E302 - Circuit Breaker & Transformer O&M (Low % Medium Voltage)

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2 days - 1.9 Continuing Education Units Awarded

Course Dates Download Brochure PDF
USD 995.00


Plant electricians, new engineers, mechanics (who work with and around electrical equipment) can gain significantly from this course.  This course provides fundamental knowledge of how the circuit breakers and transformers function and are maintained.  This fundamental knowledge is a critical piece of and O&M skills.  The course provides practical knowledge associated with how the devices are constructed, defining components the component purpose, and how it may be at risk.  This course also provides information on the skills necessary to implement a quality preventive maintenance program, to troubleshoot operational problems and corrective maintenance activities for the more common integrity issues.

Upon completion of this course, the participant should be able to:

  • Define those terms relevant to circuit breaker design and construction. Describe how inverse time-current characteristic can be applied to a circuit breaker.
  • Describe how a series trip and solid state trip units function and are tested.
  • List the protective devices found in a molded case breaker.
  • Explain how molded case trip devices are tested.
  • Describe the two basic types of low circuit breaker contacts.
  • Describe the five basic types of low circuit breaker operating mechanisms.
  • Describe the fundamental design, construction, application and operation of distribution transformers found in an industrial setting.
  • Describe transformer losses.
  • Describe various wiring connections such as wye/wye, wye/delta, and delta/delta.
  • Discuss aging and maintenance issues resulting from normal and abnormal operating conditions
  • Describe transformer preventive and corrective maintenance activities.
  • Describe safety considerations during maintenance activities.



  • Intro to LV & MV Switchgear:  Voltage Convention,  Switchgear,  Circuit Breakers,  Arcs & Arc Interruption
  • Circuit Breaker Construction:  Circuit Breaker Contacts,  Operating Mechanisms,  Molded Case Circuit Breakers
  • Types of Circuit Breakers – Air, Vacuum & Gas;  Introduction to Air Circuit Breakers,  Molded Case Circuit Breakers,  Intro to Vacuum Circuit Breakers,  Principles of Vacuum Circuit Breakers,  The Vacuum Interrupter,  Suphur Hexaflouride Gas Interruption.
  • Circuit Breaker Maintenance & Testing:  Contact Maintenance, Insulation Maintenance, Control Circuitry & Operating Mechanisms, Initial Testing, Routine Maintenance Testing, Special Maintenance Testing, Circuit Breaker Testing, Insulation Resistance Testing, Contact Resistance Testing, Hi Potential Testing, Power Factor Test, Breaker Motion Analysis
  • Low Voltage Protection Devices:  Basic Protective Device Requirements, Time Current Characteristics, Low Voltage Power Circuit Breaker Trip Devices, Protective Device Maintenance & Testing, Low Voltage Power Circuit Breaker Series Trip Unit Testing, Molded Case Circuit Breakers, Testing the Molded Case Circuit Breakers
  • Transformers: Transformer Principles, Vector Diagrams, Transformer Classifications, Transformer Connections, Transformer Maintenance
  • Insulation Resistance Testing; Insulation Resistance, Factors Affecting Insulation Resistance, Temperature Correction, Insulation Resistance Testing, Circuit Breaker Insulation Resistance Test, Non-Destructive High Potential Test
  • Power Factor Testing:  Advantages, Test Procedure, Interpretation of Test Data, Types of Tests
  • Instrument Transformer Testing:  Current Transformers, Potential Transformers



  • HPC Technical Services' fully illustrated textbook:  Circuit Breaker & Transformer O&M  (Low & Medium Voltage).
  • HPC's Certificate of Completion, including 1.3 Continuing Education Units.