Vacuum Circuit Breakers

Steps for Servicing a Vacuum Circuit Breaker

1. Visual Inspection

   • Check insulators, pole unit support, control circuit parts, wiring, and terminals for dirt and cracks.
   • Inspect hardware and operating mechanisms for tightness and proper condition.

2. Vacuum Interrupter Integrity Test

   • Perform a high potential (hipot) test to check insulation integrity.
   • Assess dielectric strength and identify any defective interrupters.

3. Mechanism Check

   • Inspect for loose parts, perform measurements, and conduct functional and operational tests.
   • Check contact erosion indicators and motor functionality.

4. Insulation Maintenance

   • Clean insulation surfaces with a lint-free cloth or mild solvent.
   • Ensure surfaces are dry before reassembly.

5. Lubrication

   • Apply light machine oil annually or as needed.
   • Operate the breaker manually and electrically to distribute oil.

6. Troubleshooting

   • Address closing problems by checking alignment and replacing faulty parts.
   • Resolve tripping issues by replacing non-functional components.

7. Isolation and Cleaning

   • Turn off and isolate the VCB before maintenance.
   • Clean with electrical contact cleaner and re-grease with similar type grease.

8. Contact Inspection

   • Examine fixed and floating contacts for condition and proper positioning.

9. Hardware Check

   • Ensure all external parts and hardware are properly fixed.

10. Functional Testing

    • Use the push button to verify breaker tripping.

11. Electrical Testing

    • Measure current between phases and between phase and earth in both closed and open states.