Summary:To save labor costs and improve the monitoring conditions in coal mine shafts, reduce errors in manual monitoring, and enhance the intelligence and automation of the monitoring system, wireless temperature sensing sensors are utilized to monitor the working environment inside the high-voltage and low-voltage switchgear cabinets underground. The designed wireless temperature monitoring system can perform real-time and accurate monitoring and early warnings, significantly boosting efficiency. It also features zoning localization capabilities, making fault early warnings clearer and prevention and control more effective. The system continuously monitors and issues early warnings for key temperature locations in the switchgear cabinets of the underground substation, enhancing safety and production guarantees for coal mines.
Keywords:Underground high and low voltage switches; internal contact temperature; prediction of high-temperature point location; contact-type temperature sensor
0 Introduction
Substations are crucial power supply equipment in coal mines, and their performance directly impacts the normal production and safe operation of the mine. Therefore, it is necessary to implement real-time online monitoring of the substations to promptly detect any faults and facilitate timely repairs.
Current measures in coal mines involve manual inspections, relying on inspectors using handheld infrared thermometers to check equipment temperatures. This requires manual operation and cannot achieve real-time monitoring. Therefore, the adopted maintenance method is regular inspections and replacement of components. For power supply equipment with moderate loads, this maintenance method can be employed. However, for equipment failures caused by abnormal overheating due to high loads, according to analyses by experts in related fields domestically and internationally, predictive maintenance is a suitable method for such equipment. The wireless online monitoring system can perform real-time online temperature monitoring at monitoring points, displaying current temperatures in real-time. It analyzes data to predict fault trends and temperature change rates, saves and analyzes historical and abnormal data, and can trigger timely alarms when temperature limits are exceeded, accurately providing fault locations for cables, contacts, and other components. This is an important approach to implementing predictive maintenance.
Underground High-Low Voltage Switch Wireless Temperature Measurement System Solution
1.1 System Composition
The underground high and low voltage switch wireless temperature measurement system includes explosion-proof temperature measurement hosts for mining, wireless temperature sensors, and on-surface system monitoring hosts.
In consideration of the underground working environment, the temperature measurement master unit is explosion-proof, enabling multi-channel light conversion. To provide a clear understanding of its operational status, various warning indicator lights are set up, offering higher system accuracy and stronger resolution. It provides multiple interfaces such as network port, serial port, and USB, allowing the monitoring data to be transmitted through the existing communication and monitoring network on the mine to the ground for remote monitoring.
The temperature sensors we use have short response times, high monitoring accuracy, and a reasonable structure, effectively ensuring the stable operation of the system. The relevant technical parameters of the system are shown in Table 1.
1.2 Target of Plan 2
For the temperature conditions of the 90 high-voltage distribution units (totaling 540 points) at the Wujiazhang Power Distribution Room, Second Central Power Distribution Room, Zhangba Three District Power Distribution Room, Hongjian沟 Power Distribution Room, Fourteen Mining Area Power Distribution Room, Thirteen Mining Area Power Distribution Room, Auxiliary Track Tunnel Power Distribution Room of Area Three, and Yangpo Yan Power Distribution Room of Yangquan Coal Group, a real-time online monitoring and early warning system has been implemented, along with predictions and forecasts for hot spots.
1.3 System Architecture and Features
The system boasts strong resistance to electromagnetic interference and can adapt to monitoring equipment temperatures in harsh electromagnetic environments. The application of digital sensing and communication technology further enhances the system's centrality. The systems are clearly分工ed, closely collaborating to ensure the stable operation of the system, as illustrated in Figure 1.
System Features: ① The temperature sensors are installed in environments with high voltage, strong electromagnetic interference, and high sealing, featuring high insulation and resistance to electromagnetic interference. To facilitate usage and maintenance, the sensors also boast low power consumption, high-temperature resistance, simple installation, and long service life. ② Utilizing data analysis technology, the system achieves storage and querying of historical data, comparative analysis, trend analysis, and diagnostics. It can automatically alert to abnormal events in equipment and make certain fault judgments. ③ This system can be integrated with monitoring systems in power distribution rooms, remote monitoring centers, and security monitoring systems, among other subsystems, enabling联动operation. It constructs an information communication and sharing platform among devices. ④ The system employs the latest wireless sensor technology to implement a safe temperature monitoring system for coal mine substation transformer stations, reflecting the monitoring status of the transformer station on a single interface for real-time online monitoring and analysis. Data is transmitted via MODBUS bus networks, Ethernet, wireless WiFi, GPS, and other methods, facilitating connection with existing automation systems.
1.4 Project Implementation Plan
Yangmiao Coal Mine's underground high-voltage switchgear temperature measurement project involves 8 power distribution rooms with a total of 8 temperature measurement hosts. The specific distribution is as shown in Table 2.
Installation Methods and Positions for the 1.5-Sensor
The system employs a wireless temperature sensor using the LTU32 passive UHF RFID temperature sensing chip. Compared to traditional temperature sensor chips, it is more environmentally friendly, featuring identity recognition, real-time transmission of location information, and data detection capabilities.⑥ Its unique internal circuit design ensures enhanced stability in high-temperature environments, making it adaptable to the complex underground coal mine working conditions, thereby providing guarantees for coal mine safety and efficient production.
Based on the on-site conditions and for the convenience of later maintenance of the distribution panel, the installation design of the sensor is considered to be removable. The sensor is securely adhered to the surface of the moving contact using epoxy resin adhesive. This method not only accurately measures the real-time temperature of the load phase but also facilitates equipment maintenance without damaging the sensor.
2 Application Scenarios
In line with the objectives set by the research and development projects, extensive application trials have been conducted, verifying each pre-determined function individually.
The system monitors and controls the high-voltage switch in the underground power distribution room of Yangmei Group's mine. Temperature measurements are taken for both low and high-voltage switches, with primary measurement points located at the contact points between the switch body and housing (i.e., the static and dynamic contact surfaces), switch output cable heads, and switch busbar connections, among others. The monitoring scope includes the power distribution rooms at Hongjian沟 (14 switches), Wujiazhang (14 switches), Yangpo Yan (12 switches), Shisi Mining Area (12 switches), Shisan Mining Area (12 switches), Zhangba Sanqu (8 switches), Sanqu Auxiliary Track Tunnel (6 switches), and Erzhong Central Power Distribution Room (12 switches). This totals to 540 temperature measurement points, 90 sensors, and 8 temperature measurement hosts. One temperature measurement host is placed in each power distribution room, with real-time switch cabinet temperature data transmitted from the hosts to the surface service end via the underground ring network. The service end monitors, records, and analyzes the temperature of switch cabinets in each underground power distribution room in real time.
The underground high and low voltage switch wireless temperature measurement system can continuously measure various temperature points for 24 hours. Staff in the ground control room can set the high-temperature alarm limit for the temperature measurement system. When the detected equipment exceeds the set temperature value, the system can automatically issue a warning (notifying the dispatch staff that the power equipment associated with this switch shows signs of overload when the temperature exceeds 60℃), an alarm (producing an alarm signal to notify the dispatch and relevant staff that the load has exceeded its limit when the switch temperature exceeds 90℃), and store this information in the database. Staff can then visit the fault location (switch) in advance to inspect it on-site and take appropriate measures to prevent accidents.
Through trial operation, temperature monitoring at critical positions within high and low voltage switchgear has been achieved, preventing accidents such as switch tripping and burning due to overheating in advance, thus enhancing the reliability of the underground power supply system.
The temperature measurement system features include: 1. Alarm function. Over-temperature alarms and unbalanced temperature alarms for phases A, B, and C at the same location. Over-temperature alarms have two levels: early warning and alarm, with alarm limits set by the user. 2. System interface display. Shows temperatures and alarm information at each point on a single system diagram. The system's temperature sensors upload temperature data regularly (e.g., every 1 to 30 minutes). 3. Historical data query. Selectable types of historical data to query, including historical curves, historical values, and monthly highest temperatures. It also allows for on-the-spot temperature data query for any temperature measurement point, along with the year, month, and day of the query. The database can store at least 1 year of historical data, and it can query the most recent 1 month of historical data for each temperature point, with ease of exporting to Excel spreadsheets. 4. Real-time temperature monitoring display. Draws real-time temperature curves for each monitoring point, enabling both graphical and list analysis of temperature data. 5. Temperature measurement data can be transmitted and shared remotely. It can be integrated into the comprehensive automation system, integrating temperature data, centralized display, and alarms. 6. Fault alarm and record query (can be queried based on fault type, time, location, etc.).
3 Application Scenarios
Temperature monitoring suitable for power equipment in enterprises such as ubiquitous power Internet of Things, steel mills, chemical plants, cement factories, data centers, hospitals, airports, power plants, coal mines, and transformer substations.
Version 4 System Architecture
Structure Diagram of Temperature Online Monitoring System
5 System Features
The Acrel-2000T temperature monitoring system is installed in the duty monitoring room, enabling remote monitoring of the operating temperatures of all switchgear within the system. The system features the following main functions:
- Temperature Display: Shows the real-time values of each temperature sensing point within the power distribution system, and allows for remote data viewing via computer WEB or mobile APP.
- Temperature Trend Curves: View the temperature trend curves for each temperature sensing point.
- Operational Report: Query and print temperature data at specified times for each temperature sensing point.
- Real-time Alerting: The system can issue alerts for abnormal temperatures at various temperature sensing points. It features real-time voice alarm capabilities, enabling voice alerts for all events. The alert methods include pop-ups, voice alarms, and can also send SMS or APP push notifications to promptly remind on-duty personnel.
- Historical Event Inquiry: Capable of storing and managing records of events such as temperature limits exceeded, facilitating users in tracing historical system events and alarms, and conducting inquiries, statistics, and accident analysis.
Conclusion
Traditional power sensing and monitoring systems are primarily based on electronic sensors, which have low reliability, cannot be displayed online in real-time, and are prone to environmental temperature, humidity, and electromagnetic interference, leading to drift and poor repeatability and long-term stability. Therefore, the current wireless temperature sensing technology is adopted to realize real-time online temperature monitoring in coal mine power substation. Compared to traditional power sensing and monitoring systems, this system offers the following advantages: 1) The system uses passive sensors to detect temperature information, ensuring inherent safety and high stability; 2) The temperature information is transmitted through wireless signals, immune to electromagnetic interference and moisture-proof; 3) The system has a shorter response time, a wider monitoring range, stronger ability to adapt to harsh working environments, higher sensitivity, and improved system stability and reliability; 4) The system is well-designed, occupies minimal space, is easy to install on-site, has a broad monitoring and early warning range, and excellent radiation and electromagnetic interference resistance; 5) The system can perform single-wire multi-point measurements, with a large capacity and strong reuse capability.
References
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