Root Cause of Relay Insulation Failure and Renovation Measures in HVDC Projects

During the operation and maintenance of HVDC projects, relay insulation failure caused several unexpected AC filter trip events, which affected the safe operation of HVDC projects. The failure reason of insulation is analyzed in this paper, there is oil like conductive liquid on the plastic surface of failed relay, this paper researches the structure of the relay, analyses the components of the liquid, and assumes the source of the liquid is the auxiliary additive in plastic based on the components comparison of liquid and plastic. The experiment based on time-temperature equivalence principle verifies the assumption, revealing the reason of the relay insulation failure. At last, the paper proposes corresponding short term and long term renovation measures, and successfully solves the relay insulation failure problem.