Research And Design Of High Voltage Line Interphase Short Circuit Fault Detection Device

At present,automatic reclosing is commonly used in high voltage transmission lines in our country to solve the problem of transmission line fault.Reclosing can improve the reliability of power supply to some extent,but it can not judge whether the short circuit fault of the line is eliminated before the reclosing operation.Therefore,it is impossible to determine whether it is instantaneous short circuit or permanent short circuit.Failure,which may cause reclosure to coincide with permanent short-circuit fault.In order to solve this problem,a device with simple structure and easy to carry is designed,which can quickly and accurately identify the nature of interphase short circuit fault,so as to ensure the efficient operation of reclosing and the safety of the maintenance personnel of the power system.A device based on high frequency injection method to identify the characteristics of short circuit fault of high voltage transmission line is designed and studied.The device consists of voltage transformer,charging module,supercapacitor bank,high frequency inverter module,intelligent control module and result output module.The voltage transformer completes the function of the high voltage line,then uses the charging module to charge the supercapacitor to the target voltage.When the fault detection is needed,the supercapacitor group is used to discharge the post stage circuit.At the same time,the high frequency inverter module is started to generate high frequency voltage signal to high frequency injection to the high voltage line.Finally,the high frequency voltage is injected to the high voltage line.Finally,the high frequency voltage signal is injected to the high voltage line.Finally,the high frequency voltage signal is injected to the high voltage line.Finally,the high frequency voltage signal is injected to the high voltage line.The discharge time of the supercapacitor group is timed with the STM32 single chip microcomputer,and the transmission line is identified as a transient short circuit fault or a permanent short circuit fault according to the discharge time.Under the condition of permanent short circuit fault,the discharge current of the supercapacitor is far greater than the discharge current under the instantaneous short circuit fault.Therefore,the over current protection mechanism can be set up for the post stage inverter module.At last,the transient fault and the permanent short circuit fault can be identified by judging whether the overcurrent protection is started.The simulation model of the system is built with Simulink.The simulation results verify the feasibility of the control.Finally,the software program is written and the hardware circuit is built according to the design requirements.Through the comprehensive hardware debugging,the STM32 SCM is used as the control core,and the supercapacitor bank is discharged to the target voltage by using the STM32 single chip microcomputer.The time used is timed,and the STM32 MCU is used to judge whether the circuit has overcurrent protection.At last,through the comparison of the discharge time and the over current protection of the circuit,the recognition power of the instantaneous short circuit fault and the permanent short circuit fault of the high voltage transmission line is realized.The test results show that the design scheme is correct and feasible,and the circuit can effectively judge the fault nature,and the comprehensive performance index meets the design requirements.