Transformer Operational Principles, Selection and Troubleshooting

After participating in this course, you will be able to:

• Apply transformer operating principles
• Gain knowledge of practical solutions for specifying, operating and maintaining power transformers in a utility or plant environment
• Avoid costly errors from specifying the wrong transformer for your application
• Examine the possibilities of maximizing efficiency and economical performance of your transformer fleet
• Determine transformer specifications to suit various applications

Description
Transformers are major components of electrical power systems. This course combines theoretical and practical aspects of transformer design, operation, maintenance and troubleshooting. The course emphasizes the importance of the magnetic properties of the core design on the transformer’s operational performance and electrical properties. It addresses economic trade-offs of transformers in real-world applications.

Course Outline

• Power & Distribution Transformers
• Dry Type Transformers
• Transformer Connections
• Loading Power Transformers
• Auxiliary Equipment
• Load Tap Chargers (LTCs)
• Transformer Selection and Application
• Transformer Protection & Installation
• Maintenance and Troubleshooting
• Power Transformer Equipment Standards and Processes

Who Should Attend
Electrical engineering professionals who need to update their knowledge • Distribution System Planners • Maintenance Managers • Power System Consultants • Participants should have a basic understanding of power system operations, but do not necessarily have to be experts • Engineers who are starting their career in the field of power in utilities, industrial or commercial plants and institutional complexes will benefit from this course.

Day I

Welcome, Introduction, Workshop Preview, Learning Outcomes and the Assessment Method

Basic Transformer Theory

• Currents and magnetic fields
• Air core transformer
• The magnetic circuit
• The B-H curve
• Hysteresis, and eddy current losses
• Iron or steel core transformer
• Equivalent circuit of an iron core transformer
• The practical transformer
• Magnetizing currents and harmonics
• Voltage considerations
• Thermal considerations

Power Transformers

• Rating and classifications
• Short circuit duty
• Efficiency and losses
• Construction
• Accessory equipment
• Inrush current
• Modern and future developments

Distribution Transformers

• Construction
• General transformer design
• Transformer locations
• Transformer losses
• Performance
• Transformer loading
• Special tests
• Protection
• Economic application

Underground Distribution Transformers

• Vault installations
• Surface operable installations
• Pad mounted distribution transformers

Dry Type Transformers

• Dry type transformers

Transformer Connections

• Polarity of single-phase transformers
• Angular displacement of three-phase transformers
• Three-phase transformer connections - advantages and disadvantages of the Y-Y connection, the Y-delta and delta-Y connection, the Y-delta grounding bank, zigzag connections, comparisons of economy, three phase banks using single phase transformers, transforming two-phase voltages into three-phase voltages, the scott-connected connection, autotransformers and three-winding transformers
• Parallelling of transformers

Adjournment

Day II

Loading Power Transformers

• Design criteria
• Nameplate ratings
• Other thermal characteristics
• Thermal profiles
• Temperature profiles
• Temperature measurements
• Predicting thermal response
• Load cyclicality
• Water in transformers under load
• Voltage regulation
• Loading recommendations

Auxiliary Equipment

• Bushings types, standards, design parameters, and testing
• Oil preservation systems
• Cooling equipment
• Temperature and oil level gauges

Load Tap Chargers (LTCs)

• Design and applications of load tap changers
• Rated characteristics and requirements for load tap changers
• Selection of load tap changers
• Maintenance of load tap changers
• Refurbishment replacement of old LTC types

Transformer Selection and Application

• Most economical transformer for your application

Transformer Protection

• Fuses and relays
• Gas relays
• Differential protection
• Code requirements

Transformer Installation

• Transformer installation
• Sample transformer acceptance check list

Testing Transformers

• Standards, and classification of tests
• Sequence of tests
• Voltage ratio and proper connections
• Insulation condition
• Dielectric withstand
• Performance characteristics
• Other tests

Adjournment

Day III

Maintenance and Troubleshooting

• Sample operating and maintenance instructions
• Preventative maintenance and predictive maintenance
• Gas in oil analysis
• Water in oil analysis
• Drying techniques
• Oil dielectric tests
• Sample transformer maintenance checklist
• Problem and failure investigations
• Problem analysis after severe operating conditions where no failure is involved - failure investigations

Power Transformer Equipment Standards and Processes

• Major standards organizations
• Process for acceptance of American National Standards
• Relevant power transformer standards documents

On-Line Monitoring of Liquid-Immersed Transformers

• Benefits
• On-line monitoring systems
• On-line monitoring applications

Questions and Answers and Feedback to Participants on Achievement of Learning Outcomes

Concluding Remarks and Final Adjournment