June 9, 2018 by Greg Carter

Testing Low Voltage Circuit Breakers

Low Voltage Circuit Breaker Testing and Inspection

1.0   INITIAL TEST AND INSPECTIONS

1.1      REQUIRED JOB FORMS

The tech should start the job by reviewing the Work Order and then completing the Planning Work Sheet with the work leader or supervisor. The tech should post the Work Order with supporting technical information, a Process Control Form, and a Material Transfer Form at his/her workstation.

1.2      LOW VOLTAGE CIRCUIT BREAKER DATA SHEET

A Low Voltage Circuit Breaker Data Sheet should be completed prior to disassembly. High current testing is not required unless the trip units are to be reused. Megger testing is required on all breakers to determine the initial condition of the pole pieces and insulators.

1.3      VISUAL INSPECTION

Remove the circuit breaker arc chutes and phase barriers to perform a complete visual inspection of moving main and arcing contacts, and stationary main and arcing contacts. Make any comments on the Low Voltage Circuit Breaker Data Sheet as to the general condition.

1.4      MECHANISM INSPECTION

Operate breaker manually, closing and tripping, inspecting and operate for proper contact wipe, worn or broken mechanism parts. Make any comments on worn or broken parts on the Low Voltage Circuit Breaker Data Sheet.

1.5      ELECTRICAL CONTROL INSPECTION

Verify that the proper schematic or wiring diagram is available for the breaker. Operate the circuit breaker electrically if possible, inspecting for proper operation of all auxiliary electrical devices, such as secondary disconnects, auxiliary switches, closing motors or solenoids, closing relays and tripping coils for defects. If unable to operate circuit breaker electrically, inspect all electrical components separately for proper operation recording any deficiencies on the Low Voltage Circuit Breaker Data Sheet and report to supervisor.

1.6      PARTS REPLACEMENT

Any parts needed, should be highlighted on the IT&I Parts Required Form and given to Inventory Control requesting these parts. When the parts are provided, the tech should log the parts on the Material Transfer Form.

1.7      QC INSPECTION

Initial and date the Process Control Form. Get inspector to initial and date the Process Control Form for initial inspection.

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