Troubleshooting HV Circuit Breaker Problems in the Field with Advanced Testing Techniques

The report includes numerous case studies conducted within our organization across different substations and circuit breaker types. Off-service test techniques such as timing analysis, dynamic resistance measurements (DRM), travel curve analysis, and coil current profile evaluation were applied. The test results revealed that installation errors and improper maintenance practices significantly affect circuit breaker performance. For instance, while misaligned mechanical components were found to impact operating times, travel curve, staticdynamic contact resistance and reduce overall reliability. In addition, maintenance-related issues such as the use of incorrect lubricants or improper replacement parts during previous service operations were observed to contribute to recurring faults in some circuit breakers. These findings were supported not only by quantitative data from diagnostic equipment but also by field experience and detailed post-test inspections.

Based on the off-service test data, corrective actions were limited only to circuit breakers that exhibited deviations in timing, contact resistance, travel curves, or coil current profiles.

This selective approach helped restore equipment to optimal operational parameters while avoiding unnecessary circuit breaker replacements and labor-intensive work. Consequently, maintenance resources were used more efficiently, and the strategy promoted condition-based maintenances rather than general maintenance.

Moreover, it was observed that the reference limits provided by some manufacturers were overly broad, which reduced sensitivity in detecting early-stage faults. Such wide thresholds may cause subtle but meaningful degradations in performance to go unnoticed, lowering the effectiveness of fault identification. Therefore, more precise thresholds based on accumulated field data are recommended to improve diagnostic accuracy and early warning capabilities.

The objective of this report is to promote the broader adoption of these field-proven testing methodologies, contribute to the evolution of maintenance strategies, and support the development of systematic approaches aimed at enhancing circuit breaker reliability.