Research On On-line Monitoring Of 126kV Permanent Magnet Vacuum Circuit Breaker

As an important member of high voltage electrical equipment,the high voltage circuit breaker plays the role of control and protection in the power system.Once the circuit breaker breakdown,it is extremely likely to bring about power grid accidents,affecting people's production and life.On-line monitoring of circuit breaker can detect potential problems and solve them timely,reducing frequencies of power outages and overhauls as many as possible.Thus,on-line monitoring for circuit breaker is of great practical significance for improving power system's safety and reliability.Firstly,the research status of on-line monitoring technology of the permanent magnet vacuum circuit breaker(PMVCB)is introduced.In order to obtain moving contact's displacement of the circuit breaker,several measurement methods along with their respective advantages and disadvantages are presented.The chosen approach is using high-precision displacement sensor.This thesis also introduces several methods to distinguish the very moment when the circuit breaker switched on or off,and the chosen approach is distinguishing the moment when the force,acting on the linkage which is connected with the moving contact,has a sudden change.And the rationality of this approach is discussed.Secondly,the hardware circuit,which is composed of control,driving,data acquisition and communication parts,of on-line monitoring system for 126kV PMVCB is designed.And the working principle of each part is also presented.The related circuits used for sampling the signals,which includes the operating coil current,energy storage capacitor voltage,grid voltage and grid current,are elaborated in detail.The communication mode between DSP and computer is also introduced.This thesis expounds software design's principle of the control system,both the flow of driving control and data sampling of 126kV PMVCB are introduced in detail.Based on MFC,the interface of the host computer is designed,which can not only send out commands to the DSP,but also display sampling data.The implementation principles of these functions are described in detail.Finally,the on-line monitoring device of 126kV monostable PMVCB was tested.The experimental results prove that the on-line monitoring system is stable and the measurement accuracy can reach the expected requirements.