Power and distribution transformers are essential devices in electricity supply. Their ratings can vary from small size distribution transformers of a few kVA up to very large power transformers of 1000 MVA or more. In terms of voltage ratings transformers can have operating voltages up to several hundreds of kilovolts. They represent a major asset of the power utility and any industrial plant. 

Failure of a transformer can be very costly and dangerous for other major equipment and personnel alike. The design and operation of any transformer must fulfill certain requirements in order to withstand the electric, thermal and mechanical stresses during its service life. Tests and maintenance of transformers according to the relevant standards are intended to ensure that a transformer passing them will give trouble-free service for many years under the conditions it is likely to experience after its installation.

At the end of the course participants will able to:

• Refresh the knowledge of the basic theory of transformers

• Understand the principles of operation of the transformer

• Identify the different features of power transformers, distribution transformers and instrument transformers

• Appreciate the principles of transformer design, ratings, windings, core structure and materials, insulation and cooling methods, selection, insulation, and lifetime

• Be familiar with construction of the transformer, transformer winding connections

• Recognize the effects of transformer load changes and off-load and on-load tap changers

• Understand transformer troubleshooting

• Engineers and Technicians from electricity supply industry

• Technical Management Professionals and Department Leaders

• Engineering Professionals from companies manufacturing and operating power and distribution transformers

• Engineers and Technical Personnel in power utilities, petrochemical plants, service professionals of large infrastructure projects.

• Participants need no specific requirements other than basic understanding of electricity and magnetism and circuit theory and general knowledge of nature and operation of power and distribution transformers.

Day 1:

Introduction, General Principles and Classification 

• General Classification of Transformers: Transformer Construction, Core-Type, Shell-Type, Dry-type Transformers, Oil-filled Transformers, Cooling Techniques

• Transformer Windings, Interconnection of Windings, Advantages and Disadvantages of Principal Connections. Tertiary Windings, Autotransformers

• Harmonics in Transformers, Parallel Operation of Transformers, Loadings of Transformers in Parallel, Paralleling Requirements, Polarity

• Standards for Transformers, Types and Requirements

• Transformer Tapping and Connections

• Ability to withstand Short Circuit, Sound Level

• Case studies and workshop discussion



Day 2:

Transformer Constructional Details 

• Transformer Oil, Characteristics, Oil Oxidation, Breakdown Voltage, Water Content, Acidity, Oil Testing, Field Oil Testing, Dissolved Gas Analysis, Treatment and Filtering of Oil

• Effect of Oil Expansion, Breathing Action, Buchholz Relay, Explosion Vents

• Instrument Transformers

• Transformers for Industrial Applications: Electro-chemical, Arc and Induction Furnaces, Rectifier Transformers, High Voltage Testing Transformers, Precipitator Transformers, Dry Type Transformers

• Construction And Details, Transformer Cooling, Natural Cooling, Forced Cooling

• Case studies and Workshop Discussion



Day 3: 

Transformer Operation, Selection, and Maintenance 

• Distribution Voltage Adjustment, Off-Load Tap Changing, On-Load Tap Changing

• Switching of high voltage underground cables supplying Distribution Transformers

• Earthing and Over-Current Protection of Distribution Transformers

• Transformer Maintenance: Oil p reservation , Deterioration of oil, Breathers, Condition Monitoring, Faults in Transformers, Tapping and Windings

• Advanced Transformer Maintenance

• Guidelines on how to care for your Distribution Transformer

• Case studies and Workshop Discussion



Day 4:

Transformer Connections 

• Single Phase Circuits 

• Two-Phase Circuits 

• Three-Phase Circuits 

• Transformer Maintenance and Troubleshooting 

• Insulation Testing 

• High Potential Testing 

• Turns Ratio Testing 

• oPolarity Testing 

• Power Factor 

• Excitation Current 

• DC Winding Resistance 

• Polarization Recovery 

• Insulating Fluid Dielectric 

• Dissolved Gas Analysis



Day 5: 

Transformer Protection, and Relaying 

• Transformer Faults and Troubleshooting 

• Differential Relaying 

• Normal Load 

• External Faults 

• Internal Faults

• Case studies and Workshop Discussion