230kV Dead Tank Circuit Breaker Governance: Eliminating PD via Precision Process & Smart Monitoring

Project Overview

After 10 years of operation, an LW56-230 dead tank circuit breaker at a 230kV substation was found to have partial discharge (PD) signals severely exceeding standards during ultrasonic testing (RMS 15mV, Peak 65mV—over 7 times the national standard). Disassembly confirmed that loose bolts had caused floating potential, and metal particles within the tank had triggered insulation aging. Our company urgently implemented the "Precision Governance Solution for Insulation Hazards," completing the repair within 72 hours through process purification, sealing reinforcement, and the installation of an online monitoring system. Post-governance, PD signals returned to safe thresholds (RMS≤1.8 mV, Peak≤4.5 mV). The equipment has operated safely for over 18 months, successfully averting the risk of a potential large-scale power grid outage.

Exceptional Design · Root Cause Eradication

Focusing on the trinity of "Impurity Control - Sealing Reinforcement - Intelligent Warning":

• Process Precision Control: High-precision CNC deburring combined with a three-stage purification process to completely remove metal particles; APG (Automatic Pressure Gelation) insulation components (strength ⬆30%) replaced aged parts.
• Sealing Upgrade: Fluororubber double-sealing + laser welding process ensures an SF6 leakage rate≤0.1% per year, preventing moisture intrusion.
• Intelligent Diagnosis & Control: Tank-embedded ultrasonic sensors combined with cloud algorithms capture real-time 50Hz/100Hz characteristic PD. Warning accuracy exceeds 98%, with localization precision reaching the centimeter level.

Empowering Infrastructure Development

This case led to the formation of the "Technical Guidelines for Governance of Latent Faults in EHV Dead Tank Circuit Breakers," which has been promoted to over 30 230kV substations nationwide, averting 47 similar hazards. Adhering to the philosophy of "Monitorable Warnings, Early Hazard Disposal," our company is driving the transformation of grid O&M from "periodic maintenance" to "condition-driven" strategies. This injects technical momentum into the high-reliability operation of new power systems and demonstrates our strength in safeguarding the full lifecycle of high-end domestic equipment.