| In the field of GIS disconnecting switch contact temperature monitoring, wireless temperature measurement method has problem of battery maintenance, and there exists hidden danger of battery safety. Infrared temperature monitoring technology needs large transformation of GIS cavity, parts of the regions cannot be directly monitored because of optical path resistance. For the FBG temperature monitoring technology, it is difficult to layout the optical fiber without flashover risk. Compared with the traditional temperature sensors, surface acoustic wave (SAW) temperature sensor has a better insulation and is electromagnetically immune. Besides, depending on wireless and passive sensing technology, SAW temperature sensor can work without power supply. Thus, SAW technology has a broad application prospect in the GIS Contact Temperature Monitoring field.In this paper, firstly the transmission and measuring principle of SAW is analyzed. The manufacturing method of SAW chips is researched and SAW chip of YX- Quartz is chose for designing the temperature sensor. According to the influence of manufacturing processing on the SAW device performance, selection method and temperature stability of SAW chips are researched. According to the principle of SAW temperature sensors, the influences of environmental factors on SAW temperature sensors are studied, including vibration and physical structure. The results showed that the main frequency band of vibration inside GIS is below the SAW signal detection frequency band, which can not affect the detection. According to the analysis of SAW signal attenuation in different GIS structure, a reader antenna should be embedded in the GIS cavity to introduce signal into GIS.For better monitoring on GIS contact operation temperature, an annular contact temperature sensor based on SAW technology is developed with high gain and low loss. The sensor is installed on the bus close to the contact to obtain the GIS contact parts of the temperature indirect. In order to ensure the communication, a high performance of the reader antenna is designed with the advantages of high gain and broad band, which can also be used as PD antenna when necessary. To generate the inquiry signal, and to analysis the echo signal, the monitoring system software are designed based on Lab VIEW software. Because of the complex structure of GIS, in order to ensure the accurate measurement of SAW temperature monitoring system, the propagation characteristics of electromagnetic wave signal in GIS is researched. Anti electromagnetic interference performance of the SAW sensor is proved by theoretical analysis and test.To verify the working performances of the SAW sensor, static performances tests have been performed in the laboratory. Results of the experiments showed that within the range of 0～100 C, the nonlinear error of SAW temperature sensor is 0.98% and the sensitivity is 7.072kHz/C. Tests also showed that SAW temperature sensor precision is 2.1%, the hysteresis error is 2.49% and the highest response speed is 1.7℃/s.To test the performance of temperature monitoring system in the actual natural environment, the temperature test was conducted inside GIS. Experimental result shows that the SAW temperature sensor works properly in electromagnetic environment. With the help of SAW temperature measurement system, the GIS contact temperature can be obtained. |
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