Research On Online Monitoring Of Mechanical Characteristics Of 12kV Ring Main Unit

The 12 kV ring main unit is widely used in power distribution systems,and its mechanical characteristics reflect the opening and closing performance of the ring main unit.The existing test methods for the mechanical characteristics are mainly based on the realization of simple and accurate displacement sensors.Due to the compact internal structure and narrow space of the ring main unit,it is difficult to achieve the online monitoring of mechanical characteristics in the existing method.The acceleration sensor is small in size and easy to be fixed,and the stroke curve can be obtained through the integration method,which can solve the defect of the displacement sensor in online monitoring of the mechanical characteristics.This article will focus on the application of acceleration sensors in the online monitoring of the mechanical characteristics of the ring main unit.Firstly,the relevant standards of the ring main unit and its online monitoring of mechanical characteristics are studied,and the testing requirements for the online monitoring of mechanical characteristics are determined.Aiming at the difficulty of achieving online monitoring of traditional displacement sensor detection schemes,the acceleration sensor is selected as the online monitoring sensor scheme,and the acceleration sensor application problems are analyzed.Secondly,with the embedded system STM32 as the core,the software program and the hardware circuit are designed to achieve the online monitoring and testing platform for the mechanical characteristics of ring main unit.Control the ring main unit circuit breaker to conduct the test,and simultaneously collect the displacement signal,acceleration signal,break signal and the current of the opening and closing coil.The collected data is sent to the host computer for data analysis and processing.According to different acceleration sensors,experiments under different conditions are conducted to further select and optimize the sensors.Then,it is studied that using the acceleration signal to determine the moment when the ring main unit contacts are separated and closed.Analyze the characteristics of the acceleration during the opening and closing process.Combining with the sudden change of acceleration at the moment of just opening and closing,the mo ment of sudden change of acceleration can be determined by the maximum value of the wavelet transform modulus.In this way,the moment of opening or closing of the contact in the process of opening and closing of ring main unit is determined.Finally,the method of acquiring the moving contact stroke of the ring main unit based on the contact acceleration integration is studied.Kalman filter is used to filter the acceleration signal of opening and closing.Analyze and verify the practicability of time-domain and frequency-domain integration in circuit breaker opening(closing)acceleration integration,and finally select the time-domain integration algorithm to integrate the filtered acceleration signal to obtain the travel-time curve of the contact.In the opening process,the inherent opening time,overrun and average opening speed are calculated;in the closing process,the closing time,opening distance and average closing speed are calculated.