Maintenance Strategy Of Transmission Cable With Outer Sheath Insulation Defect Considering Its Operation Risk

The outer sheath of power cable has the function of protection and insulation,its integrity is the guarantee of safe operation of power cable.Guangzhou is warm and humid,where high level of groundwater exists.The environmental factors,such as groundwater,termite and microorganism,have a negative effect on the performance of outer sheath,there is a general phenomenon that outer sheath with low insulation resistance.Outer sheath with low insulation resistance will not directly affect operation of power cable,but defect location and maintenance of outer sheath need a lot of manpower and material resources,operation department generally don't solve the problem that outer sheath with low insulation.However,the low insulation resistance of the outer sheath has become a hidden danger in the operation.In order to improve safety and reliability of cable operation,it is necessary to put forward reasonable and proper maintenance strategy for different situation of outer sheath insulation.Based on outer sheath insulation resistance measurements of 110 k V and 220 kV cable in Guangzhou,main reasons for reduction of outer sheath insulation resistance and the influence on cable operation are analyzed.The method of failure risk analysis for power equipment based on failure mode is used to analyze the risk of high voltage cable with outer sheath defects continuing operation,which establish a single chain model including one main reason that leads to insulation resistance reduction of outer sheath.This paper puts forward maintenance decision for different cable defects based on the risk analysis of cable with low outer sheath insulation.The risk analysis of low insulation outer sheath can explore the failure evolution process from the beginning.It is helpful to construct comprehensive and reasonable risk assessment system for transmission cables,to provide support for improving maintenance decision and operation suggestion of transmission lines,and to achieve the purpose of reasonable control of economic losses caused by cable failure.