What are the maintenance methods for outdoor high-voltage vacuum circuit breakers?

Proper maintenance of outdoor high-voltage vacuum circuit breakers is crucial for ensuring the safe and reliable operation of the power grid.

Core Principle: Safety first; strictly adhere to operating procedures; operations must be performed by certified professional electricians.

The following is a detailed overview of the maintenance methods for outdoor high-voltage vacuum circuit breakers, which can be divided into three main parts: pre-maintenance preparation, daily inspection, and periodic maintenance.

I. Preparatory Work Before Maintenance

 

Work Permit Issuance: Strictly adhere to the "two-permit, three-system" approach, issuing a power outage work permit and ensuring the equipment is completely out of service.

Safety Measures:

Reliable Power Outage: Disconnect the circuit breaker and its two disconnecting switches, ensuring the circuit breaker is in the open position.

Electrical Testing and Grounding: Use a qualified voltage detector to test the voltage on each phase of the circuit breaker's incoming and outgoing lines. After confirming no voltage, immediately install a grounding wire.

Issuing Signs: Hang signs such as "Personnel Working, Do Not Close" and "Working Here" on the operating mechanism and the handles of disconnecting switches that may be energized.

Establish Fence: Set up a temporary fence at the work site to prevent unauthorized personnel from entering.

Personnel and Tools:

Maintenance personnel must be familiar with the structure, principle, and performance of this type of circuit breaker.

Prepare a complete set of specialized tools and instruments (such as megohmmeters, multimeters, torque wrenches, lubricating grease, etc.) and personal protective equipment (insulating boots, insulating gloves, safety helmets, etc.).

 

II. Routine Inspection (Uninterrupted Power Supply, Visual and Operational Status Check)

 

This is the foundation of preventative maintenance, primarily relying on visual inspection, listening, and simple instruments.

Visual Inspection:

Enclosure: Check for rust, deformation, damage, and poor sealing (especially the rain cover).

Bushelves and Insulators: Check for cracks, damage, severe contamination, and discharge traces.

Markings: Check that nameplates, opening/closing indicators, etc., are clear and intact.

Operating Status Check:

Indication Position: Check that the opening/closing mechanical indicators and energy storage indicators match the actual conditions.

Abnormal Noises: Listen at a safe distance for any abnormal sounds such as discharge sounds or vibrations within the circuit breaker body and mechanism box.

Air/Hydraulic Pressure: For hydraulic or SF6 mechanisms, check that the pressure gauge readings are within the normal range.

Lead Connections: Check that the primary leads and grounding wire connections are secure and that there are no signs of overheating or discoloration (an infrared thermometer can be used).

 

III. Regular Inspection and Maintenance (Power Outage Inspection)

 

This is the core of maintenance and is usually carried out in conjunction with preventative tests (such as withstand voltage tests, circuit resistance tests, etc.). The cycle is generally 1-3 years or based on the number of operations (such as 2000 times).

1. Vacuum Interruptor (Vacuum Bulb) Inspection

Vacuum Degree Testing: This is the most critical step. It is usually tested using the power frequency withstand voltage method. Apply the rated power frequency withstand voltage (e.g., 42kV for a 12kV circuit breaker) between the contacts and hold for 1 minute. If there is no flashover or breakdown, the vacuum degree is good. Disassembly of the vacuum bulb for inspection is strictly prohibited.

Visual Inspection: Observe the glass or ceramic casing for cracks and stains, check the internal metallic luster for normality, and look for oxidation or discoloration.

 

2. Operating Mechanism Maintenance

Energy Storage Mechanism:

Spring Mechanism: Check the springs for rust and deformation. Clean and lubricate the transmission components with the closing/opening springs in an un-energized state.

Electromagnetic Mechanism: Check the closing contactor, armature, etc., for jamming and wear, and ensure smooth operation.

Permanent Magnet Mechanism: Check the capacitor bank and control board status, and measure the energy storage capacitor capacity.

Transmission Linkages: Inspect all linkages and crank arms for deformation and cracks, and ensure all connecting pins are present and secure.

Lubrication: Clean and re-lubricate all rotating and sliding parts (such as bearings and pins) with a special low-temperature grease. Be careful not to use excessive amounts, and remove old grease and dust.

Tightening: Use a torque wrench to tighten all screws and nuts (especially those in the main circuit connections and internal mechanisms).

 

3.Primary Circuit Inspection

Main Circuit Resistance Measurement: Use a circuit resistance tester to measure the contact resistance between the circuit breaker contacts. The measured value should conform to the manufacturer's specifications (usually very low, such as ≤40μΩ) and be compared with historical data. An increase in resistance indicates contact wear or loose connections.

Insulation Inspection: Use a 2500V or 5000V megohmmeter to measure the insulation resistance between contacts, to ground, and between phases. The measurement should conform to standards.

Contact Inspection: Indirectly assess contact wear by observing circuit resistance values ​​and mechanical characteristics such as contact gap and overtravel. When the wear reaches the manufacturer's specified value, the vacuum interrupter should be replaced.

 

4. Secondary and Control Circuit Maintenance

Terminal Block Inspection: Check all terminals for looseness and oxidation, and tighten them one by one.

Auxiliary Switches (Microswitches): Check contacts for burning and ensure accurate and reliable operation. Use a multimeter to measure continuity.

Closing/Opening Coils: Check coils for overheating and burning marks. Measure their DC resistance; it should be within acceptable limits.

Secondary Circuitry: Check control cables and wires for good insulation and no damage.

 

5. Mechanical Characteristics Test (Very Important)

Measure the following parameters using a high-voltage switch characteristic tester and compare them with factory values ​​or the data from the last test:

Opening/Closing Time

Opening/Closing Speed

Contact Distance

Contact Overtravel

Three-Session Synchronization (Opening and Closing Synchronization)
These parameters directly affect the circuit breaker's breaking and closing performance.

 

IV. Post-Maintenance Work

 

Clean Up the Site: Inventory tools and remove debris and waste grease from inside the equipment box and the surrounding area.

Remove Safety Measures: Remove grounding wires, signs, etc.

Manual/Electric Operation Test: Under the premise of ensuring personnel safety, perform several manual and electric opening and closing operations to confirm that the operation is flexible, the indication is correct, and there are no jamming or abnormal noises.

Records and Reports: Record in detail the maintenance content, test data, problems found, and their handling results, and store them in the equipment file.

 

Summary

 

Through the above systematic maintenance, the service life of outdoor high-voltage vacuum circuit breakers can be greatly extended, ensuring their reliable operation at critical moments and protecting personal and equipment safety.

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