Transformer Maintenance

Bijan Ghayour, P.E.

Course Outline

This 10-hour course provides basic engineering guidance in maintenance, diagnostics, and testing of power transformers and associated equipment. The contents cover the basics of power transformers cooling methods, i.e. dry type versus liquid-filled transformers. Components of each of these transformer categories are defined and the potential problems and remedial actions are discussed.

This course has been developed from ANSI/IEEE standards, the evaluation of the existing facilities, and from surveys of the many existing power transformer which have been put into service in the last seventy years.

The course materials are based entirely on the Unified States Department of the Interior, Facilities Instructions, Standards, and Techniques Volume 3-30.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of course materials.

Learning Objective

The purpose of this course is to provide guidance for the maintenance engineers in maintenance, diagnostics, and testing of power transformers and associated equipment

At the conclusion of the course the student will be familiar with the:

• Typical faults in power transformers;
• Transformer test summary;
• Doble and IEEE physical test limits for service-aged silicone fluid;
• Doble limits for in-service oils;
• Transformer cooling methods and systems;
• Dry type transformers;
• Dry type transformer maintenance summary;
• Liquid-filled transformers;
• Oil-filled transformer maintenance summary;
• Potential problems and remedial actions for dry type transformers cooling system;
• Potential problems and remedial actions for liquid-filled transformers cooling systems;
• Cooling system inspections;
• Oil-filled transformer inspections;
• Transformer oil functions;
• Dissolved gas analysis (DGA);
• Key gas method;
• Actions based on dissolved combustible gas;
• Transformer diagnosis using individual and total dissolved key gas concentrations;
• Rogers ratio method of DGA;
• Moisture problems;· Dissolved moisture in transformer oil;
• Moisture in transformer insulation;
• Transformer oil tests that should be done annually with the dissolved gas analysis
• Dielectric strength;
• Interfacial tension (IFT);
• Acid number;
• Test for oxygen inhibitor;
• Power factor;
• Furans;
• Procedures for taking oil samples for DGA;
• Silicon oil-filled transformers;
• Winding resistance testing;
• Core insulation resistance testing; and
• Inadvertent core ground testing.
  
  

Intended Audience

This course is intended for electrical engineers and maintenance personnel involved in the service and maintenance of power transformers.

Benefit to Attendees

The student will become familiar with the general guidelines and techniques of inspection and testing of power transformers. Items discussed include different cooling methods and systems for power transformers and the potential problems and remedial actions needed for each type. This course also included tables for recommended maintenance schedule for dry and oil-filled transformers.

Course Introduction

Power transformers have typical life of 20 to 25 years. With proper inspection, testing, and maintenance the life of a transformer can extended well beyond this limit. Power transformer are major and vital part of any power generation and distribution systems, and are essential in providing reliable power to industry, government and residential customers. The minimum replacement time is around 14 months; a more realistic time may be 18 months to two years.

This course provides practical information in testing and inspection of power transformers. The course also offers practical information in mitigating the problems associated with different type of transformers. It is understood that with proper testing and scheduled inspection many of the transformer problems can be diagnosed in advance and by taking remedial actions the life of the transformers can be extended resulting in less capital expenditure and reliable service.

Course Content

This course contains specific examples, with practical emphasis on the inspection, testing, and maintenance of power transformers.

You are required to study volume 3-30, Transformer Maintenance, published by the Unites States Department of the Interior, Bureau of Reclamation.

FIST 3-30 Transformer Maintenance (PDF File 1.5 MB)

(For an electronic copy of FIST 3-30 go to http://www.usbr.gov/power/data/fist/fist3_30/fist3_30.pdf)

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

The following contains the outline of the FIST 3-30 of Department of Interior, Bureau of reclamation:

FIST 3-30 Transformer Maintenance (PDF File 1.5 MB)

Table of Contents

1- Purpose

2- Introduction to Reclamation Transformers

3- Transformer Cooling Methods

• Dry Type Transformers
• Liquid-Immersed Transformers
• Oil-Filled Transformer Inspections
• Oil-Filled Transformers
• Oil Preservation Sealing Systems
• Gaskets
• Transformer Oils
• Moisture Problems
• Transformer Oil tests That Should Be Done Annually With the Dissolved Gas Analysis
• ransformer testing

4- References

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

---

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.

---