Mechanical Condition Evaluation Method Study Of Circuit Breaker Based On The Analysis Of Coil Current Signal And Vibration Signal

The circuit breaker is the most important electrical equipment in high voltage switchgear,it can quickly cut off the fault part to guarantee the normal operation of the non-fault part when a fault occurs in the system,so its reliability is related to the safe and stable operation of power system and it is very important to monitor and evaluate its running state.The research shows that the electromagnet coil current signal(i.e.coil current)and vibration signal of circuit breaker contain a quantity of equipment status information,so extracting characteristic quantities from coil current and vibration signal is a reliable method to realize the condition evaluation of circuit breaker.This paper used signal sensors,data acquisition cards,and other hardware and LabVIEW software to build up circuit breaker data acquisition system,the designed system realized the functions of collecting,storing and analyzing the multi current/voltage signals and vibration signals of the circuit breaker.Under the condition of several circuit breakers(such as vacuum circuit breakers,SF6 breakers,GIS breakers etc.),a series of fault simulation tests were carried out;take vacuum circuit breaker test as an example,5 fault states simulated which were electromagnet clamping,electromagnet loosening,high operating voltage,low operating voltage and buffer clamping,then circuit breakers 3 phase fracture signals,vibration signals at 8 positions and the coil current signal were collected under the condition of 6 circuit breakers states which including normal state.The coil current and vibration signal were analyzed in detail from signal preprocessing,signal processing,feature extraction and feature weight analysis;wavelet multi-scale decomposition method and morphological method were used to reduce the noise in signal;based on the analysis of vibration signal in time domain and frequency domain,paper proposed to use the short-time energy method in the analysis of vibration signal,then extracted the vibration event start time,vibration event extreme point occurrence time,wavelet packet layered energy value as the vibration signal characteristic parameters;for the coil current signal,take the time and amplitude at specific point which can represent its characteristics as the characteristic parameters;then the Relief algorithm is applied to calculate the characteristic parameters weight,and according to the results,the characteristic parameters can be optimized.On the basis of the above analysis,by using fuzzy clustering algorithm,support vector machine algorithm and the extracted characteristic parameters from coil current and vibration signal,realized the condition evaluation of circuit breaker under the test simulation;the results show that the extracted coil current characteristic parameters can accurately realize the circuit breaker state evaluation;the extracted vibration signal characteristic parameters(the vibration event start time and the vibration event extreme point occurrence time)can also realize circuit breaker state evaluation;however,due to the poor stability of the frequency domain characteristics of the collected vibration signals in the same state,the use of the wavelet packet layered energy value as the characteristic parameters of the vibration signal for the circuit breaker state evaluation is not very accurate.In the actual operation of the circuit breaker,the fault types may be complex and varied,only use one signal to achieve circuit breaker state assessment may exist judgment error or judgment failure,paper proposed a new condition evaluation method based on different signals characteristic parameters fusion,the results show that the method can more accurately realize the state assessment of circuit breakers under complex faults.