INTRODUCTION: Operation, Maintenance, Testing and Monitoring of Large Power Transformers


IzzyTech sponsors a 3-day technical workshop: “Principles of Operation, Maintenance, Testing and Monitoring of Large Power Transformers”.  This workshop is an introduction to the construction, selection, application, operation, maintenance, and protection of larger power transformers.

Target Audience

People that will greatly benefit from this seminar include: power plant operators, engineering and management; repair shop personnel; transmission and distribution personnel working with large power transformers; personnel working with power transformers in other industries; new technical employees with little or no previous experience with large power transformers; and nuclear system and protection engineers with responsibility for the operation and maintenance of large power transformers.

Presenter: Dr. Izzy Kerszenbaum

Course Syllabus

Why Transformers are Required in Power Systems

  • Characteristics of AC circuits
  • Voltage and current changes introduced by the transformer
  • Economical and technical benefits from the application of transformers
  • Numerical examples of the influence of voltage levels on transmission costs and power transfer capabilities.

Transformer Basic Theory

  • Magnetism
  • Electricity
  • Faraday’s Law
  • The “ideal” transformer
  • The “non-ideal” transformer.
  • Windings
  • Conductor material
  • Insulation materials
  • Types of coil-construction
  • Coil manufacturing
  • Strand transposition
  • Coil blocking

Transformer Design and Construction

  • Number of phases
  • Cores
  • Types of cores
  • Core steels
  • Core assembly
  • Type of core junctions
  • Core hysteresis losses
  • Core eddy loses.

Tap Changers

  • Purpose of using tap-changers
  • Types of tap-changers
  • Operation of a typical tap changer


  • Total enclosed units
  • Ventilated units
  • Oil-filled units

Flux and Shunt Shields

  • Purpose of flux and/or shunt shields
  • Description of the operation of the flux shield
  • Description of the operation of the shunt shield


  • Arrhenius curves
  • Cooling by radiation
  • Cooling by convection
  • Cooling by conduction
  • Heat exchangers
  • Oil pumps
  • Water-cooled transformers

Terminal Connections and Current Transformers

  • Different Arrangements of terminal connections

Bushings and Lightning Arrestors

  • Medium voltage bushings
  • HV bushings
  • Maintenance of bushings
  • Types of bushings
  • Infrared scanning
  • Lightning and surge arrestors

Keeping Moisture Out of Transformers

  • Free breathing transformer
  • Pressurized breathing transformer
  • Nitrogen blanket
  • Auxiliary sealing system
  • Free-breathing conservator
  • Conservator with bladder
  • Importance of keeping moisture out of transformers
  • Estimating water content in oil and insulation paper

Terminal Markings and Vector Diagrams

  • Transformer polarity
  • Single-phase terminal markings and connections
  • Three-phase banks made of single-phase units
  • Three-phase unit terminal markings
  • Vector diagrams Transformer rating definitions
  • Class and BIL

Typical Tests

Types of Failures

  • Transportation
  • Electrical
  • Mechanical
  • Thermal
  • Shorted turns
  • Description of monitoring and protecting devices

Calculating Optimal Turns Ratio By Way of an Example

Calculating Transformer Remaining Life

Dissolved Gas-Oil Analysis (DGA)

Physical-Chemical Analysis (PCA)
Review of a number of real failures