Self-Paced Technical Seminars: Transformers

Diego Robalino, Megger and Nick Perjanik, WEIDMANN Electrical Technology Inc.

Transformer manufacturers working together with insulation material suppliers aim to deliver the most reliable and suitable product for the specific application where a power transformer will reside within the power system electrical infrastructure. In order to accomplish this complex task, a sequence of procedures has been put in place to assure quality of the manufacturing process and assembly of every single component.

In order to maintain a reliable operation, asset managers assign on-line and off-line testing procedures to evaluate the condition of power transformers in the field. It is so critical and important to understand the information that can be acquired in the field by off-line testing, and to correlate this information with laboratory analysis. The application of DC and AC diagnostic techniques in the field are well described in the first part of the seminar. Attendees will be able to review latest development in Power Factor Testing and Dielectric Frequency Response.

Because the opportunity to de-energize a power transformer is not a simple task and not often to happen, the second part of this seminar is focused on routine laboratory analysis of liquid insulation. Oil sampling practices, key laboratory tests performed by specialized personnel are used for overall condition assessment of the transformer. A brief but clear description of the importance of each of these laboratory tests in the context of this seminar.

The information is of great importance for asset managers, manufacturing OEMs, field operations staff, testing service companies and other interested parties. The seminar follows major national and international standards including ASTM, IEEE and NETA.

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Jim White, Shermco Industries, Inc.

Generator protection presents unique challenges to the testing technician. This presentation provides a basis for a higher quality testing by explaining the underlying application, common schemes, and presenting effective testing strategies for commonly encountered generator protection elements. Overexcitation, over voltage, stator ground, reverse power, loss of field, over current, fuse loss, out of step, over/under frequency, and differential functions will be covered.

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Melvin Wright, LICA Consulting, LLC

This session examines the proper sampling techniques, sample containers, tests performed on transformer oils, the diagnostic value of each test and how to evaluate the quality and condition of the fluid for transformer dielectric fluids. This course also examines how dissolved gas analysis (DGA) and furans are used to evaluate transformer faults and the operational condition assessment of transformers.

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Charles Sweetser, OMICRON electronics Corp. USA

This seminar will provide an overview of the essential information needed to determine the condition of power transformers.

Participants will learn:

• Transformer theory
• Diagnostic test methods
• Data analysis strategies
• Application of electrical measurements will be discussed including:
  • Power Factor and Capacitance
  • Excitation Current
  • Transformer Turns Ratio
  • DC Winding Resistance
  • Impedance: Leakage Reactance/ FRSL
  • DGA/Oil Screen
  • Sweep Frequency Response Analysis (SFRA)
  • Moisture Estimation- Dielectric Frequency Response

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Jim White, Shermco Industries, Inc.

No moving parts - no need for maintenance, right? Unfortunately, for many companies, the truth is a rude shock. Transformers are a critical part of any power distribution system. If they go down, everything they feed is out of service, sometimes for months. This seminar covers the primary types of tests used for maintenance and diagnostics, including insulation power factor, winding resistance, excitation current, ratio testing, and an overview of dc tests for dry-type and small transformers. Also covered will be factory tests, expected results, and their significance.

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Mike Wolf and Mike Anderson, Doble Engineering Company

When testing transformers, a working knowledge of the “meaning” behind the test results can allow the tester to identify possible setup problems, undertake troubleshooting steps, and ultimately make a smart decision about the health of the transformer. This presentation will review the theory and data interpretation of common transformer tests including power factor and capacitance, excitation, turns ratio, and winding resistance. The main focus of the presentation will be on reviewing case studies to illustrate the defects and damage that can be discovered during testing.

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