Cause Analysis of 35 kV Cable Terminal Joint Burning Failure

Based on the burnout failure of a 35 kV cable terminal joint during operation, the impact of improper model selection and processing during installation on the comprehensive performance of terminal blocks was analyzed. Through technical means including macroscopic inspection, dimensional measurements, chemical composition analysis, and scanning electron microscopy, the fault causes were investigated from multiple perspectives by integrating factors such as materials, structure, and construction techniques. Results showed that compared to the normal phase, the terminal block of the faulty phase was excessively thin in thickness and oversized in mounting hole diameter. When the terminal connectors were tightened with hot-dip galvanized high-strength bolts, deformation was easily caused, by which gaps were formed between the terminal blocks. Consequently, the contact resistance was increased and overheating was triggered; meanwhile, floating potentials were generated between the terminal blocks due to the existence of the gaps, which accelerated the electrical fault. These research results could provide a reference for the troubleshooting and resolution of similar cable terminal joint faults.