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Development Prospects of Passive Wireless Temperature Measurement Technology

  Power system is a large system composed of many power generation, transmission, substation, power distribution and electrical equipment connected to the failure of power equipment will not only cause unexpected power failure of the power supply system resulting in reduced economic efficiency of power companies, and may result in users Therefore, the reliability and operation status of these equipments directly determine the stability and safety of the whole power system, and also determine the economic benefits and power supply quality and reliability of power enterprises.

  Conduct on-line monitoring of power equipment and analyze the monitoring data by means of various advanced calculation methods so as to detect hidden troubles of equipment in time and take preventive measures to achieve scientific diagnosis and condition maintenance of equipment and reliability of power system operation , Safety is of great significance. With the continuous development and maturity of on-line monitoring technology and the successful application of on-line monitoring technology in China's power system in recent years, the state maintenance alternative periodic maintenance has been accepted by the power system and has become an inevitable trend of equipment maintenance. As early as 2010, SGCC issued Technical Guidelines for On-line Monitoring System of Substation Equipment and began to comprehensively promote the maintenance of equipment status, comprehensively enhance the intelligent level of equipment, popularize and apply intelligent equipment and technologies, and realize the online safety warning and equipment for power grid safety Intelligent monitoring.

  At present, on-line monitoring is mainly based on substation primary equipment, including: capacitance of capacitive equipment, on-line monitoring of dielectric loss; on-line monitoring of full current and resistive current of metal oxide surge arresters; on- UHF partial discharge on-line monitoring, partial discharge casing, on-line monitoring of dielectric loss, on-load switch dynamic characteristics of online monitoring; GIS UHF PD online monitoring, micro-water online monitoring; switch mechanical properties monitoring and sulfur hexafluoride gas Density online monitoring.

  Temperature is an important parameter to characterize the normal operation of a device. Due to the change of hot and cold climate, changes of equipment basis, processing technology, environmental pollution of equipment, severe overload operation, contact oxidation, etc., the pressure is not tight , The pressure is not enough, the contact part of the contact changes, eventually leading to increased contact resistance, the current passed, the temperature increases, resulting in aging equipment, insulation decline, serious can also trigger arc short circuit, burn equipment, expand equipment damage Range, reduce equipment life, and even easily lead to a fire explosion equipment, especially moving knife movement, static contact part of the more serious, high failure rate, which are always threatening the safe operation of power equipment. According to incomplete statistics, many power companies and power generation companies in China such as Guangdong, Shanxi, Zhejiang, Hebei, Sichuan, Liaoning, Gansu and Jiangxi all have varying degrees of substations, enclosed busbars, disconnectors, Cables and other equipment due to aging or poor insulation caused by abnormal temperature changes, which led to the phenomenon of the accident in 2003 Yangquan City, Yuxian 220kv 220kV substation and the northern suburb of Datong 220kv high-voltage isolation switch static and dynamic touch Head due to poor contact with the long-term fever, did not find in time, eventually leading to the movement of contacts burned deformation, causing two major accidents, leading to power outages, direct and indirect economic losses have reached tens of millions. The phenomenon of electric equipment heating has caused the electric operation department attaches great importance.

  At present, most of the temperature monitoring for power equipment adopts the traditional method of measuring the temperature of the wax and the method of measuring the temperature with an infrared thermometer. These two methods have the following problems:

  (1) shows the temperature wax method, easy to aging and fall off, the temperature indicates a narrow range, low accuracy, manual operation, can not be automated management;

  (2) Infrared thermometer can only detect straight line, which is affected by the environment, and can often be obscured and can not be measured.

  (3) The need to conduct regular manual inspection, work intensity, temperature measurement required close, low safety factor;

  (4) Non-online temperature monitoring, can not reflect the process of temperature changes and timely detection of equipment anomalies.

  Therefore, the traditional off-line temperature monitoring method has been unable to meet the requirements of high-efficiency and safe and reliable operation of power generation. There is an urgent need to look for online monitoring techniques to monitor the operating temperature of power equipment on-line and discover the abnormal operating temperature of power equipment in time The situation, to avoid damage to electrical equipment and power accidents. At the same time, on-line monitoring of power equipment temperature to further improve the monitoring of power equipment on-line monitoring of the scope of the status of the electrical equipment maintenance status provides an important parameter to characterize the operation of the power equipment and even the entire power system is of great significance to the safe operation .

  Development Trend of On - line Monitoring Technology for Power Equipment Temperature

  Power equipment temperature on-line monitoring technology generally consists of advanced sensor technology, communications systems, computer and information processing technology, expert analysis system and system data information library. With the continuous development of science and technology, the on-line temperature monitoring technology of power equipment has been moving towards automation, intelligence and practicality.

  Internet of Things technology

  Internet of Things technology is regarded as the next wave of information technology and new technology after computers and the Internet. China has taken Internet of Things technology as one of the emerging strategic industries in the country and made it clear that the Internet of Things will be integrated into the construction of a smart grid . The so-called Internet of things, that is, through the RFID (radio frequency identification) (RFID), global positioning system (GPS), laser scanner and other information sensing devices, the object connected to the Internet for information exchange and communication in order to achieve intelligent identification of objects, Tracking, monitoring and management of a network. The Internet of Things (IoT) has the characteristics of real-time information system and environment comprehensive perception, real-time transmission and sharing of information through network integration and collaboration, and reliable interconnection, and intelligently analyzing and processing vast amounts of perceptual information.

  The Internet of Things architecture for on-line temperature monitoring of power equipment is divided into three layers: perception layer, network layer and application layer.

  The sensing layer collects real-time temperature data of power equipment, and its basic technologies mainly include sensor technology and short-distance transmission technology. Sensor technology mainly uses various temperature sensors, such as contact temperature sensors, infrared temperature sensors, temperature sensors installed directly on the power equipment; short-distance transmission technology needs to consider the isolation of high and low voltage insulation, power equipment for temperature monitoring system, the main use of wireless Communication technologies such as Zigbee communication, 2.4G / 433M wireless communication and so on.

  The network layer supports the information transmission and data communication between the perception layer and the application layer. For the communication between the network layer and the application, in view of the requirements of data security, transmission reliability and data real-time, the information transmission of the Internet of things mainly depends on the communication between the network layer and the perception layer through the wireless communication. Power Communication Network to achieve, mainly to power optical network to power line carrier communication network, digital microwave network supplemented.

  The application layer classifies, synthesizes, transforms, analyzes, decides and shares the collected temperature data of each electric equipment, and the key point is to build an intelligent platform that can provide services for different applications, and can provide various abnormal alarms and trend analysis , Online diagnosis, data sharing and other services.

  The application of Internet of Things technology is the basis for on-line temperature monitoring of power equipment, as well as the reliability, safety and real-time performance of on-line temperature monitoring system for power equipment.

  XY passive sensing technology, replacing battery-powered

  The sensor in the on-line temperature monitoring technology of power equipment is the part that realizes the temperature sensing. The main power supply channel of the temperature sensor using wireless communication is the battery. The temperature sensor usually works under high-voltage and high-current environment, the electromagnetic environment is harsh, which has a big influence on the working life of the battery, and the battery capacity is limited and needs regular replacement and maintenance. In addition, the battery is prone to an explosion accident under high temperature environment, There are certain security risks. Therefore, the power supply of temperature sensor seriously restricts the development of on-line monitoring technology of power equipment temperature.

  With the development of sensor technology, in order to overcome the obstacles caused by battery power supply, passive sensing technology such as electric field pick-up, magnetic field pick-up, RF power supply, temperature difference power supply and SAW technology has emerged as the power equipment Temperature online monitoring sensor technology development, passive sensor technology does not require battery-powered, the obvious advantages:

  (1) The on-line temperature sensor with passive sensor technology can be maintenance-free during the life cycle of power equipment and improve the reliability of on-line temperature monitoring system for power equipment.

  (2) no battery, no high temperature explosion of security risks, high safety; the same time, to continue monitoring of high temperature electrical equipment, allowing users to timely detection of equipment hidden dangers and failures before the accident.

  (3) The application of passive sensing technology can greatly reduce the use of the battery, reduce the pollution caused by the battery and make a contribution to the environmental protection, which has certain social value.

  Point line surface integration, temperature monitoring

  The so-called point and surface combination, the actual is based on the characteristics and importance of different electrical equipment, its use of different temperature monitoring methods, in order to achieve the best solution.

  Point temperature measurement, mainly for the switchgear contacts, bus and cable connection points and other locations, these places prone to temperature anomalies and difficult to monitor by external devices, temperature sensors installed in these places for the purpose of online temperature monitoring .

  Wireless temperature measurement, mainly for high-voltage power cable equipment on-line monitoring of temperature in power plants, substations cable sandwich, cable ditch, large cable tunnel high voltage power cable in the event of overheating can cause fire caused by large area cable burning, resulting in Was forced to shut down, unable to resume production within a short period of time, resulting in major economic losses. At present, the online temperature monitoring of power cables mainly adopts the distributed optical fiber temperature measurement technology. The optical fiber has the technical features of insulation, corrosion resistance, high temperature resistance, immune electromagnetic interference and the like. The distributed optical fiber temperature measurement can realize the temperature of the entire high-voltage power cable Online monitoring, temperature measurement accuracy and high sensitivity, and can locate each temperature measurement point, once the temperature anomalies, can quickly find the point of failure, to avoid fire and other accidents.

  Wireless temperature measurement, mainly for generating units, transformers and other important electrical equipment, the use of infrared thermal imaging technology to achieve the entire equipment temperature monitoring. In 2014, State Grid Corporation of China released the "Notice on Printing and Issuing the Quality Improvement Scheme of On-line Monitoring Devices for Substation Equipment" issued by State Grid Inspection and Quarantine Bureau in 2014, which clearly states that substations should prioritize the infrared inspection of intelligent robots, that is, adopt infrared thermal imaging technology to power Equipment for inspection, infrared thermal imaging technology has an intuitive, comprehensive, efficient, leak-proof technical features that can monitor the overall temperature distribution of electrical equipment to quickly detect abnormal temperature points, provide the basis for equipment maintenance. Due to the high cost of infrared thermal imaging, infrared thermal imaging temperature monitoring is usually performed on important electrical equipment, or periodic inspection is used to monitor the temperature. At present, the State Grid Corporation of China has been in Zhejiang and other provinces to promote intelligent substation inspection robot, a variety of power equipment on the substation periodic inspection.

  Through the combination of the above three temperature monitoring methods, it is possible to fully monitor all kinds of power equipment to the maximum extent and truly achieve dead-end monitoring and provide comprehensive technical support for the safe operation of the equipment.

  Mobile application APP, monitoring device status anytime, anywhere

  With the continuous improvement of the bandwidth of mobile communication networks and the powerful functions of mobile terminal devices such as mobile phones and tablet PCs, especially in the current 4G era, the rise of smart phone applications in general brings us to a brand-new mobile information society. Mobile applications as an important part of mobile information technology, its mobility, convenience, timeliness, personalized features have been widely applied to a variety of business operations management.

  The operation and maintenance of electric power enterprises and many other management and production activities are the core of the healthy operation of enterprises. The good operation of various electric equipment is related to the survival and economic benefits of enterprises. It is also the basic condition for safety production. Device status monitoring information is shared to the mobile application platform via the Internet and the mobile network, and is installed on the mobile phone or tablet to monitor the status of the mobile device APP. With the help of various hardware and software configurations of the mobile phone and the tablet, such as GPS, gyroscope, camera, Two-dimensional code and other technologies, can bring the following benefits:

  (1) Breaking the pattern of the traditional intranet office system, monitoring the status information of the device by the mobile application APP of the power device status monitoring is no longer limited by the time and space, anytime and anywhere.

  (2) For the equipment inspection work, the mobile application APP for condition monitoring of power equipment can conveniently realize recording, photographing and positioning so as to solve the defects of low efficiency, high management cost and inability of personnel to locate in the traditional manual inspection and realize Inspection work of mobile, information technology, intelligent, mobile work management to enhance the efficiency and quality of work.

  (3) Power Equipment Condition Monitoring Mobile Application APP can help personnel quickly locate equipment failure points, view the latest fault conditions and historical data, quickly resolve the fault points, and reduce the power outage time and power failure range in the event of an emergency.

  The application of mobile application APP for condition monitoring of power equipment breaks the limitation of time and space, improves the efficiency and quality of operation and management of enterprises, improves the safe operation of equipment, and is conducive to the healthy operation and development of enterprises.

  3. Conclusion

  On-line monitoring of power equipment status, especially temperature on-line monitoring technology, is one of the core technologies for the future development of smart grid, helping power companies to improve the safe operation level and economic benefit level of power equipment. With the development of science and technology, the on-line temperature monitoring technology for power equipment will develop in the direction of being comprehensive, intelligent and practical. The combination with Internet of Things and mobile applications will be the trend of future development.

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