Abstract: This paper introduces the structure of the automation control system of the 500 kV Shuanglong substation, and analyzes in detail the frequent reset phenomenon of the main transformer and 35 kV equipment main unit. It points out that the excessive amount of information transmitted by the system leads to the overflow of the module buffer, which is the cause of the frequent system resets. Corresponding countermeasures are proposed accordingly. Keywords: Automation; Reset; Computer; Monitoring The 500 kV Shuanglong substation is one of the highest voltage level hub substations in Zhejiang Province. It currently has two 750 MVA main transformers, three 500 kV outgoing lines, and ten 220 kV outgoing lines. It is connected to the Fujian power grid. The 500 kV Shuanglong substation is the first substation in China to eliminate conventional control and adopt full computer operation. It features comprehensive information acquisition, fast response speed, user-friendly human-machine interface, reliable safety anti-misoperation interlocking system, and software-implemented automatic voltage and reactive power control (AVQC) function. It has been operating safely for nearly four years, with stable and reliable operation, and all functions have met the design specifications and operational requirements. After the No. 1 main transformer was put into operation, frequent resets were found in the main transformer and the main unit of the 35kV equipment room. This document provides an overview of the control system and the reasons for these frequent resets. 1. System Structure The 500 kV Shuanglong substation control system adopts a hierarchical distributed structure, configured according to electrical units. It can be broadly divided into two parts: the substation layer and the bay layer. The substation layer system consists of dual main units, dual HMI workstations, a main and backup communication unit, a protection management unit, and a protocol converter interconnected via dual fiber optic Ethernet. The HMI workstation displays real-time information on dual CRTs and transmits relevant real-time information to an analog screen for intuitive display via an RS-232 serial communication port, facilitating observation by operators; it also provides a human-machine interface for operators to perform various operations. The system uses a UNIX operating system, X-Windows, a Motif user interface, and the TCP/IP communication protocol. The protection management unit, protocol converter, and related equipment are installed in the local relay protection room. In addition to direct cable connections to the protocol converters in their respective compartments, the main units of the 500 kV and 220 kV systems are also connected via optical fibers to the protocol converters in another compartment of the same voltage level, enabling mutual backup of the protocol converters and increasing system reliability. Each compartment's main unit aggregates its information and transmits it online in real-time via the protocol converter, achieving information sharing. The LFP901 and LFP902 microprocessor-based line protection devices for the 220 kV lines and the DLP, DFP, and DLM microprocessor-based protection devices for the 500 kV lines transmit information online through their respective protection management units. The main unit aggregates and processes the information to achieve the required functions. The main and backup communication units transmit relevant information from the substation in real-time to the East China General Dispatch Center, Zhejiang Provincial Dispatch Center, and Jinhua Regional Dispatch Center, enabling all levels of dispatchers to monitor the operation of the 500 kV Shuanglong substation. The 500 kV and 220 kV bay-level equipment is installed in local relay protection rooms and consists of a 6 MB monitoring and control system, a 7 VK synchronizing device, and an 8 TK electrical interlocking system. The 6MB551 monitoring and control device is the main unit of each bay-level room, communicating with each 6MB522 I/O unit via a fiber optic star network. It also uses Siemens' 8FW protocol and protocol converter for communication and achieves main unit time synchronization via GPS. The 7VK is used as a synchronizing device, configured entirely according to switch specifications. It has various synchronizing methods and is easy and flexible to set. The 8TK is an important component of the electrical operation safety anti-misoperation interlocking system for switches, isolating switches, and grounding switches. 8TK1 is an electrical unit operation control interlocking device, capable of collecting the status of up to 14 devices per unit. 8TK1 itself can complete the interlocking logic judgment of its bay and realize equipment control. 8TK2 is the main unit of the electrical operation interlocking system, also capable of collecting the status of 14 devices and realizing control, generally used for status acquisition and control of busbar equipment. Once the status of the equipment involved in the control is collected by the other 8TKs, 8TK2 communicates with the relevant 8TK1 and the other 8TK2s via a double-shielded four-core cable to collect the operating status of the relevant equipment. It then performs a station-wide interlocking logic judgment according to the prescribed interlocking logic and returns the judgment result to the 8TK1 or 8TK2 currently in operation. The main transformer and 35 kV equipment room automation equipment is installed in the 35 kV protection room of the main control building. It is mainly configured with one main unit 6MB551 and twelve I/O units 6MB522. The main unit configuration includes: one FP module, one SK module, one BA module, one BF module, five AR modules, six DE modules, and two RK modules. The main transformer and 35 kV equipment room automation block diagram is shown in Figure 1. The status of circuit breakers, isolating switches, and grounding switches is directly sent to the relevant I/O units via dual-position contacts. Their operation control is achieved by the I/O units directly outputting contacts. The tap changer adjustment of the main transformer is achieved by the I/O units. The auxiliary transformer is not equipped with a corresponding I/O unit; its contact signals are directly connected to the DE module of the main unit. The tap adjustment of the auxiliary transformer is also implemented by the BA module of the main unit. Analog quantities such as power and current of capacitors, reactors, and the 35 kV side of the main transformer are acquired by the 6MB522 I/O unit. Analog quantities such as main transformer temperature and auxiliary transformer voltage are converted by transmitters and then connected to the AR module of the main unit. Electricity pulse quantities are output from the pulse electricity meter to the DE module of the main unit. The analog quantities acquired by the AR module are processed through thresholding and zero-bias suppression before being transmitted to the FP module via SINAUTLSASYSTEMBUS. Analog quantity transmission is divided into two types: automatic transmission over thresholds and FP module scanning transmission. The switch quantities of public equipment and electricity pulse quantities are acquired by the DE module and processed through status comparison and counting before being transmitted to the FP module via SINAUTLSASYSTEMBUS. The tap adjustment commands of the auxiliary transformer are also issued from the FP module to the BA module via SINAUTLSASYSTEMBUS. Each I/O unit is connected to the SK module of the unit via serial communication. The main unit exchanges information with the SK module by directly reading and writing the dual-port RAM on the SK module through SINAUTLSASYSTEMBUS, thereby realizing information exchange between each I/O unit and the FP module. 2. Analysis and Handling of Frequent Resets of the Main Unit of the Main Transformer and 35 kV Equipment After the main transformer and 35 kV equipment had been in operation for a period of time, the on-duty personnel found that DC over-limit alarms and other signals frequently occurred. Subsequently, they discovered that the analog quantities collected by the main unit were all "0". After carefully checking the operation of the automation equipment, it was found that during the operation of the automation equipment, the "H4" light of each AR module was frequently lit for a long time, unlike the normal "flashing" state. All other indicator lights on the equipment were normal. After running for a period of time, the main unit would reset. By replacing AR, DE, BA, BF, SK, RK, SV, and FP modules for inspection and testing, it was confirmed that none of the functional modules were damaged. After reinstalling the system program and parameterization files, the reset phenomenon still existed. The "H4" indicator light of the AR module indicates that the AR module's analog quantity exceeds the threshold and the spontaneous transmission time is relatively long. After observation and analysis using LSADIAG diagnostic software, it was found that the ring buffer of AR module No. 2 frequently overflowed, and other AR modules also had the same phenomenon. Before the No. 1 main transformer was put into operation, the automation equipment of the main transformer and 35 kV equipment room was responsible for the acquisition of analog quantity, switch quantity, and pulse quantity of one main transformer, two sets of capacitors, two sets of reactors, and two auxiliary transformers, as well as the control operation of related equipment; the threshold of analog quantity was set to 0.1%; the priority order of information transmission was: (1) switch quantity change information. (2) pulse quantity information once every 5 minutes. (3) full telemetry and full telesignal information once every 10 minutes. (4) analog quantity information. (5) event sequence record. (6) local monitoring information once every 15 minutes (this information can be connected to the computer through the RS232 port for debugging). (7) information on equipment control operation is inserted and transmitted. After the No. 1 main transformer was put into operation, the main transformer and the 35 kV equipment room automation equipment were responsible for the acquisition of analog, switch and pulse quantities of 2 main transformers, 4 sets of capacitors, 4 sets of reactors and 3 auxiliary transformers and the control operation of related equipment; the priority order and threshold of information transmission remained unchanged. Compared with the No. 1 main transformer before and after its commissioning, the amount of information collected by the automation system increased by more than double, especially the analog quantity; the analog quantity changed frequently, coupled with the small analog quantity threshold and the unreasonable priority order of information transmission, the data exchange was too frequent, which made the data transmission load of the system bus large; resulting in abnormal information transmission, the AR module ring buffer frequently overflowed, and the main unit of the automation system was frequently reset. Based on the above analysis, we started to reduce the data exchange load from three aspects to ensure that the analog quantity information can be transmitted normally and orderly. (1) The accuracy index of the analog quantity measurement of the automation system is 1.5%, while the original analog quantity threshold is 0.1%. The higher accuracy increases the analog quantity beyond the threshold to transmit information, which increases the communication load. Therefore, the threshold of the analog quantity defined by the AR module was increased from 0.1% to 0.5%, which greatly reduced the spontaneous data transmission of analog quantities between the AR module and the FP module; at the same time, the information flow sent by the FP module to the protocol converter was reduced, thereby reducing the communication load. (2) The local monitoring information once every 15 minutes that is not related to the normal operation of the automation system was deleted, reducing the operating load of the automation system and making full use of system resources. (3) On the basis of the information insertion transmission of equipment control operation, the priority order of the other information transmission was reasonably adjusted, and the information transmission priority was set as follows: 1) Switch quantity change information; 2) Analog quantity information; 3) Pulse quantity information once every 5 minutes; 4) Full telemetry and full teleindication information once every 10 minutes; 5) Event sequence record. After the above measures were taken, no reset phenomenon has occurred so far, all technical indicators meet the requirements, and the main transformer and 35 kV equipment room automation equipment are operating normally. 3 Conclusion This article analyzes the causes, mechanisms and solutions of the frequent reset phenomenon of the 500 kV Shuanglong transformer main transformer and the 35 kV equipment main unit. The automation equipment in the other four small rooms of the 500 kV Shuanglong substation also has the same problem. The reason is that the configuration of the automation system did not fully consider the information scale under the long-term construction of the substation, and the processing of automation information was improper. Considering the construction of substation automation, regardless of the product used, the configuration of the automation system, the information access during the expansion of the substation, and the rationality of the information processing process should be fully considered. At the same time, in order to make full use of the limited resources of the automation system, functions that are not related to the normal operation of the automation system and that are not conducive to the safe, economical and stable operation of the power system can be cancelled. References: [1] Zhang Shaohua, Chen Weizhong. Operation analysis of integrated automation system of Jinhua 500 kV substation [J]. Automation of Electric Power System, 2000 (24). [2] Siemens. Operating Instruction [M]. Siemens, 1995.