What maintenance work should be done for outdoor high-voltage vacuum circuit breakers?

Outdoor high-voltage vacuum circuit breakers are critical equipment in power systems, and their reliability is directly related to the safe and stable operation of the power grid. Their maintenance must be systematic and standardized.

The following maintenance tasks for outdoor high-voltage vacuum circuit breakers can be divided into three levels: daily inspections, regular maintenance (pre-testing), and post-fault inspections.

Daily Inspection (Visual or Simple Inspection)

This is the most basic and crucial maintenance, designed to promptly identify potential problems.

Appearance Inspection:

Integrity: Inspect the housing for damage, cracks, rust, or deformation.

Sealing: Observe the sealing ring for signs of aging or cracking, and the joints between the housing and the housing for signs of oil, water, or dust leakage. Proper sealing is crucial for preventing moisture and condensation.

Signage: Inspect the signage for clarity and integrity.

Electrical Connections:

Connectors: Inspect the primary terminals for signs of overheating, melting, or oxidation discoloration (this can be checked using color change, temperature-indicating wax strips, or an infrared thermometer).

Insulators: Check the surface of the porcelain or composite insulator for cleanliness and for flashovers, cracks, damage, or severe contamination.

Mechanical Units:

Open/Closed Position Indicator: Check for correct indications and consistency with the backend monitoring signal.

Charged Energy Indicator: For spring-operated mechanisms, check for normal charged energy status.

External Environment:

Debris Removal: Remove any debris, such as bird nests and vines, from the circuit breaker body and mechanism box.

Foundation Inspection: Check the installation foundation for any sagging or tilting.

 

Regular Maintenance and Preventive Testing (Power Outage Inspection)

This is core maintenance work and must be performed by professionals during a power outage. It is usually conducted in conjunction with the power department's "Preventive Testing Procedures."

Insulation Performance Testing:

Insulation Resistance Test: A megohmmeter is used to measure the insulation resistance between the terminals (in the open state) and to ground (in the closed state) to determine if the insulation has been exposed to moisture or deteriorated.

Power Frequency Withstand Voltage Test: This is a key test to verify the strength of the main insulation. According to regulations, a power frequency high voltage is applied to the terminals and to ground for a specified time to ensure that it can withstand the overvoltages encountered during operation.

Main Circuit Resistance Measurement (Contact Resistance):

Use a circuit resistance tester (micro-ohmmeter) to measure the DC resistance of the main circuit (including the vacuum interrupter and conductive connections) of the circuit breaker in the closed state.

Purpose: To check for wear and aging of the moving and static contacts, and to ensure proper internal connections. The resistance value should not exceed 20% of the factory or initial commissioning value.

Mechanical Characteristics Test:

Use a high-voltage switch mechanical characteristics tester for measurement, which is the most important means of assessing the health of the mechanism.

Measured Parameters:

Opening and Closing Time: Checks compliance with technical specifications.

Opening and Closing Speed: Excessively slow speeds may result in prolonged arcing or closing bounce, damaging the contacts.

Opening and Closing Synchronicity: Checks the synchronicity of the opening and closing of the three-phase contacts.

Bounce Time and Count: Contact bounce during closing should be minimized.

Coil Current Waveform: Analyzing the current waveform of the operating coil can determine if there are any problems with the electromagnet or locking mechanism.

Operating Mechanism Inspection and Maintenance:

Spring Operating Mechanism:

Check the closing spring for integrity and rust.

Inspect the energy storage motor, gears, clutch, latch, and other components for wear and sticking, and apply an appropriate amount of special grease.

Check the fatigue of the opening and closing springs.

Solenoid Operating Mechanism: Check the DC resistance and insulation of the opening and closing coils, and check that the core operates smoothly without sticking.

Linkages: Check all linkages and pins for wear and deformation, and ensure that fasteners are not loose.

Secondary Circuit and Auxiliary Component Inspection:

Opening and closing coils: Check their operating voltage; it should operate reliably within 65% to 120% of the rated voltage.

Auxiliary Switch (Microswitch): Check for good contact and correct, reliable switching positions.

Energy Storage Switch and Counter: Check for proper function.

Secondary Wiring: Check that the terminal blocks are securely connected and that the wire numbers are clearly marked.

Testing the Vacuum Interrupter Chamber's Vacuum Level (Critical Item):

Vacuum level is the lifeblood of a vacuum circuit breaker. Although the vacuum level will slowly decrease during operation, once it falls below a critical value, interruption failure will occur.

Testing Methods:

Power Frequency Withstand Voltage Test: The most commonly used and reliable method. In the open state, a specified power frequency voltage (e.g., 42kV) is applied to the interrupter. If it withstands a flashover for one minute, the vacuum level is considered acceptable.

Magnetic Discharge Test: Quantitative measurement using a dedicated vacuum tester is more accurate but more complex.

Checking Anti-Condensation Measures:

Check that the heaters and temperature and humidity controllers in the mechanism and control boxes are functioning properly, and ensure the box is dry.

The vacuum level will slowly decrease during operation,once it falls below a critical value,interruption failure will occur.

 

Special Inspections After Fault Tripping

After a circuit breaker successfully interrupts a short-circuit fault, even if routine test data is normal, the following inspections should be performed as appropriate:

Panoramic Inspection: Focus on inspecting the exterior for any abnormalities, such as smoke marks on the nozzle.

Transfer Current Interruption: For circuit breakers that frequently interrupt load currents or capacitor banks, the vacuum level check and loop resistance measurement intervals should be appropriately shortened.

Recording and Analysis: Record the fault current and tripping times as a basis for assessing the circuit breaker's lifespan.

Recommended Maintenance Cycle
Daily Inspection: Weekly or monthly, depending on the criticality of the equipment.

Periodic Maintenance: The first inspection should be performed one year after the equipment is put into operation. Thereafter, the inspection should be performed every three to six years, depending on the equipment's operating conditions and criticality. In harsh environments or where equipment is frequently operated, the inspection interval should be shortened.

Post-Fault Inspection: The inspection interval depends on the magnitude of the fault current. Immediate inspection is recommended after high-current faults.

 

Summary

Maintenance of outdoor high-voltage vacuum circuit breakers is a systematic process that cannot rely solely on a single method. A combination of "observation, listening, testing, and inspection" is key. Establishing comprehensive equipment records, recording test data, operation times, and maintenance history, and using data comparison to predict equipment status, is fundamental to transitioning from "scheduled maintenance" to "condition-based maintenance," thereby maximizing safe and reliable circuit breaker operation. All maintenance work must strictly adhere to safety operating procedures, ensuring safety measures such as power outages, electrical testing, and grounding.

 

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