Discussion on 220KV Intelligent Unmanned Substations

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How to save on labor costs and management costs. . . . How to visualize substation management to improve operational efficiency and reduce operation and maintenance costs. Construction Plan for an Intelligent Inspection System for Substations – Shi Haijian I. Analysis of the Current Situation of Manual Inspection in Substations (1) Content, methods, frequency, and requirements of manual inspection In accordance with the guidelines and requirements set out in the \"Substation Management Standards for Power Grid Companies\", the \"Management Standards for Unmanned Substations (Trial Version)\", and the \"Standards for the Management and Maintenance of Substation Equipment in Power Companies\", as well as considering our company’s current situation. As the company grows rapidly, there will be a severe shortage of electrical personnel. At the same time, not many young people are willing to enter this industry. Under these circumstances, the workload of existing electrical workers is increasing steadily. There are a large number of devices under their responsibility, and the coastal climate is characterized by frequent severe weather conditions, which creates significant safety risks for those who conduct night inspections of various MCCs ； Manual inspections have limited effectiveness and low efficiency. The current inspection methods rely heavily on human effort, and the skill level of electrical personnel directly affects the effectiveness of the inspections ； Due to limitations in the viewing angle, manual inspections lack comprehensiveness, and the work efficiency of personnel is relatively low ； 1. Substation equipment inspections are divided into regular inspections (including shift handover inspections), comprehensive inspections, dark-inspection tours, and special inspections; records should be kept for each type of inspection. Ø Normal inspections (including those during shift handovers): In addition to complying with relevant requirements, manned substations must also carry out thorough inspections of the equipment during shift handovers, which must be completed within the specified periods and time frames. Unmanned substation: Once a day at the stations under the centralized control station ； Stations under other central control stations are inspected once every 2 days. Ø Turn off the lights for inspection: Check whether there is corona or discharge in the equipment, and whether the connections are overheating and turning red. For substations with personnel on duty, the inspection should be carried out once a day; for those without personnel on duty, it should be done once a week. Ø Comprehensive inspection (standardized operational inspection): It involves a thorough external examination of the equipment, assessment of whether any defects are progressing, identification of the equipment’s weak points, inspection of the anti-misoperation locking devices, and verification that the grounding grid and connections are in good condition. Unmanned substations are inspected twice a month, once in the first half of the month and once in the second half. Ø Special inspections: To be determined based on specific circumstances. Special inspections should be conducted in the following situations: before and after strong winds ； After the thunderstorm ； Snow, hail, foggy weather ； After the equipment change ； After the equipment is put into operation for the first time ； After the equipment has been overhauled, modified, or restarted after a long period of shutdown ； Equipment abnormalities ； When equipment defects develop ； Legal holidays, periods of critical power supply tasks, etc. During statutory holidays and periods with important power supply maintenance tasks, each unattended substation must be inspected at least once per day. 2. During this period, in addition to regular inspections, special equipment inspections and infrared temperature measurements will be carried out. Unmanned substations are inspected once a day. Infrared temperature measurement is divided into three types: normal infrared temperature measurement, hot spot tracking temperature measurement, and infrared temperature measurement of critical equipment during special periods. Ø The normal infrared temperature measurement cycle is at least once per week at each substation, during the evening peak hours. Mainly targeted at equipment under long-term heavy loads ； When the equipment load increases significantly ； The device is showing abnormal behavior and overheating; further analysis and assessment are required ； When there are clear requirements from higher authorities, such as ensuring power supply during special periods. Ø Heat source tracking temperature measurement should involve comparing the heat generation levels based on the measured temperature, load current, ambient temperature, and climate changes, in order to analyze variations in the equipment’s heat sources and determine the nature of the heat generation. Its cycle is once a day at manned substations, during the evening rush hour. For unattended substations, inspections are carried out once per inspection day, or once daily by the shift supervisor depending on the heating conditions. Ø During special periods, comprehensive temperature monitoring, targeted temperature checks, and tracking of areas with high temperatures should be carried out. Temperature measurement records should be comprehensive, and should mainly include information such as the operating number of the equipment that generates heat, a detailed description of the location where heat is generated, the temperature at that point, the temperature of similar locations on the same phase of this equipment (or of similar locations on equipment of the same type), the magnitude of the load current, the time of temperature measurement, weather conditions, and ambient temperature. (II) Analysis of the effectiveness of manual inspections: Substation operators carry out manual inspections, making simple qualitative judgments about the operating equipment based on their senses, primarily through sight, touch, hearing, smell, and other sensory methods. Manual inspection can detect defects that are visible, audible, or odorable on the outside of the equipment; these include things such as oil level, oil temperature, pressure, oil leaks, external damage, rust, smoking, fires, unusual odors, abnormal noises, and abnormal indications from auxiliary equipment. Manual inspections are greatly influenced by factors such as an individual’s physical and mental conditions, sense of responsibility, external working environment, work experience, and skill level; as a result, there is a possibility of missing inspections or failing to detect defects. Moreover, regarding defects inside the equipment, operators lack professional instruments or the precision of such instruments is too low; simple visual inspections cannot detect them, such as excessive levels in oil and gas tests, overheating in certain parts of the equipment, and insufficient insulation quality ； There is also another type of defect that can only be detected during operation, such as mechanical jamming, improper opening and closing of the cutters, and damage to the door of the cutter mechanism box. On the other hand, with the increase in unattended substations and the greater distances between many of them, when an accident occurs inside a substation or when strong winds, heavy snow, or thunderstorms prevent dispatchers at the control center from going to the site for inspections, the operators at the control center are unable to promptly understand the status of the equipment on site or identify potential hazards, which endangers the safe operation of the power grid. In particular, it is not possible to promptly understand the situation of the substation where a problem has occurred, thus losing the opportunity to prioritize handling it. When inspecting equipment, inspectors must stand relatively close to it, which poses a certain threat to their personal safety. The risk is even greater when examining abnormal conditions, conducting special inspections during severe weather, or determining the causes of accidents. In summary, manual inspections in unattended substations suffer from poor timeliness and reliability, require a significant amount of labor, involve considerable traffic risks and risks during the inspection process, and result in low inspection efficiency. II. Conditions required for carrying out intelligent inspections (I) Current status of equipment and personnel at the centralized control station: 1. The comprehensive substation automation system and centralized control station management model are fully implemented. 2. Transformer-based devices are of the electromagnetic type, with analog signals; digital monitoring of the oil level is not possible. 3. The locations of primary equipment (with the exception of the switch position signals for 35 kV and below) are already under backend monitoring; functions such as measurement by secondary equipment, detection of fault protection abnormalities, and device operation signals are also available. However, comprehensive real-time video monitoring has not been implemented, and there is a lack of monitoring for equipment conditions such as overheating, leakage, and oil level. (II) Current status of the information and communication network: The information and communication network in substations uses separate optical fibers, which are connected directly through network switches. The network bandwidth is as high as gigabit, ensuring stable operation and meeting the requirements for intelligent inspection of substations. III. Intelligent Inspection Plan for Substations (I) Construction Objectives and Approaches: In the substations under the control of the centralized control station, by installing systems such as video surveillance, infrared pan-tilt temperature monitoring, switchgear temperature monitoring, online chromatographic monitoring of transformer oil, SF6 density and moisture level monitoring, online monitoring of the operating characteristics of high-voltage switches, environmental monitoring in high-voltage rooms, online monitoring of arresters, online monitoring of DC systems, remote control of lighting systems, and protection information management systems, an intelligent inspection management platform for substations can be established. This platform integrates information on the operational status of equipment as well as video footage, thereby enabling visual and intelligent inspection of substations. The goal is to extend the inspection intervals or even replace manual inspections. 1. Remote visualization of on-site equipment Ø Routine inspections: In accordance with the pre-set inspection sequence, operators can view the information from the automatic rotation of various cameras at the main station; both automatic and manual inspection modes are available, and the lighting is activated automatically during night inspections. Ø Professional inspection: Check the pressure value, oil level, humidity in the high-voltage chamber, and temperature of the main transformer of the equipment in sequence. Ø Special inspections: Depending on weather conditions and equipment operation status, it is possible to freely choose or set up inspections for certain equipment. Ø Inspection with lights off: Conduct inspections using video and infrared temperature measurement systems to check for any discharge or heating in the equipment. 2. Real-time collection of equipment operation status information: Various online monitoring technologies and methods are used to collect in real time data such as the equipment’s temperature, oil chromatography results, SF6 gas density, switch operation characteristics, arrester leakage current, and the conditions in the high-voltage chamber; it also features an automatic alarm function for any data that exceeds the specified limits. 3. Auxiliary equipment can be remotely activated to turn on the substation lighting system from a distance. 4. The intelligent inspection management platform builds on the company’s existing comprehensive online monitoring system for substations by integrating video surveillance systems; it combines the image information and operational data of equipment on a single screen, enabling unified monitoring of both the external appearance and internal operating conditions of the equipment. (II) Subsystem development plan 1: Principles for deploying industrial-grade video surveillance systems: Ball-shaped cameras should enable clear visibility of the operating parameters of various key equipment in the substation, such as the readings on switches and instruments, as well as the oil level of the main transformer. 220KV equipment area: Monitor SF6 gauge pointer readings, rheological conditions, switch status, equipment appearance, oil level of the main transformer, etc ； 20KV 10KV equipment area: Monitor the status of switches, the appearance of equipment, the oil level of the main transformer, etc. 2. The temperature monitoring system for switchgear uses fiber optics to carry out real-time monitoring of the operating temperatures at the moving contacts and busbar connections within the switchgear. It monitors the temperatures of the upper and lower contacts on each of the three phases of the switch, and each monitoring device can receive? The signal from a temperature sensor. 3. The infrared pan-tilt temperature measurement system adopts the standard of installing an infrared imager in 220kV substations and one infrared imager in 110kV substations, thereby monitoring the changes in the operating temperature of the equipment via remote control. Alternatively, by setting the parameters of the monitoring platform, the temperature of the equipment can be automatically monitored, with the monitoring data and infrared images being saved automatically. Installation location: The location shall be determined based on the actual conditions on site; the diagram below shows an example of an infrared imager that has been installed. 4. For the online monitoring of moisture and density in SF6 gas, Finnish Vaisala moisture sensors are used to measure the water content in the SF6 gas within SF6 circuit breakers or GIS units; at the same time, the temperature, pressure, and density of the SF6 gas are also measured. 5. Online monitoring of circuit breaker operating characteristics: The online monitoring system for circuit breaker operating characteristics uses specialized Hall current sensors to collect waveform and data related to the operation of the circuit breaker’s opening and closing coils, as well as the energy storage motor. It also collects waveform and data of the current sensed by the secondary side of current transformers. The sampled data is then processed and analyzed through the circuit breaker monitoring terminal, and transmitted via the RS485 bus to the backend comprehensive online monitoring software. Users can easily view the waveform of the opening and closing coils, the operating status of the energy storage motor, as well as the software’s evaluations and analyses of the circuit breaker’s operating conditions. 6. Online chromatographic monitoring of transformer oil: Install online chromatographic monitoring systems for all main transformers, in order to achieve comprehensive, real-time, on-line monitoring of the dissolved gas content in the transformer oil (consider whether sharing these systems is possible). 7. Environmental monitoring in the high-voltage chamber: When electrical equipment in the high-voltage chamber experiences overheating, short circuits, or flashover faults, it is often possible to detect smells of burning, flames, as well as odors emitted by heated plastics, rubbers, paints, and other materials. Gas sensors are used to monitor the gas components in the air in real time; when there are changes in the composition of the air, these sensors send alarm signals to the monitoring device, and the data from these alarm signals is transmitted to the main station of the intelligent inspection system. When a device malfunctions, it will produce noise, and there may even be crackling discharge sounds. By using noise sensors to monitor changes in volume when the device is operating normally versus when it is malfunctioning, it is possible to detect device failures. Taking the acoustic environment conditions in the high-pressure chamber as the monitoring target, sensor technology and network technology are utilized to create an automatic monitoring system for abnormal sounds in the event of equipment failure. 8. Online monitoring of arresters enables real-time monitoring of the arrester’s leakage current (total current and resistive current) as well as the number of times it operates. 9. Online monitoring of the DC system enables effective monitoring of parameters such as the internal resistance of individual battery cells, floating charge current, floating charge voltage, and insulation parameters relative to ground, through the use of cell voltage and internal resistance testers as well as insulation monitors. 10. The remote control of the lighting system enables remote control of all lights in the controlled stations; the central control station can remotely turn on and off the lights in the controlled substations. 11. The protection information management system enables real-time viewing of AC sampling values of substation protection devices, protection action events, abnormal messages, and the status of soft pressure plates, all through the installation of a protection information management unit. 12. Intelligent inspection management platform: The intelligent inspection management system integrates various types of online monitoring systems, video surveillance systems, protection information management systems, as well as substation fire and theft prevention systems. It has the following functions: (1) The camera automatically patrols in a set sequence and at a set speed ； (2) During manual inspections, the equipment’s technical parameters, operating status, and video image information can be displayed collectively ； (3) Alert when the equipment is operating abnormally.