Numerical Simulation Of The Stress Distribution And Failure Mechanism Analysis On Rod Post Porcelain Insulator

With the increase of service time, power grid accidents caused by the rodporcelain insulator defects increase gradually in the level of500kV and below in ourcountry. It not only causes great economic losses but also endanger the personalsafety. With the development of EHV and UHV engineering construction, theelectrical properties, seismic performance of rod post porcelain insulator, especiallymechanical properties draw more researchers’ attention.The mechanical performance evaluation of post porcelain insulator is commonlymeasured by bending strength or bending failure load. Owing to the risk, high cost ofthe whole column bending failure test, in this paper, numerical simulation method isused to calculate and analyze the stress and its distribution law of rod post porcelaininsulator, and to provide certain theoretical reference for assessment of the postbearing capacity. This paper involves the calculation based on the linear elasticmechanics theory, focus on discussing the effect of defects (such as crack) on thestress field and distribution. The results were showed as following:1Defects may have a significant impact on porcelain stress especially themaximum stress distribution, which is related to the defect location, size and shape.Thus the porcelain strength will be also affected by the abovementioned defectfeatures. The defects in the tensile stress area have a greatest impact on the strengthdegradation. The degree of the strength degradation mainly depends on the nominaltensile stress value at the defect. With the same location, the size and shape change ofthe defects will cause important influence on the strength of the porcelain.2Based on the finite element model of the post porcelain insulator, thesimulation calculation results for whole column and add extension rod post insulatorunder bending in the same condition were obtained. It showed that in most cases themaximum principal stress of the latter is greater than the former, so the porcelainstrength measured by add extension rod test is lower than the whole column test.3The calculation results of the stress intensity factor of crack front under postbearing process with axial offset showed that the destruction of the porcelain was theresult of the interaction of crack typeⅠandⅡ. When the axial deviation angle is small,crack typeⅠis priority. When the deviation angle increases to a certain value, thevalue of KIIbegins to increase. With the load increasing continually, KIand KIIvalue of the crack front reaches the crack propagation critical condition, porcelain willhappen instantly brittle fracture.