Practical Power Transformers Operation, Maintenance and Testing

Introduction

Installation of high voltage distribution and transmission equipment has increased significantly over the years due to ongoing global demand for power. As a result, the need to ensure the reliability of the operation of power systems is paramount. It is critical that all personnel operating and working with such equipment have a sound knowledge of their operational requirements and maintenance.

WHAT’S INCLUDED?

• Four 50 minute live, practical sessions with your instructor and attendees
• The full technical eBook manual for “Practical Transformers: Operation, Maintenance, and Testing” which includes course slides, cases studies, calculations, and practical exercises
• Four hours of additional in-depth video sessions covering many additional areas – yours to keep and watch at your convenience

Objectives

Upon the successful completion of this course, each participant will be able to:-

• An understanding of the fundamental theory and principles of the operation of power transformers and transformer protection
• An insight into the identification and application of transformer types
• An understanding of power transformers, oil, and oil tests and interpretation of results
• Skills on how to manage power transformer breakdowns to ensure minimum disruption

Training Methodology

This is an interactive course. There will be open question and answer sessions, regular group exercises and activities, videos, case studies, and presentations on best practice. Participants will have the opportunity to share with the facilitator and other participants on what works well and not so well for them, as well as work on issues from their own organizations. The online course is conducted online using MS-Teams/ClickMeeting.

Who Should Attend?

This course is intended for Consulting engineers, Electrical contractors, and inspectors, electrical engineers and technicians, Power system engineers and technicians, Project engineers, Tradesman electricians, Utility engineers.

Course Outline

Day 1: POWER TRANSFORMER OIL AND OIL QUALITY

• Oil contents: water, acidity, and dissolved gas
• Oil tests: dielectric breakdown, moisture, resistivity, interfacial tension, specific gravity, power factor, furan analysis
• Recovery voltage measurement test

POWER TRANSFORMER PROTECTION

• Surge protection
• Protective relaying (differential, over-current, and earth fault)
• Buchholz relay and pressure relief relay
• Thermal devices and instruments (oil temperature alarm and trip, winding temperature alarm and trip)
• TRANSFORMERS’ MAIN FUNCTIONS AND CLASSIFICATION
  • Construction (shell type and core type)
  • Classification and type in relation to insulation, windings, core, cooling systems, voltage level, sizing, tank and breathing action Transformer parts

Day 2: POWER TRANSFORMER ELECTRICAL TESTS

AC Tests:

• Power factor tests (insulation, oil, and bushings)
• Single phase excitation current test
• Transformer turns ratio test

DC Tests:

• Insulation resistance test
• Dielectric absorption test
• Polarisation index test
• Step voltage test
• Hi-pot test

DAY 3: AUTO-TRANSFORMERS

• Design criteria
• Specifications

GENERATOR TRANSFORMERS

• Design criteria
• Specifications

POWER TRANSFORMERS AND SAFETY

• How to install, operate and work with high voltage power transformers safely
• Earthing of HV transformers

DAY 4: TAPPINGS AND TAP CHANGERS

• Uses of tap changers
• Impedance variation
• Tap changer mechanisms
• On-load tap changing by reactor transition
• Diverter resistor tap changers o In tank type tap changers
  • Externally mounted tap changers
• Off-circuit tap changers
• Construction of tap changers
• Control of on-load tap changers o Master/follower control
  • Circulating current control
  • Runaway prevention
• Moving coil regulator
• The Brentford linear regulating transformer
• Preventative maintenance guidelines
• Standards applicable to tap changers C57.131-1995
• Comparison between IEEE and IEC approaches
• TRANSFORMER THEORY
  • Electrical values and their definition in a power transformer - voltage, current, number of turns, impedance, and their interrelation

DAY 5: PREVENTATIVE MAINTENANCE ON POWER TRANSFORMERS

• Techniques to improve life expectancy

UNIT TRANSFORMERS

• Design criteria
• Specifications

STATION TRANSFORMERS

• Design criteria
• Specifications

OPERATION OF POWER TRANSFORMERS IN A POWER SYSTEM

• Thermal performance, loading, paralleling, tap-changing, connections and vector groups