**0 Introduction** Due to the important position and characteristics of 500 kV substations in the power grid, the adoption of integrated automation systems has high technical requirements. The Shuanglong 500 kV substation is the first substation in my country to completely eliminate conventional control and adopt full computer operation. Its integrated automation system was put into operation simultaneously with the substation in December 1997. More than a year of operation has shown that the system is safe, stable, and reliable, and all functions have met the design specifications and operational requirements. This article introduces the current status and operation of the Shuanglong substation's integrated automation system and analyzes the functions, technical characteristics, and advantages that an integrated automation system for ultra-high voltage substations should possess. **1 Functions and Technical Characteristics** The 500 kV Shuanglong substation's integrated automation system was procured through international bidding. Siemens won the bid and provided substation-level and lower-level equipment; the substation monitoring system was subcontracted by Siemens to the Electric Power Automation Research Institute, which was responsible for the integration of the entire system. Considering the integrity of the system and the ease of expansion, the station monitoring system of the integrated automation system is built in one go according to the long-term plan, while the station-level and lower equipment are built according to the medium-term scale of the substation. The schematic block diagram of its system structure is shown in Figure 1. [img=397,265]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dlxtzdh/dlxt2000/0006/image06/t5701.gif[/img][img=291,265]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dlxtzdh/dlxt2000/0006/image06/t5702.gif[/img] Fig.1 Structure of integrated automation system at 500 kV Shuanglong ultra-high-voltage substation The integrated automation system consists of a BSJ-200 substation monitoring system provided by the Electric Power Automation Research Institute and five Siemens LSA 678 devices located in each relay protection compartment. The hardware equipment of the station's monitoring system mainly includes dual host computers, dual human-machine interface workstations, main and backup communication units, and dual fiber optic Ethernet network equipment. The 500 kV Shuanglong substation integrated automation system collects 2,467 remote signaling points, 413 telemetry points, 104 pulse quantity points, and 424 remote control output points, achieving relatively comprehensive monitoring of the substation. Compared with conventional monitoring systems in ultra-high voltage substations, the Shuanglong substation integrated automation system, in addition to achieving conventional monitoring functions, also has the following characteristics: a. The integrated automation system is consistent with the overall layout design of the substation: that is, secondary equipment within the substation is relatively concentrated and installed nearby. The integrated automation equipment is designed according to outgoing line bays or strings, shortening cable lengths, reducing the "antenna effect" of cables in strong electromagnetic environments, and improving control reliability. b. To reduce the possibility of malfunctions caused by interference signals, fiber optics are primarily used as the transmission medium for computer network communication and inter-equipment communication within the substation, and redundancy is employed as much as possible. c. Siemens' 8TK Interlocking Unit is used as the bay-level anti-misoperation interlocking device, forming the substation's hardware interlocking control system. Even if the station's monitoring system fails, complete monitoring and anti-misoperation can still be achieved on the bay-level equipment, ensuring operational reliability. d. The station's monitoring system is equipped with a password authorization system, and the control equipment is divided into units by series or bay on the human-machine interface. After operation prompts and confirmation, the corresponding logic judgment program is initiated for each unit's control operation. After the software checks for correctness, the control command is issued, thus forming a dual detection interlocking function together with the 8TK. e. Important information (such as switch and disconnector positions) uses dual-position contacts (one normally open contact and one normally closed contact), and its legality is judged in both software and hardware. The sequence of events (SOE) resolution reaches 1 ms (as measured on-site by the East China Electric Power Research Institute). f. Transient change signals (such as protection actions and reclosing actions) are processed by software when displayed on the human-machine interface, using a self-holding method. The signal will only disappear after manual confirmation. g. Simulated indicator lights replace conventional indicator lights on the human-machine interface, displayed in a hierarchical mode of full-station and interval levels. Different display methods on the indicator lights are used to distinguish between accident and warning signals. h. The action signals of the microprocessor-based protection system include self-diagnostic information, which is actively sent to the station monitoring system after protocol conversion by the protection management unit. Protection management departments at all levels and dispatch departments can directly retrieve various information from within the protection system via telephone dialing for analyzing the causes and processes of accidents. Operating personnel can remotely retrieve protection information and remotely reset protection action signals through the monitoring system. Hardware (pressure plate) or software methods are used to prevent remote modification of protection settings and the possibility of tripping from the protection device output via communication. i. A relatively independent Automatic Voltage Control (AVC) module is integrated into the comprehensive automation system. It can control the 500 kV system voltage and can also prioritize the control of the 220 kV system voltage. The control target can be a setpoint or a curve; and it has four different operating modes: closed-loop automatic adjustment, semi-closed-loop, L&C, and open-loop guidance. In the software design, automatic interlocking was fully considered in the event of abnormalities and faults in the controlled equipment. This played a positive role in improving the system voltage qualification rate and optimizing reactive power flow. [b]2 Actual Operation Analysis[/b] After more than a year of actual operation, the 500 kV Shuanglong Substation Integrated Automation System has brought considerable convenience to the operation and maintenance of the substation compared with conventional substations, and has played a key role in ensuring the safe operation of the substation. 2.1 Information Acquisition The Shuanglong Substation Integrated Automation System collects a large amount of information from a wide range of sources. In the human-machine interface design, it adopts a variety of methods and means, such as accident audible alarms, flashing position switches, text prompts in the briefing window, analog light boards, and analog quantity over-limit alarms, to ensure that Shuanglong Substation can react quickly, record in detail, and display intuitively when accidents and abnormal situations occur. It retains some traditional operation monitoring habits while changing the monitoring method of operation duty, thus improving the monitoring effect of operating equipment. High-precision AC sampling I/O devices and transmitters are used. Through random sampling and annual calibration tests, except for a very few reactive power measurement points, the overall error was less than 0.5%. The program design allows for easy setting of measurement point limits. Over-limit alarms, in addition to text prompts in the alarm window, also employ multiple prompting methods on the human-machine interface, such as color-changing of analog quantity displays and flashing of corresponding analog quantity values ​​on the analog screen, improving monitoring effectiveness. Since the commissioning of the 500 kV Shuanglong substation, the integrated automation system has withstood five line faults. In each incident, the integrated automation system accurately recorded the entire process of the fault. For example, at 23:57 on April 5, 1998, due to a fault on a 220 kV line at the opposite substation, and multiple grounding points of the voltage transformer (TV) at the opposite substation causing the protection to lose directionality, all three 220 kV line switches from Shuanglong substation to this substation tripped simultaneously. The integrated automation system's warning signal overview table meticulously records 668 records from the start of the 500 kV No. 1 fault recorder at 23:36:51 to the fault clearance at 23:37:35. The event overview table records 73 accurate times and details related to various protection actions and switch trips within 254 milliseconds, from 23:36:51:577 to 23:36:51:831. The microcomputer protection overview table provides the action time, action behavior, and fault location information for each set of line protection systems, providing strong support and assistance for operation personnel in fault analysis, judgment, and timely handling. During trial operation, the 500 kV Lanshuang 5407 line protection multiplexer carrier machine, due to insufficient anti-interference capability, caused false signals. The integrated automation system accurately recorded and reflected this phenomenon, promptly identifying potential safety hazards. 2.2 Control and Operation From December 29, 1997 to December 31, 1998, operators performed 1,042 control operations through the automation system during normal switching operations, achieving a 100% accuracy rate. Additionally, during the commissioning of new equipment, 962 control tests were conducted, also achieving a 100% accuracy rate. Statistical results show that switching operations using the integrated automation system are approximately 10%–15% faster than those in conventional substations, with the operating speed of primary equipment increasing by at least 50%. The main reason for the slower operating speed is the distributed arrangement of relay protection systems, requiring personnel to travel between the relay protection room and the main control room during protection activation/deactivation operations. 2.3 Operation Management and Statistical Reports: The Shuanglong Substation Integrated Automation System replaces conventional manual reports and statistics, automatically generating and printing various daily and monthly load reports, automatically calculating total substation power consumption, voltage qualification rate statistics, switch action and trip count statistics, and main transformer on-load tap changer adjustment count statistics. Furthermore, it can conveniently generate various operation management reports according to the substation's operational needs, significantly reducing the workload of manual meter reading and statistical calculations for on-duty personnel. 2.4 Maintenance and Troubleshooting of Substation Electrical Equipment: Because the Shuanglong Substation Integrated Automation System and protection devices are designed in series or bays, the shutdown of any bay's equipment will not affect other parts, greatly facilitating maintenance and troubleshooting. The integrated automation system clearly reflects the operating status of primary and secondary electrical equipment within the substation, recording and saving the operation, defects, and abnormal conditions of the electrical equipment. Before starting work, maintenance personnel can conduct relevant inquiries to gain a necessary understanding of the equipment requiring maintenance or troubleshooting, such as its current operating status, presence of defects, whether they have been addressed, and any outstanding issues. This ensures that maintenance personnel are fully informed and embodies the principle of "repairing what needs repairing and repairing it well." Relay protection personnel and operation shift workers can use the integrated automation system to check protection settings at any time before and after work, completely preventing "incorrect setting" accidents. On November 18, 1998, after the LFP-902A protection system on Shuanghang Line 2381 was inspected, before the work order was finalized, the shift worker checked the protection settings through the integrated automation system and found a change. It was later determined that the temporary settings set by the relay protection personnel during testing had not been updated in time, thus preventing a "incorrect setting" accident. For some difficult defects, the integrated automation system can be used to further investigate the defect's phenomenon, occurrence time, whether it has disappeared, its frequency, and whether it is widespread. For example, on April 5, 1998, the transceiver (YBX-1K) device of the 901 protection system on the Shuanghang 2381 line malfunctioned. After on-site inspection, the relay protection personnel determined the device was intact and could not find the cause of the malfunction. Through the integrated automation system, it was discovered that the transceivers of the protection systems on three other 220 kV lines had experienced similar issues. The difference was that they automatically returned to normal very quickly after the alarm; the fastest was on the Longyun 2374 line, where only 2 ms elapsed between the malfunction signal and the automatic return. Analysis determined that the problem was caused by interference signals. After implementing corrective measures, similar phenomena did not recur. 2.5 Operational Reliability of Secondary Electrical Equipment In conventional substations, faults in indicator lights, signal panels, and indicating instruments on the control layer account for a large proportion of substation defect handling and also affect the safe operation of secondary equipment. The 500 kV Shuanglong substation, by adopting an integrated automation system, eliminated the conventional control panel, improving the operational reliability of secondary equipment and significantly reducing the number of defect handling operations. Meanwhile, the relay protection devices are distributed in local compartments, which greatly reduces the amount of secondary cables used (according to statistics from the East China Electric Power Design Institute, the savings are approximately 36.6%) and saves on cable investment. More importantly, conventional substations use longer cables, resulting in large distributed capacitance to ground, which often leads to false signals from protection devices, posing significant difficulties for operation and maintenance personnel in analysis, judgment, and handling. However, the 500 kV Shuanglong substation has not experienced a similar situation since its commissioning. [b]3 Suggestions and Discussions[/b] Based on the analysis of the actual operation of the 500 kV Shuanglong substation integrated automation system and the feedback from on-site operators, the following suggestions and ideas are proposed for the substation integrated automation system. 3.1 Improve the reliability of the integrated automation system Improving the reliability of the integrated automation system has always been the fundamental starting point for the development of integrated automation technology. Strengthening the monitoring and control of the integrated automation system itself, including the operating software, is one of the important ways to improve reliability. We believe that although the substation monitoring system has many similarities with the SCADA system in terms of function, their focuses are different. Substation monitoring systems require relatively stable functionality and place high demands on their reliability, security, and stability, particularly in signal processing and equipment control. Due to varying requirements and operating habits across different regions, the application software for substation monitoring systems cannot be completely identical. Simplifying unnecessary non-real-time functions and employing self-diagnosis and self-recovery methods for key operating procedures and internal computer resource management can improve system reliability. 3.2 Expanding the Monitoring Scope of Integrated Automation Systems In addition to reflecting power flow distribution, substation monitoring systems primarily reflect the operating status of primary and secondary equipment. If online insulation monitoring of primary equipment is considered during design and product selection, it is possible to incorporate it into the integrated automation monitoring scope, improving the online monitoring capabilities and scientific management of operating equipment. Furthermore, currently, switching operations of primary equipment, especially disconnectors, still require on-site verification of the equipment's operation and status. Integrating remote computer image monitoring systems with integrated automation systems, utilizing image monitoring to monitor the operating status of equipment, would greatly benefit the improvement of monitoring quality for on-duty personnel and the speed of switching operations. 3.3 Remote Enabling/Disabling and Setting Modification of Microprocessor-Based Protection Currently, enabling/disabling microprocessor-based protection requires operation of the output pressure plate, in addition to modifying the control words in the protection settings. Furthermore, most operating units do not allow remote modification of protection settings. During operation, it was found that the main reason affecting the speed of switching operations is the enabling/disabling of secondary equipment, which requires manual on-site operation (i.e., in the relay protection room). Therefore, remote enabling/disabling of protection and setting modification are necessary for the development of integrated automation. Currently, many experts, scholars, and manufacturers are focusing their research on this area, mainly addressing reliability and management model issues. 3.4 Intelligent Operation Management Under the current on-duty model for all owners of ultra-high voltage substations, improving the level of intelligent management of substations is necessary for power system development and practical operation. Intelligent management of substations is closely related to integrated automation systems, relying heavily on real-time information from these systems. However, in specific implementation, to ensure the safety and reliability of the integrated automation system, it is not advisable to integrate it into the station's monitoring system; it can be a relatively independent system. At present, the intelligent operation management system for substations should include at least the following three parts: a. Based on the information and data collected by the integrated automation system, when an accident occurs in the power grid or substation, it can accurately determine the type, nature, and scope of the accident, and automatically generate accident handling guidance for on-duty personnel, so that on-duty personnel can quickly handle the accident according to the guidance and operating procedures. b. Based on the dispatching orders and real-time information from the monitoring system, it can automatically generate operation tickets online, i.e., it has the function of an operation ticket expert system. c. Based on the substation operation management requirements, it can automatically collect and generate various reports, realizing the computerized management of various operation records and technical data of the substation. [b]4 Conclusion[/b] With the development of science and technology, the realization of integrated automation in ultra-high voltage substations is an inevitable trend in the development of power system technology, and it is also necessary to improve the operation quality and management level of substations. As a pilot project of the former Ministry of Electric Power Industry and one of the first ultra-high voltage substations in China to realize integrated automation, the 500 kV Shuanglong Substation embodies the collective wisdom and hard work of many participating construction units, competent departments, and technical personnel from manufacturers. The functions it currently realizes are also the basic functions of the integrated automation system. It is believed that, based on this foundation and with the continuous efforts of numerous scientific and technological personnel, more comprehensive, intelligent, and complete ultra-high voltage substation integrated automation systems will emerge in my country's power grid construction, raising the safety, stability, and economic operation of the power grid to a new level.