Research On Life Prediction Method Of Switching Equipment

Different kinds of switching equipment are widely used in power transmission,distribution and utilization.It is greatly important to the electrical system whether it can complete the designated switching task within the expected service lifetime.The end of electrical lifetime of switching equipment caused by contact wear is a common and predictable failure type.Based on this,numerous on-line monitoring and prognostics systems are emerging in recent years.However,related researches are still staying in the laboratory stage and difficult to be directly extended to practical application.Therefore,research on engineering implementation of electrical life prediction scheme of switching equipment is carried on in the paper.Firstly,the existing technical solutions to remain lifetime prediction are listed.And operating principle and fault type of switching equipment are also summarized.By comparing and analyzing several on-line monitoring systems based on different failure mechanisms,several key technologies of the electric lifetime monitoring schemes and the technical bottlenecks faced when it is applied to the project are clarified,which lays a theoretical foundation for the later research in this paper.Secondly,the solutions to the technical problems existing in two common electric lifetime prognostics schemes,one is based on accumulated wear and another is based on contact resistance,are proposed in the third chapter.Those include a method based on wavelet algorithm to determine the position of arc starting time and arc extinguishing time in breaking process,an off-line algorithm based on least square method and Ni curve to acquire the total allowable contact wear and calculation parameters,and a method based on improved Butterworth filter to calculate the contact resistance value.In addition,the feasibility and accuracy of the proposed theory are verified by experiments.Thirdly,we design and build an accelerated lifetime test platform suited for different type of switching equipment in order to further study the engineering implementation of the electric lifetime prediction scheme.The hardware architecture,equipment selection,software architecture,program flow and data acquisition system of the test platform are introduced in detail.In addition,the load setting and test procedures of the accelerated lifetime experiment are designed in combination with the device manual and relevant national standards.Ensure to obtain high-quality test data as soon as possible under the required condition.Finally,the distribution characteristics and functional relationship among contact resistance,arc current phase angle,arcing time and contact wear are analyzed based on the test data from the accelerated lifetime test.The probability distribution of the calculated value of contact resistance is studied and confirmed by Kolmogorov-Smirnov test.Based on the fact that calculated values of three-phase contact resistance are submitting to the kernel distribution,a method to reduce the calculation error of contact resistance is proposed too.Then the probability density and cumulative distribution function of the arcing current phase angle are studied,and the relationships among the arc current phase angle and the arcing time and the contact wear are also studied.The functional relationship of the contact wear and the arc current phase angle is found out,which lays a theoretical foundation for the engineering implementation of prediction scheme of switching equipment.