**Operation and Maintenance of SF6 Circuit Breakers**
1. **Safety Precautions**
During the operation and maintenance of SF6 circuit breakers, it is essential to follow the safety regulations outlined in DL/T 639-1997. Personnel must be well-trained and equipped with appropriate protective gear to ensure safe handling of SF6 gas and electrical equipment.
2. **Routine Inspection During Operation**
Regular checks are crucial to maintain the performance and safety of the circuit breaker. The following points should be carefully examined:
- Check the external insulation (porcelain sleeve) for cracks, damage, dirt, or signs of flashover.
- Monitor the pressure gauge or density controller using the temperature-pressure curve. Record pressure and temperature values periodically.
- Ensure the position indicators and closing status are correct, and the contacts are properly engaged.
- Inspect all fasteners for looseness or detachment.
- Listen for any unusual noises from the energy storage motor or the circuit breaker itself.
- Check the closing and tripping coils for any signs of burning, smoke, or discoloration.
- Verify that the grounding of the enclosure or bracket is intact.
- Confirm that the housing and operating mechanism box are free from corrosion and damage.
- Inspect the circuit breaker for physical damage, deformation, or severe rusting.
3. **Maintenance Procedures**
To ensure long-term reliability, the following maintenance tasks should be performed regularly:
- Apply anti-corrosion treatment to any rusted areas annually.
- Lubricate the circuit breaker and its moving parts every six months. Perform three operational tests after lubrication.
- Conduct a qualitative leak test on all sealing surfaces every two years. No leakage above 10â»â¶ atm·cm³/s should be detected.
- Test the moisture content of the SF6 gas annually. The result should not exceed 300 ppm at 20°C.
- Perform other tests such as insulation and operation tests according to relevant standards.
- During maintenance, release the energy stored in the trip and close springs to avoid unexpected movement.
4. **Overhaul and Technical Parameters**
When overhauling, ensure that all technical parameters meet the specifications outlined in Table 1. This includes checking mechanical and electrical characteristics, ensuring proper alignment, and verifying the integrity of all components.
5. **Failure Analysis and Troubleshooting**
Common issues include gas leaks, low closing or opening speed, and moisture ingress. Here’s how to address them:
- **Leak Detection**: If the density relay signals a pressure drop, check for internal leaks or faulty wiring. Replenish gas if necessary, but avoid operating the breaker under vacuum conditions.
- **Low Closing/Opening Speed**: Adjust the stroke of the closing core, check for coil overheating, inspect auxiliary switches, and ensure all mechanical components are functioning smoothly.
- **Moisture Ingress**: Replace the desiccant and dry the system. If needed, replace the SF6 gas with new, high-quality gas.
6. **Dismantling and Overhaul**
If the circuit breaker has reached its mechanical life, accumulated breaking current limit, or shows abnormal behavior, it should be returned to the manufacturer for disassembly and overhaul. The process involves:
- Ensuring a clean, dry, and ventilated environment during maintenance.
- Wearing full protective gear, including gas masks and gloves.
- Properly disposing of SF6 gas and chemical waste through neutralization processes.
- Replacing worn or damaged parts such as seals, springs, and insulators.
- Reassembling the breaker and conducting vacuum testing before refilling with SF6 gas.
- Performing final checks to ensure compliance with factory standards.
**Note:** Always prioritize safety when working with SF6 equipment. Follow all manufacturer guidelines and local regulations to prevent accidents and ensure long-term performance.
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