What are the common faults of 35kV high-voltage circuit breakers?

High-Voltage Circuit Breakers: Common Faults and Solutions for 35kV Systems

High-voltage circuit breakers are critical electrical equipment in power substations. A thorough understanding of their fault patterns and root causes enables targeted troubleshooting, rapid power restoration, and effective reduction of losses caused by outages and equipment damage.

I. Common Operational Faults of 35kV High-Voltage Circuit Breakers

1. Failure to Store Energy (Charging Failure)

Energy storage is the foundation for circuit breaker operation. If the breaker cannot store sufficient kinetic energy, it may fail to perform normal opening or closing operations. A common cause is malfunctioning limit switches, which can cause the energy storage motor to run continuously. Under normal conditions, the motor stops automatically once the mechanical travel is complete. If the limit switch fails to detect the end position, the motor continues running, leading to energy waste and potential damage to the motor or storage mechanism.

2. Mechanical Failures Preventing Closing

Mechanical faults can prevent both opening and closing operations, resulting in local manual tripping failure. When remote control commands are used, a fault in the control circuit or relay protection system can also prevent successful closing. Open circuits in the trip coil or trip control circuit can lead to failure to close. Stable voltage supply is essential during operation; when supply voltage drops, the coil resistance increases, reducing tripping capability. Mechanical sticking or jamming during the trip process can also affect the closing operation, severely compromising the breaker’s functionality.

3. Closing Coil Burnout

Faults in spring-operated mechanisms can reduce energy storage efficiency. If the spring fails, the energy storage circuit cannot fully charge, causing the motor to remain in continuous operation, potentially leading to motor coil overheating and burnout. A common cause of closing coil burnout is improper positioning of the limit switch—installed too low—causing the motor to start before the spring is fully charged. This results in excessive current draw and elevated coil temperature. Even after the switch contacts change state and cut off power, the spring may lack sufficient energy to complete the trip operation. Prolonged motor operation under these conditions can also damage the limit switch. Such faults prevent normal opening/closing operations and increase the risk of internal component damage.

II. Solutions for 35kV High-Voltage Circuit Breaker Faults

1. Monitor Energy Storage Motor Operation

Given the critical role of the storage motor, maintenance personnel must regularly inspect its operation. Improper limit switch positioning can prevent the motor from stopping correctly. The switch must be installed to ensure timely motor shutdown once full energy storage is achieved, providing reliable and orderly kinetic energy supply.

2. Inspect Trip Coils Regularly

Maintenance staff should conduct timely and effective inspections of trip coils to identify potential faults and hidden risks, preventing incident escalation. Key inspection points include:

• Checking for open circuits in the trip coil (replace if damaged)

• Verifying continuity in the trip control circuit

• Inspecting the trip plunger for deformation

• Ensuring the breaker can operate freely

An open circuit in the control loop prevents sufficient current flow, impairing breaker performance. Regular checks ensure safe and reliable operation.

3. Strengthen Circuit Breaker Maintenance

Enhance training for maintenance personnel on technical knowledge and fault analysis. Organize case studies to identify gaps, improve response capabilities, and build expertise in accident prevention and emergency handling. Learn from past incidents to avoid recurring human errors.

Strictly manage high-voltage switchgear. After a fault trip, never force-energize without identifying the root cause, as this risks personnel safety and may expand the incident. Isolate switchgear that tripped under abnormal conditions, conduct thorough inspections, tests, and adjustments, and only return to service after confirming complete safety.

Standardize substation operating procedures, detailing every step to ensure operational uniqueness, enhancing both personnel safety and equipment integrity.

4. Resolve Circuit Breaker Failure to Close (Refusal to Close)

To address refusal to close:

• Insert a normally closed (NC) auxiliary contact of the high-voltage circuit breaker into the LD signal lamp circuit. After closing, no current flows through the TBJ voltage coil, eliminating holding voltage. After tripping, this setup both monitors the closing circuit integrity and indicates the open status.

• Alternatively, relocate the LD wiring so that after TBJ operates, the LD disconnects from the voltage coil. However, this modification may be complex in some breaker mechanisms.

• If no spare NC contact is available, connect an auxiliary resistor (R) in parallel with the TBJ voltage coil to limit its voltage to ≤30% of rated voltage, preventing unintended operation.

5. Adjust Limit Switch Position

Incorrect limit switch positioning (too high or too low) can cause faults. If energy storage is incomplete, excessive current and voltage may flow, leading to circuit failures. Maintenance personnel must promptly adjust the switch position to prevent incident escalation. Proper adjustment ensures the motor stops precisely when charging is complete. During switching operations, rely on the energy storage indicator light to confirm readiness. Only when free opening/closing is verified can the breaker be considered in good condition. Correct limit switch positioning is fundamental to reliable 35kV breaker operation and accident prevention.

Conclusion

Electricity is a vital energy source for national economic development. Ensuring high-quality power supply and grid stability is paramount. High-voltage circuit breakers are essential for protecting and controlling the safe operation of power systems. Their reliable performance is crucial to overall grid stability. Therefore, substation maintenance personnel must fully understand the operational status, fault patterns, and root causes of high-voltage circuit breakers, and be capable of implementing effective corrective actions. Timely fault resolution ensures grid safety and delivers high-quality, efficient power to users.