Research On State Evaluation Method Of Power Equipment Based On Reliability Theory

With the rapid development of the power system,building a strong smart grid and global energy Internet is an established development of its power industry,and the economic and social requirements for power quality are constantly increasing.As an important part of power system,the state evaluation of power equipment is one of the important methods to master the insulation state of power equipment,which can comprehensively reflect the deterioration of its insulation system.At the same time,effective and reliable condition assessment can provide preconditions for the formulation of maintenance strategy and prevent the occurrence of major accidents.Therefore,the state evaluation of power equipment is related to the safe,reliable,stable and economic operation of the whole power system.In this paper,the state evaluation of power equipment is mainly carried out from two aspects:ZnO oxide arrester and XLPE cable.Firstly,the data of power failure test and live detection test of zinc oxide arrester in Guangzhou are analyzed,and the influence of ambient temperature,humidity and operation life of arrester on site data such as reference voltage and leakage current is studied.Finally,a correction method of field test data of zinc oxide arrester is proposed to reduce the interference of environmental temperature and humidity factors on the measurement results,so as to achieve a more accurate state evaluation results of zinc oxide arrester according to the indicators of field test data.Aiming at the situation that the lightning arrester is subjected to random stress such as lightning during operation,a ZnO lightning arrester failure probability estimation model based on reliability theory is established in this paper.The model can make full use of the leakage current,the probability distribution of lightning current amplitude,and the volt ampere characteristics of nonlinear resistance of arrester.The distribution of thermal power of lightning arrester under the action of lightning is obtained,and then the probability of lightning failure is solved.The study on the condition evaluation of XLPE cables is mainly from the perspective of cable failure probability estimation.The system-level XLPE cable condition assessment system is established.Based on the theory of stress intensity interference in the field of mechanical reliability,a model for estimating the probability of partial discharge and overheating failure of XLPE cable is established.Aiming at the problem of partial discharge failure of XLPE cables,by analyzing the partial discharge data of field failure XLPE cables,the failure probability estimation method of partial discharge faults based on the stress-strength interference model is studied,which can characterize the severity of the partial discharge defects of the cable.By exploring the quantitative relationship between the local discharge value and the length of the electrical tree in the cable insulation,an estimation model of partial discharge failure probability of XLPE cable based on the.stress intensity interference model considering the temperature effect is proposed.And the probability of fault caused by partial discharge defect of XLPE cable can be solved by integral method,which improves the accuracy of state evaluation of XLPE cable.