High-Voltage Switchgear Trip Fault Analysis And Treatment Guide
In actual operation, switchgear tripping faults occur frequently due to various reasons. This guide aims to systematically explain the common causes, analysis methods, handling procedures, and maintenance points of high-voltage switchgear tripping.
High-Voltage Switchgear Trip Fault Analysis And Troubleshooting
When a high-voltage switchgear trips, never restore power blindly.
First, based on the action type (e.g., overcurrent, instantaneous trip, zero sequence, etc.) and indication of the relay protection device, make a preliminary judgment on the scope of the fault, and then conduct a systematic investigation.
Short-Circuit Faults
Fault Description: This is one of the most serious and common causes of tripping. It includes phase-to-phase short circuits and phase-to-ground short circuits, which generate huge short-circuit currents, causing the protection device to trip instantly.
Key Inspection Points:
Check the cabinet for obvious arc burns or melting marks.
Use an insulation resistance tester (megohmmeter or amperometry) to measure the insulation resistance of the main circuit and busbars to and from ground.
Check the contacts of the circuit breaker and disconnector for signs of welding.
Cable Faults
Fault Description: The outgoing cables connecting to the switchgear have experienced breakdown or short circuits due to insulation aging, mechanical damage, loose joints, or moisture.
Key Inspection Points:
Check cable terminations for discharge, creepage, or cracking.
Check cable joints for overheating, oxidation, or loosening.
Perform DC withstand voltage and leakage current tests on the cables to determine their insulation condition.
Voltage Transformer Faults
Fault Description: A short circuit between turns or between layers, or a single-phase ground fault, in the internal windings of a voltage transformer will cause the primary-side fuse to blow, and in severe cases, it will cause the protection system to trip.
Key Inspection Points:
Check the PT for bulging, oil leakage, or abnormal noises.
Measure the insulation resistance and DC resistance of its primary and secondary windings.
Check for short circuits in the secondary circuit.
Lightning Arrester Faults
Fault Description: After being subjected to lightning strike overvoltage or switching overvoltage, the surge arrester may experience valve plate breakdown or internal flashover, leading to continuous grounding or short circuit.
Key Inspection Points:
Observe the operation of the surge arrester counter and check for cracks or burns on its exterior.
Use a DC high-voltage generator to measure its leakage current and 1mA reference voltage to determine if its performance has deteriorated.
Overload And Current Surges
Fault Description: A sudden and significant increase in downstream load (such as the startup of high-power equipment) or a transient overvoltage in the system may cause the overcurrent protection to trip.
Key Troubleshooting Points:
Check the fault waveform data or the current values recorded by the protection device to confirm whether it is an overload.
Inspect the operation of the equipment on the load side and analyze whether any abnormal process operations have caused the inrush current.
Equipment Aging And Poor Contact
Fault Description: Wear and jamming of the mechanical mechanisms of circuit breakers and disconnectors, and oxidation and loosening of conductive circuit connections due to long-term operation, leading to increased contact resistance, causing localized overheating, and potentially resulting in insulation failure or arcing short circuits.
Key Inspection Points:
Use an infrared thermal imager to measure the temperature of all connection points inside the cabinet to identify any abnormal overheating points.
Check the mechanical characteristics of the circuit breaker (opening and closing time, speed, synchronicity) to ensure they are within acceptable limits.
Tighten all main and secondary circuit terminals.
Protective Device Failure
Fault Description: A fault in the protection relay or integrated protection device itself, or a loose, open, or short-circuited connection in its secondary circuits (such as current and voltage circuits), may cause the protection to misjudge and trip (false tripping), or fail to operate in the event of a real fault (failure to operate).
Key Points for Troubleshooting:
Check if the protection device has any abnormal alarm messages.
Verify that the protection device’s settings are correct and simulate its operating logic to ensure accuracy.
Check that the secondary circuit wiring of the current transformer (CT) and voltage transformer (PT) is secure and that there are no open circuits or grounding issues.
Environmental And Overvoltage Factors
Fault Description: A humid environment with condensation in the switchgear can significantly reduce insulation strength, leading to flashover. Intrusion of small animals (such as rats or snakes) can also cause short circuits. Furthermore, lightning strikes or overvoltages generated during operation can also break down weak points in the insulation.
Key Inspection Points:
Check the inside of the cabinet for condensation, water accumulation, and dirt.
Check if the moisture-proof and heating devices are functioning properly.
Check if the sealing of cable holes and other openings is intact.
Electrical Switchgear Maintenance
Prevention is better than cure. Regular, high-quality maintenance is fundamental to reducing switchgear tripping failures.
Regular Inspections: Conduct daily or weekly visual inspections, including instrument readings, indicator light status, and checks for abnormal sounds and odors.
Preventative Tests:
Insulation Resistance Test: Regularly measure the insulation resistance of the main and secondary circuits.
Contact Resistance Test: Measure the contact resistance of circuit breaker, disconnector contacts, and busbar connection points.
Mechanical Characteristic Test: Test the opening and closing time and speed of circuit breakers.
Relay Protection Verification: Regularly perform transmission tests and setting verification on protection devices.
Cleaning and Tightening: After power outages, thoroughly clean dust and dirt from inside the cabinet and tighten all electrical connection bolts.
Environmental Control: Ensure good ventilation in the distribution room, maintain temperature and humidity within standard ranges, promptly repair and seal any obstructions, and prevent small animals from entering.
FAQ
What Are The Most Common Causes Of High-Voltage Switchgear Failures?
The most common causes include short circuits due to insulation deterioration (caused by aging, moisture, and dirt), cable and joint failures, secondary circuit problems of protection devices, and poor contact due to mechanical wear of equipment or oxidation of connection points.
When Should I Seek Professional Assistance Immediately?
When the following situations occur, do not handle them on your own and immediately contact professional technicians:
There is a noticeable explosion, thick smoke, or continuous electric arc inside the cabinet.
The protective device issues serious alarms such as “control circuit disconnection” and “abnormal gas pressure”.
Repeated attempts at power transmission have failed, and the fault point cannot be clearly identified.
Issues related to SF6 circuit breaker gas pressure or vacuum circuit breaker vacuum degree that require professional instrument testing.
What Are The Main Aspects Of Routine Maintenance For Electrical Switchgear?
Daily maintenance mainly includes:
Observe whether there are any abnormalities in the instruments, signals, and appearance.
Listen: Listen carefully for any abnormal noises such as discharge or vibration inside the cabinet.
Smell: Smell for the smell of burnt insulation.
Note: Record running parameters and abnormal situations.
Regular execution: Conduct power outage cleaning, fastening, functional testing, and preventive testing according to the plan.
What Support Can Byyou Provide For Electrical Cabinets?
As a professional electrical solutions provider, Byyou offers the following services:
Technical Support: Providing fault diagnosis, maintenance guidance, and technical consultation for switchgear.
Spare Parts: Supplying high-quality original or certified spare parts to ensure equipment compatibility and reliability.
Maintenance Services: Providing professional regular maintenance, preventative testing, and equipment upgrade services.
Training: Providing professional training for customers’ technical personnel in operation, maintenance, and troubleshooting.
Conclusion
By understanding the underlying causes of various faults, mastering correct troubleshooting methods, and implementing regular maintenance plans, the operational reliability of switchgear can be greatly improved, unexpected downtime can be minimized, and the safe and stable operation of the power system can be guaranteed.
PS: When facing complex or high-risk faults, it is essential to seek professional support to ensure that the problem is resolved safely and thoroughly.
