Risk Assessment Method For Maintenance And Replacement Of High Voltage Cables Based On Statistical Model

The daily inspection and test of high-voltage cables can help discover and eliminate hidden dangers of cable failures.Timely replacement of aging cables can avoid the adverse effects of cable aging failures.Both are effective measures to reduce the failure rate.However,regular inspections and decommissioning replacement programs that ignore individual risk differences will lead to waste of manpower and resources.In order to ensure the reliable operation of cables and increase economic benefits,an optimization method is proposed for XLPE high-voltage cable maintenance and replacement strategies based on risk assessment.In order to meet the requirements of reliability and economy in maintenance decisionmaking,HV cable failure prediction and risk assessment methods are proposed.Firstly,historical failure data are collected,and the components of the cable system are divided into five parts: the main body,joint,terminal,earthing system,and conduit according to the inspection target.Based on those failures of cable components and maintenance experience information,a Bayesian inference and Weibull distribution failure rate/reliability evaluation method is proposed to establish cable failure mathematical model.Then,the risk of cable components is defined as the product of failure rate and importance according to the ISO55000 asset management standard,and the possibility and severity of failures of various components of the cable system are quantified,providing a basis for formulating maintenance and replacement strategies.In order to facilitate the daily inspection,an optimization method for maintenance scheduling of each component of HV cable is proposed,with the aim of reducing the cable system risk.Taking HV cables in Zhuhai as an example,the inspection periodicity of cable accessories with higher risk after optimization is significantly shorter than that of other components.In theory,the risk of cable failure can be reduced by 28.95% when the workload of operation and maintenance remains unchanged.In the case of perfect failure data,a time delay-based optimization method for the inspection cycle of HV cables is proposed to further improve economic benefits.The cable failure is regarded as a random process that obeys the statistical law,and the process of simulating the development of cable defects into failures.It provides a theoretical basis for scheduling inspection.After optimization,the inspection cycle of cable components is coordinated with the development of the defect to the failure time,and the defect is eliminated in time before the defect develops.Theoretically,the number of 103 failures can be reduced to 63,effectively reducing 24.33% of the maintenance economic expenditure.Aiming at the problem of decommissioning of aging HV cables,a method for the replacement of old cables based on risk assessment is proposed.Firstly,the ranges of cable failure rate and value of cable risk in different operating stages are calculated.Then replacement plan for aging components in the next five years is formulated.The case study shows that the two proposed replacement schemes can effectively reduce the cable aging failure rate and reduce the operation risk to the normal range,ensuring the economic and reliable operation of the cable.Overall,the risk assessment and maintenance scheduling methods proposed in this article take into account the reliability and economy of the cable,and provide a basis for maintenance strategies.Reliability analysis method combining Bayes inference and Weibull proportion hazard model solved the problem that effective reliability analysis results cannot be calculated with small samples.The risk based maintenance strategy can be conveniently implemented for the cable conduit,cable terminations,joints,main bodies and the earthing systems separately for each cable circuit.It can effectively reduce the failure rate and economic losses.In this way,maintenance can be scheduled through HV cable statistical data,rather than the original health evaluation method based on artificial scoring system.It can help the maintenance personnel to reasonably schedule the periodicity of inspection of different cable components,determine when to replace which aging cable components.And once a new cable failure is recorded,the maintenance and replacement strategy will be updated.