How To Do The Vacuum Circuit Breaker Maintenance

The first step is testing which helps us to know if there are any major faults or if something requires repair or replacement. The testing of vacuum circuit breakers involves various types of visual, mechanical, and other tests which are discussed in detail below.

Visual Inspection

The visual check is the simplest and primary one. Various parts such as drive insulators and molded pole unit support can be checked visually for dirt and cracking. Similarly, the control circuit parts such as wiring and terminals can also be checked for their intactness. For testing dirt and dust in the operating mechanism, a visual check is there. Sometimes, along with visual inspection, one can also feel and sense to inspect the parts e.g., for checking the tightness of hardware or operating mechanism.

Vacuum Interrupter Integrity Test

The reliability of a vacuum circuit breaker depends upon the integrity of the vacuum and the internal dielectric strength. For checking both of them, vacuum interrupter testing is arranged. The vacuum circuit breaker testing procedure is also known as a hipot test because a high potential is applied during the testing. 

This one-minute ac high potential test is used to check the insulation integrity from the main circuit to ground, from the control circuit to ground, and between main circuit terminals. A successful withstand indicates the good functioning of the vacuum interrupters whereas a break-down indicates that there is a defective interrupter or interrupters that needed to be repaired or replaced.  

Mechanism Check

The mechanism check involves visual inspection of the mechanism for any loose parts such as rings, bolts, and others. The other parts of mechanism check can include measurement check, functional check, operational check, or a combination of these. The measurement check is required for the inspection of vacuum interrupters for the visibility of three contact erosion indicators and contact wipe measurement. 

For checking the smooth functioning of a motor, a functional test is required. Similarly, for excessive wearing or deformation of the operating mechanism, both visual and operational checks are required. Sometimes, for the checking of the correct and smooth operation of certain parts, closing, tripping of the circuit breaker, or manual charging is also employed.