| China’s economy continues to grow in recent years,and the scale of urbanization is more and more big,Industrial and residential demand for electricity continues to rise.In order to cope with the growing demand for electricity,the power industry has been increasing the construction of power infrastructure,the scale of urban distribution network structure is becoming larger and more complex.Therefore,it is of great significance for people’s daily social production activities to reduce the occurrence rate of distribution network accidents and improve the stability and reliability of power network work.As an important part of the distribution system,Temperature fault is common in high voltage switchgear,which is also one of the most harmful faults.Therefore,it is helpful to ensure the safe and stable operation of the whole distribution system to find faults of high voltage switchgear in time and take measures to eliminate them.At present,various temperature monitoring systems have been designed and applied in actual temperature detection,including infrared temperature measurement and fiber bragg grating temperature measurement,etc.However,due to more components,narrow space,complex mechanical structure in the high voltage switch cabinet,The existing temperature monitoring system has some disadvantages.In view of this situation,a temperature measuring system based on surface acoustic wave sensing technology is presented for internal equipment components of high voltage switchgear.This paper introduces several ways and basic principles of heat transfer,combined with the differential heat transfer equation of metal conductor,the convection heat transfer equation of metal conductor and air,the radiation heat transfer equation,the current conservation equation and the mechanical equation under thermal expansion,the multi-field coupling simulation software COMSOL was used to conduct the multi-field coupling simulation of the arc-extinguishing chamber of the vacuum circuit breaker and cable chamber in the switch cabinet.The temperature field distribution and the mechanical strain of cable chamber are obtained by modeling and calculating,it provides reference for the location selection of sensors in the system constructionIn the next step,the related principles of surface acoustic wave sensingtechnology are discussed in detail,the structure and classification of SAW temperature sensor are introduced,and the frequency response characteristics of single-terminal resonant temperature sensor are analyzed.The single-terminal resonant temperature sensor was used as SAW temperature sensor to construct the temperature monitoring system of high voltage switchgear.Based on the response characteristics of SAW temperature sensor,a read-write scheme framework including signal transmitting channel and signal receiving channel is designed,which is responsible for RF inquiry signal excitation and modulating echo signal reception,it mainly includes signal generation,signal frequency multiplication,signal mixing,power amplification and filtering,etc.The echo signal frequency is calculated by the master controller based on the fast Fourier transform,and the conversion of fequency to temperature data is realized.The communication terminal uses ZigBee wireless communication module to transmit temperature data to the PC terminal.Finally,a simulation test platform is built in combination with the cable room of the high voltage switchgear cabinet,the working performance of the designed signal read-write device is tested,and the corresponding relationship between frequency and temperature is found.In order to verify the accuracy of temperature measurement,it is compared with the digital sensor.The reliability of the passive wireless acoustic surface temperature monitoring system was tested under different humidity and current conditions,which accumulated experience for the practical application and improvement of the temperature monitoring system. |
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