Theoretical Analysis And Experimental Study Of The Wireless Temperature Measurement System Based On Surface Acoustic Wave

Temperature is one of the important signs to identify the states of the electrical equipment. With the temperature as a basis for the assessment of states of the electrical equipment and operation to respond, the failure and fault of the electrical equipment can be detected. Thus it is important to monitor the temperature of the electrical equipment. Due to limitations and deficiencies of the temperature measurement technology used in power systems nowadays, a new solution of temperature measurement-Wireless temperature measurement system based on SAW (surface acoustic wave) has significant advantages for its wireless and passive characteristics, which can realize the online real-time temperature measurement of the electrical equipment. Since the study and application of the system is still at an early stage, the theory and operating experience is not mature, based on which the author carried out the theoretical analysis and application research on the wireless temperature measurement system based on SAW.This paper describes the technical feature, operational principle and components of the system. The system combines the SAW technology with the radio frequency identification technology, consisting of SAW temperature sensor, reader and temperature monitoring software. Because the SAW sensor communicates with the reader antenna by high-frequency electromagnetic wave at433MHz, electromagnetic wave propagation characteristics and electromagnetic environment will affect the system.The paper replaces the switchgear cabinet by metal cabinet and experiments on the effects of space forms on the SAW temperature measurement are conducted. In the open space and the closed space of the metal cabinet, experimrnts of the effects of the polarization direction and metallic objects on reading range between the reader antenna and the sensor are conducted. It is concluded that the polarization direction of the antenna and the metal objects have less influence on the performance of the temperature measurement system in the closed closed space of the metal cabinet, and thus the wireless temperature measurement system based on SAW is more suitable for measuring the temperature in the metal cabinet like the switchgear cabinet.The paper focuses on the electromagnetic interference of the bad electromagnetic environment with the system in high-voltage electrical equipments. When corona discharge, arc discharge, partial discharge and electric fast transient in the electrical equipment occur, they usually produce an electrical pulse or pulse groups, radiating electromagnetic waves. The paper analyzes the characteristics of the frequency domain of corona discharge; models the corona discharge as a dipole antenna; studies its radiation characteristics by simulation by Matlab. Based on this, the experimental platforms of wire corona discharge and short-gap arc discharge are set up. The results of the experiments confirm that corona discharge and arc discharge cause electromagnetic interference to the system and the influence decreases as the distance between the sensor and discharge sources increase.The sensor should be kept a certain distance from the discharge sources. In the end, simulation analysis of the time domain of partial discharge and the radiating characteristics of electric fast transient are carried out. It is pointed out that the probable high-frequency electromagnetic interference will probably influence the temperature measurement system.The paper enriches the study of the temperature measurement technology, confirms the problems and influence factors that may exist in application and provides a guideline and basis for solving the problems of temperature measurement applied in electrical equipment to ensure more stable work of the system.