Currently, substation integrated automation has developed rapidly, especially with the implementation of the power system's "standardization and first-class" initiative. Many substations nationwide have achieved integrated automation, and some 220 kV and 110 kV substations are now capable of unmanned operation. The following section introduces the specific content of a substation integrated automation system; analyzes the problems existing in the construction of integrated automated substations; and discusses its future development. [b]1 Basic Contents of a Substation Integrated Automation System[/b] The basic contents of a substation integrated automation system include five parts: relay protection, fault recording, "five-proof" interlocking, measurement and control system, and communication system. Relay protection includes line protection, transformer protection, capacitor protection, etc. The line protection section includes starting elements, zero-sequence current elements, zero-sequence direction elements, distance elements, oscillation blocking elements, TV disconnection alarm, CT disconnection alarm, control circuit disconnection alarm, and automatic reclosing. Transformer protection consists of differential protection, composite voltage blocking overcurrent protection, zero-sequence overcurrent protection, zero-sequence overvoltage protection, overload protection, and TV disconnection protection. Capacitor protection consists of overcurrent protection, unbalanced current protection, overvoltage protection, undervoltage protection, and unbalanced voltage protection. Fault recording primarily records the dynamic changes in voltage and current before and after a fault, as well as the status of switching quantities. The management computer system includes an expert system that provides standard operating tickets and allows for hard-locked operations via computer. The expert system also facilitates convenient and intuitive anti-accident drills without affecting the normal operation of other functions. In addition to local measurement and control, integrated automated substations also have relatively complete remote control systems. The "four remote" requirements of remote control systems are specifically reflected in integrated automated substations, especially in unattended substations. The main contents of the measurement and control system are switch control, transformer voltage regulation, compensation capacitor voltage regulation, low-frequency load shedding, and substation parameter acquisition. Through communication networking, the substation achieves information transmission with the dispatch system, thus completing the "four remote" functions. [b]2 Substation Relay Protection and Integrated Automation[/b] The installation location of substation relay protection has changed significantly compared to the past, basically considering two methods: ① local installation; ② centralized installation. Some substations only consider one method, while others use both. In a typical design, 10 kV line protection is installed on the switchgear, while transformer and high-voltage line protection are centralized in the control room. The relay protection device is networked with the management computer via communication lines. This consideration is mainly because 10 kV switchgear is generally installed indoors, while transformers and high-voltage line switches are installed outdoors. The development of microcomputer technology, i.e., the application of single-chip microcomputer technology, has made it possible for protection to be independent of the management computer and to establish communication with it. Thus, relay protection has not become an internal part centered on a large computer. As part of an integrated automation system, relay protection is structurally and functionally independent, but its management is based on mutual communication, a model widely accepted. Relay protection is not only part of the integrated automation system but also independent of it; this design is undoubtedly essential for the reliability of the entire system. [b]3 New Achievements in Integrated Automation Substations[/b] Several new technologies, processes, equipment, and research results have been successively applied to the integrated automation system of substations. 3.1 Low-Current Ground Fault Selection With the successive deployment of microcomputer-based low-current ground fault selection devices, these products have undergone rigorous hardware screening, implemented a series of anti-interference measures in their structure, and incorporated self-testing programs and detection mechanisms to prevent malfunctions in their software. This has enabled low-current ground fault selection protection to achieve near-perfect operation. 3.2 Mechanism-Based Protection Mechanism-based protection is a type of protection that prevents relay contacts from burning out when a switch fails to operate. Statistics show that in low-voltage systems, the burning out of trip relay contacts is common due to quality issues with the switching mechanism. The introduction of mechanism-based protection has completely solved the problem of relay burnout. 3.3 DC Grounding Selection Device Due to the complex wiring of the DC system in substations, grounding phenomena frequently occur during operation. In recent years, relatively successful DC grounding selection devices have been put into operation, basically realizing the goal of selecting grounding points without pulling the circuit, and improving the reliability of substation operation. 3.4 Clock Calibration System Substation microprocessor-based protection and automatic devices are equipped with event recording functions, using internal clocks to record parameters related to faults and other events for sequential recall. The recorded time is divided into year, month, day, hour, minute, second, millisecond, and microsecond. This setup is impeccable for a single device. However, for substations and dispatch management systems, due to the existence of internal clock errors, the deviation inevitably becomes too large over time. After adopting clock calibration measures, the event times will be completely unified. [b]4 Characteristics of Operation and Management of Integrated Automated Substations[/b] The management of integrated automated substations has many characteristics compared to conventional substation management, analyzed as follows. 4.1 Network Management System A simplified diagram of the substation's network management system is shown in Figure 1. The substation utilizes management units to transmit data, manage and monitor relevant units within the substation, perform related operations and queries, automatically alarm when an abnormality occurs in a relevant unit, and record and print waveforms before and after a fault occurs in protected equipment. The management unit largely replaces manual inspections during operation, offering greater timeliness, speed, and accuracy. However, it cannot replace manual inspections in certain special circumstances, and handling abnormalities in relevant units still requires human intervention. 4.2 Networking with the Dispatch Automation System Common substation networking methods with dispatch automation systems are shown in Figure 2. Networking with the dispatch automation system provides conditions for remote measurement, remote adjustment, remote signaling, and remote control, enabling unmanned operation. The dispatching department can monitor or operate each substation through the dispatch automation system. 4.3 Operational Characteristics Integrated automated substations can operate circuit breakers and disconnectors manually or automatically. For unattended substations, switching operations are primarily remote, depending on the equipment configuration. For example, if load switches can be operated remotely, local operation is generally unnecessary. However, operations such as grounding switches must be performed locally. Integrated automation cannot handle operations that can only be performed locally; typical configurations still require on-site personnel. Furthermore, post-power outage procedures such as voltage testing and grounding wire installation cannot be performed by integrated automation. In such cases, for manned substations, the on-duty personnel will handle the procedures; for unattended substations, an operations team must be dispatched. 4.4 Characteristics of Equipment Abnormalities and Accidents Compared to ordinary substations, integrated automated substations, due to the large size and complexity of their automation and remote control systems, experience significantly more problems due to equipment abnormalities and accidents. According to some power supply bureaus, these accidents account for over 30% of all incidents. Therefore, under the same conditions, integrated automated substations encounter more problems than ordinary substations. Accident handling at unmanned substations is obviously more complicated than that at manned substations.　[b]5 Trends in the Development of Substation Integrated Automation[/b] 5.1 Advantages of Substation Integrated automation Substations have many advantages. Their emergence has strengthened information transmission and facilitated many aspects of work. For example, the MPS-4000 substation integrated automation system has the following advantages: (1) It simplifies the hardware configuration of secondary equipment. Since the data collected by the secondary equipment can be shared by various parts through the communication bus, the sampling part and the data processing part only need to collect data once for each parameter to meet the data requirements of different functions. Integrated automation substations can eliminate the need for dedicated fault recorders, dedicated control signal panels and dedicated central signal panels. (2) It simplifies the wiring of secondary equipment. All the secondary functions of the substation's lines, transformers, capacitors and other primary equipment are concentrated in one or several boxes. The connection between different secondary equipment can be realized by the bus, thus eliminating the need for cable connections between secondary equipment. (3) It simplifies the debugging of equipment. Due to the modularization of hardware and the digitization of sampling values, the factory debugging and operation and maintenance debugging are much simpler. (4) It facilitates the handling of primary accidents. The equipment's self-test function enables it to alarm in time when the equipment itself malfunctions; the equipment's fault recording function enables it to record the parameters and events at the time of the fault when the system malfunctions, so as to facilitate analysis and processing. 5.2 Problems still existing in substation integrated automation (1) It is difficult to unify the design specifications. Although the State Power Corporation and the power departments of various provinces have made unified regulations on the design of substation integrated automation systems and the performance indicators of equipment, the component selection, hardware configuration, circuit structure, manufacturing process and software program of equipment manufacturers are very different. These differences lead to significant differences in equipment lifespan, performance, anti-interference ability and management and maintenance. (2) The one-time investment of equipment is too high. Although integrated automation substations save wiring, facilitate installation and construction, and simplify debugging, the cost of modern equipment products such as relay protection, communication system, centralized control, and remote control system is relatively high. Therefore, the one-time investment of integrated automation substation equipment is higher than that of conventional substations. For example, the investment in the automation equipment of a 110 kV integrated automation substation with the same substation capacity is more than twice that of conventional substation equipment; usually, the automation part of a typical 220 kV substation costs more than 1.5 million yuan. (3) The equipment still requires regular maintenance. To date, almost no integrated automation system for substations is maintenance-free. On-site handling of equipment abnormalities is limited to replacing plugs or components as needed. Further analysis and in-depth inspection and handling often require the manufacturer's assistance. (4) The problem of malfunctions still exists. A 35 kV line in a 110 kV substation malfunctioned and tripped 24 times in one day. The final investigation revealed that the temperature characteristics of the protection element had deteriorated, and the current sampling value drifted upward during operation until it reached the overcurrent protection setting value, at which point the overcurrent protection tripped. Although this phenomenon is not common, such reliability is still worrying. (5) The operation of the equipment and the handling of accidents are relatively complicated. In some areas, the general operation of unmanned substations is still carried out on-site by the "operation team" to avoid the inability to handle abnormalities in remote operation in a timely manner. In addition, once the substation integrated automation equipment malfunctions, even a minor fault, personnel must be dispatched to the site. (6) Limited equipment lifespan. The lifespan of substation integrated automation equipment is generally only about 15 years. After the service life expires, new products must be replaced. (7) Insufficient monitoring of remote control equipment. At present, substation integrated automation has mainly improved in terms of processing speed, capacity, accuracy, and event recording resolution. However, the self-testing of remote control terminals and substation integrated automation itself, as well as the monitoring of the operating status of input and output boards, have not been developed. For example, the detection of UPS power supply and the detection of remote control terminal self-test information are not perfect. The improvement of these functions still requires a process of understanding and practice, involving manufacturers to improve equipment, add self-test information of remote control equipment, and revise the power system remote control protocol. 5.3 Factors that have enabled the development of substation integrated automation In the past decade or so, the automation level of the power system has developed rapidly, with numerous automation systems emerging, including dispatch automation, substation automation, distribution automation, urban grid automation, and rural grid automation. The development of substation integrated automation also has its historical reasons, which are analyzed as follows: (1) The need for power grid development. Substation integrated automation has certain advantages. In order to improve the overall automation level of the power grid and to match the dispatch automation of the power grid, a certain scale of substation integrated automation system should be developed. (2) The need to create first-class work. The State Power Corporation has clearly stipulated the proportion of integrated automation substations in its first-class enterprise standards. Therefore, those enterprises striving to create first-class enterprises must complete the indicators of integrated automation substations as stipulated. (3) The need to reduce manpower and increase efficiency. According to statistics, in some regions, the number of substations has doubled and the substation capacity has doubled in less than 10 years. However, the number of production management personnel has not increased but has decreased. Under such circumstances, in order to complete the annual production tasks and maintenance tasks, it is necessary to vigorously develop highly automated systems to reduce the workload of equipment maintenance and debugging, and at the same time reduce the burden on staff. It can be seen that the development of substation integrated automation has both subjective desires and objective needs. It is worth noting that the production department should strengthen the front-line force, reduce the labor intensity of production personnel, improve work efficiency, and ensure work quality. 5.4 The development scale of substation integrated automation must be controlled. The number of highly integrated automated substations and unmanned substations must be controlled within a certain proportion, so as to meet the needs of the main grid integrated automation, take into account China's national conditions, the overall economic strength of the country, and the population factors of the country. China's population problem is extremely prominent. As a major pillar of the national economy, the power sector cannot avoid it. Each sector should absorb personnel in an appropriate amount to alleviate the employment pressure of society. On the one hand, the construction investment cost of integrated automated substations is too high, and the average life of automated equipment is too short. On the other hand, the problem of highly developed automated equipment competing with people for jobs has occurred in the development process of developed countries. As a department of macro-control, it should guard the first gate to avoid repeating the same mistakes. The development of substation integrated automation should be considered in a coordinated manner and treated differently. The following problems should be solved macroscopically. (1) Remote areas. For substations where the survival and living conditions of on-duty personnel are difficult, the issue of substation integrated automation can be considered. If conditions permit, it can be done to the point of being unmanned. (2) Hub substations. For hub substations, a more advanced integrated automation configuration should be considered. However, hub substations should be managed by on-duty personnel. Unmanned operation is not advisable. (3) General substations. For general substations, protection, automation, remote control, communication, etc. should be appropriately considered according to the design principles and actual conditions, that is, to reach the so-called semi-automation level or below. As long as the above problems are solved well on a macro level, the development of substation integrated automation system will be satisfactory. This way, we can see the symbol of modern level and take into account the overall situation and the supporting development with other industries. 6 References 1 Zhao Qinzeng. Suggestions on increasing remote control and related equipment information. Power Grid Technology, 2001 (3)