameter adjustment, and various signal alarms. Currently, SCADA systems are widely used in data acquisition and monitoring control, process control, and many other fields, including power systems, water supply systems, petroleum, and chemical industries. Because the requirements for SCADA vary across different application areas, the development of SCADA systems in different application areas is not entirely the same. In power systems, SCADA systems are the most widely used and technologically mature. As a major subsystem of the Energy Management System (EMS), it has advantages such as complete information, improved efficiency, accurate understanding of system operating status, accelerated decision-making, and the ability to quickly diagnose system fault conditions. It has become an indispensable tool for power dispatching. It plays an irreplaceable role in improving the reliability, safety, and economic efficiency of power grid operation, reducing the burden on dispatchers, realizing the automation and modernization of power dispatching, and improving the efficiency and level of dispatching. However, despite the increasing maturity of the SCADA industry in power system applications, a wide variety of monitoring and configuration software with different features, such as iFix from GeFUNC, WinCC from Simens, Intouch from Wonderware, Citect SCADA from Citect, KingSCADA from Asia Control, Zijingqiao monitoring and configuration software from Zijingqiao, and ControX from Turing Kaiwu, occupy the market. However, most SCADA software uses general templates. Although it has a wide range of applications, very few are specifically designed for the characteristics of power systems. Moreover, most of the SCADA software for power systems is designed for power plants and substations, and none are specifically designed for low-voltage electrical appliance testing. Compared to ordinary power plants, low-voltage electrical appliance testing stations require significantly more frequent equipment operation and a corresponding increase in the number of times operators need to enter and exit the operating area. This places higher demands on equipment reliability and system safety. Furthermore, some low-voltage electrical appliance tests require precise control of test time and data acquisition, functions that traditional SCADA software and PLC systems cannot perform. Therefore, the integration of timing controllers, data acquisition devices, and other components is necessary. We utilize Citect's CitectSCADA software and Schneider Electric's Modicon Premium series PLC as the core to build a control platform. This platform is further enhanced by a hardware and software safety interlock system, a timing generator, a time-current protection unit, and data acquisition devices, forming a complete testing platform. In the design, in addition to considering the characteristics of ordinary power systems, we also fully considered the characteristics of low-voltage electrical appliance testing stations and the platform's versatility and scalability. Currently, this design has been applied and is operating well on the Schneider Electric low-voltage electrical appliance testing station short-circuit test platform. II. Structure of the Low-Voltage Electrical Appliance Testing Monitoring System The low-voltage electrical appliance testing monitoring system consists of five parts: a monitoring computer and monitoring software, a programmable logic controller (PLC), a programmable sequence controller, a safety interlock system, and a data acquisition system. Specifically: the industrial control computer and monitoring software control and monitor the equipment and testing process; the PLC implements static control and safety interlocks for the test circuit; the sequence controller implements precise sequential control of the testing process; the safety interlock system ensures the test is conducted under safe conditions through hardware and software interlocks; the data acquisition system consists of a data acquisition display and a data acquisition cabinet, mainly including a data isolation amplifier, a data acquisition system, and a computer, to acquire current and voltage data during the test. The monitoring software is developed using CitectSCADA, featuring an open human-machine interface, supporting multiple standard communication methods and network communication protocols, and allowing easy integration of various control devices and instruments into the system. The web gateway function allows users to access data from anywhere via the internet. The system has good reliability. Users can select the test mode, test type, and switch action sequence using a mouse. The test parameters, equipment control, and status display of the programmable controller system are set via Ethernet. The main functions of the monitoring software are: (1) Test circuit preparation and input of test parameters, including test sample type, test parameters, test type, test sample location, test circuit, action switch, energizing time, test cycle number, etc. (2) Automatic or manual control of various electric switches under necessary safety interlock conditions. (3) Display of single-line simulation circuit diagram of the main test circuit, dynamically simulating the status of the switching equipment and the test process through different colors and shapes. Including equipment status, test status, abnormal status, etc. (4) Display of the energized status of the main circuit equipment. (5) Control of test start and stop and record test duration. (6) Display of safety interlock and necessary test conditions. (7) Check of safety interlock and necessary test conditions. Under automatic operation, in order to start the test normally, the relevant status needs to be checked. The test can only be started if the relevant status is normal. All of these information are realized by passive contacts. If any status is abnormal, the program controller will terminate the operation and display a prompt message. The programmable logic controller (PLC) is implemented using a Modicon TSX Premium series PLC, exchanging information with the monitoring computer via Ethernet through the XIP protocol based on TCP/IP. The system includes a set of manual selection switches and control switches for testing equipment; these switch signals are all input to the PLC's digital input. The PLC is responsible for collecting signals indicating the status of medium-voltage circuit breakers, low-voltage circuit breakers, closing switches, grounding switches, test specimens, doors in each test chamber, system alarm signals, and the readiness status of each device. In manual mode, it can also control individual circuit breakers and other equipment to meet commissioning needs. When time accuracy requirements are not high (above 50ms), the PLC can control the test sequence. However, in short-circuit systems where high time accuracy is required, a programmable timing controller (PTC) is used to control the test sequence. The PTC is used to control equipment related to the test sequence, with an accuracy higher than +/-2ms. The system utilizes products from Nicolet, Inc. (USA). The entire hardware is centrally located within the control cabinet. Information exchange with the programmable logic controller (PLC) is via passive contacts. Channel parameters, including channel output start time and duration, can be set and displayed through a human-machine interface (HMI). The safety interlock system consists of both hardware and software components. The software is contained within the monitoring software, which automatically determines whether the test conditions are met based on information obtained from the PLC. The hardware comprises four parts: series dry contacts, safety door locks, safety modules, and a time-current protection unit. Series dry contacts connect the auxiliary contacts of the equipment requiring interlocking to the operating circuit of the equipment restricted by the interlocking conditions, thus achieving hardware interlocking between devices. The safety door lock uses an imported French safety lock system. The key can only be retrieved from the key box on the control panel to open the door when safety conditions are met; if the door is open, the test cannot proceed, further ensuring the personal safety of test personnel. The safety module uses a Modicon safety module, providing an additional layer of hardware protection independent of the above components. The time-current unit is used to promptly disconnect the system when problems are detected during the test, ensuring equipment safety. It also employs a separate hardware unit to ensure safety. The data acquisition system includes current and voltage sensors, signal isolation channels, the data acquisition system itself, data acquisition software, computer hardware, and computer report processing and printing software. III. System Features and Suggestions for Further Development In the design, we considered the platform's versatility and portability. Therefore, from the outset, we designed a component library containing major equipment such as circuit breakers, transformers, and closing switches, including equipment parameters, fault signals, location, and status information. Although this part of the work is too complex for a single project, as the component library is gradually enriched, the subsequent design work will gradually simplify into a "building block" process, which is precisely the effect desired in building a universal platform for low-voltage electrical appliance testing systems. The modular encapsulation of the PLC program design is also considered in light of the needs of building a universal platform for low-voltage electrical appliance testing systems. We are attempting to gradually encapsulate commonly used test sequence programs for low-voltage electrical appliances into independent standard modules, and on this basis, gradually build a complete test sequence program library. In subsequent work, users only need to select the corresponding program and input the interface parameters for convenient use. The openness of the monitoring software is also a feature of this system. We provide a user-friendly interface for secondary development, such as modifying system parameters and test circuits. Users can make partial adjustments to the program according to their testing needs without affecting the software system's security. This open interface for secondary development can serve as a starting point for building a general platform interface model, providing some reference information for the interface design of a general platform for low-voltage electrical appliance testing. As mentioned earlier, the four-fold hardware and software interlocking, combined with comprehensive safety design, is also a characteristic of this system. Adhering to the principle of human-centeredness, the importance of safety cannot be ignored for either personnel or equipment. Therefore, while meeting functional requirements, the system design particularly emphasizes the principle of safety first. Given the frequent operation of low-voltage electrical appliance testing stations, multiple safety considerations ensure preparedness. The successful application of the short-circuit test platform in the low-voltage electrical appliance testing station project has provided a good start for the construction of a general-purpose testing platform for low-voltage electrical appliances. In further work, this platform needs continuous improvement and enrichment in the following aspects: The database needs further expansion. Different projects have different characteristics, and it is clearly impossible to expect a database built for one project to meet the needs of all projects. Therefore, both the component library and the test program database need continuous improvement and enrichment in future projects to ultimately achieve practical results. Migrating the current database to a more universal database is also an urgent problem to be solved. Currently, the component library can only be used with CitectSCADA monitoring software, and the PLC program module can only be further edited and developed using UnityPro programming software. It is clearly unlikely that both software programs will be used in future projects. Therefore, in the next step, it is necessary to migrate the various components in the component library to ActiveX modules, which are applicable to any monitoring software development platform. The PLC program module also needs to be further migrated to a standard module that conforms to IEC61131 and is applicable to various PLC systems. IV. Conclusion This paper, through the design of the short-circuit platform for the Schneider Electric low-voltage electrical appliance testing station project, has initially established a general-purpose monitoring and configuration software platform for low-voltage electrical appliance testing stations. It also lays a solid foundation for the future improvement and expansion of this platform, providing reference material for filling the gap in monitoring and configuration software applications in low-voltage electrical appliance testing station projects. Author's Affiliation: Engineering Department, China Machinery International (Xi'an) Technology Development Co., Ltd. Address: Engineering Department, China Machinery International (Xi'an) Technology Development Co., Ltd., No. 128, East Section of Huancheng South Road, Xi'an, 710054, China Email: [email protected]