Electrical Transformer Operational Principles, Selection, Testing, Maintenance& Troubleshooting

Course Overview:

Power 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 rating transformers can have operating voltages up to several hundreds of kilovolts. Other types of transformers include instrument transformers, industrial transformers, testing transformers, and other special types.

Power and distribution transformers represent a major asset of the power utility. Failure of a transformer can be very costly not only because of the damage to the transformer itself but also because of the ramifications of such failure. This may include disruption of supply, explosions, or fire damage. It is therefore paramount that power transformers are properly operated and maintained.

The design of any transformer must fulfill certain requirements in order to withstand the electric, thermal, and mechanical stresses during its service life. These requirements are detailed in the relevant standards together with any special conditions outlined in the specifications of the purchaser of the transformer.

Tests 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.

Course Objectives:

By the end of the training, participants will be able to: –

• Apply transformer operating principles
• Able to understand in detail the basic working principles of transformer.
• Gain knowledge of practical solutions for specifying, operating, and maintaining power transformers in a utility or plant environment
• Able to monitor and operate transformers in accordance with the right standard operating procedure (SOP).
• Avoid costly errors by specifying the wrong transformer for your application
• Able to perform the right approach to transformer maintenance.
• Examine the possibilities of maximizing the efficiency and economic performance of your transformer fleet
• Determine transformer specifications to suit various applications
• Able to identify faults and troubleshoot transformers.
• Able to reduce downtime due to failure of the transformer.

Who Should Attend?

This course is designed for Electrical engineers, Maintenance, and operation

Course Contents:

Module (01) 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

Module (02) Power Transformers

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

Module (03) Distribution Transformers

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

Module (04) Types and rating of the transformer

• Oil Immersed Type
• Dry-type (Including phase shifting transformer)
• Sealed type

Module (05) Components of transformer and their functionalities

• Name Plate,
• Main Tank,
• Conservator Tank,
• Radiators,
• Cable Box
• Disconnection Chamber
• LV And HV Bushing,
• Transformer Mineral Oil,
• Dehydrating Breather, Bucholz Relay
• Tap Changer, Both on-Load and off-Load
• Laminated Core, Windings,
• Transformer Accessories.

Module (06) Transformer Connections

• The polarity of single-phase transformers
• The 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
• Paralleling of transformers

Module (07) Transformer Protection

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

Module (08) Transformer Installation

• Transformer installation
• Sample transformer acceptance checklist

Module (09) Testing Transformers

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

Module (10) 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

Module (11) Conditional Base Monitoring of Maintenance (Predictive Maintenance)

• Check and inspect the status of performance.
• Check the life history of the transformer (Installation record)
• Diagrams, details of operational limitations due,
• Maintenance record, number of failures that have occurred,
• Average maximum temperature, efficiency)