Fault Analysis and Corrosion at the Lead Seal of High-Voltage Cable Joint

The joint of high-voltage cables is a vulnerable component in cable systems, and the lead seal is an important part that connects the aluminum sheath and cable accessories. Firstly, three typical cases of 110 kV high-voltage cable joint copper tailpipe breakdown accidents caused by lead seal failure in recent years were analyzed. The results showed that the failure of a single lead seal does not change the potential and electric field intensity inside the copper tailpipe. Instead, it mainly affects the circulating current path in the metal sheath, ultimately leading to breakdown accidents due to Joule heating effects. Electrochemical workstation experiments demonstrated that the aluminum sheath in the lead seal section is most susceptible to oxidation dissolution in electrochemical reactions. Finally, combining the accident analysis with the test results from the electrochemical workstation, the electrochemical corrosion of the lead seal section is systematically introduced. The use of hydrogen gas as a characteristic gas for characterizing the corrosion status of the lead seal section is proposed, and its effectiveness is verified in decommissioned and in-service cables.