Analysis Of Switching Characteristics Of High Voltage Parallel Capacitor And Design Of Condition Monitoring Sensor

High voltage parallel capacitor plays an important role in compensating reactive power,improving power factor and ensuring power quality.In order to meet the requirements of economic operation of power grid,parallel capacitor banks often need frequent switching.The severe transient phenomenon in switching process will pose a great threat to power grid security.It is very important to ensure the safe operation of capacitors.Therefore,it is of great practical significance to analyze the switching characteristics of parallel capacitor and monitor its operation state.Based on the analysis of the working principle of parallel capacitor switching circuit,the transient process of switching is simulated to obtain the characteristics of electrical parameters,and a series of state sensing sensors are developed to withstand the extreme conditions of capacitor switching.Firstly,the electrical parameter equation is theoretically derived through the switching working circuit of parallel capacitor.The transient characteristics such as switching inrush current and harmonics are analyzed,and the reburning overvoltage caused by arc reburning phenomenon when the capacitor is out of operation is analyzed,and the harm of switching limit parameters to the equipment is analyzed.Secondly,in order to study the attenuation change of current value at the moment of closing,the overcurrent and oscillation of three-phase asynchronous closing and overvoltage during normal and abnormal opening,the simulation model of capacitor switching characteristics is built in PSCAD/EMTDC.Finally,the technical indices of sensor which can meet the requirements of capacitor monitoring field are determined.Finally,according to the field requirements,the structure and working circuit of capacitor condition monitoring sensor are designed.Taking the bus current,capacitor voltage and unit current as state variables,the key module circuits and functional programs such as high-voltage energy acquisition,data transmission and measurement are designed to realize the development of low-power high-voltage energy acquisition,wireless networking and micro intelligent sensors.After passing some relevant tests like electromagnetic interference,measurement accuracy and Zig Bee wireless networking,the developed sensor is installed and tested at the substation site.Finally,the performance of the sensor is verified to meet the design requirements.Based on wireless network,the micro monitoring sensor of capacitor has made great progress in structural miniaturization,energy acquisition in high-voltage environment,anti-interference and insulation design.It provides some important technical means for the promotion and implementation of equipment’s condition maintenance and ensuring the safe and economic operation of power grid.