doble M4110 User manual

Doble Engineering Company
85 Walnut Street
Watertown, Massachusetts 02472-4037
(USA)
PN 500-0396 72A-2243-01 Rev. B 9/04
September 17, 2004
M4110 Leakage Reactance
Interface User Guide

Copyright © 2004
By Doble Engineering Company
All Rights Reserved.
This Manual is the sole property of the Doble Engineering Company (Doble)
and is provided for the exclusive use of Doble Clients under contractual
agreement for Doble Test Equipment and Services.
In no event does the Doble Engineering Company assume the liability for any
technical or editorial errors of commission, or omission; nor is Doble liable for
direct, indirect, incidental, or consequential damages arising out of the use or
inability to use this Manual.
Government Restricted Rights Legend: Use, duplication, or disclosure by the
U.S. Government is subject to restrictions as set forth in subparagraphs (c)(1)
and (c)(2) of the Commercial Computer Software - Restricted Rights Clause at
FAR 52.227-19.
This manual is protected by copyright, all rights reserved, and no part hereof
may be photocopied or reproduced in any form without prior written consent
of the Doble Engineering Company.
Copyright
© 2004
By Doble Engineering Company
All Rights Reserved.

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September 17, 2004
Preface
Structure of this Manual
This manual consists of 4 chapters and two appendixes.
Chapter 1 “Introduction To Leakage Reactance Testing”
introduces the M4110 Leakage Reactance Interface.
Chapter 2 “Understanding Leakage Reactance Testing” provides
an overview of Leakage Reactance theory.
Chapter 3 “Leakage Reactance Test Procedures” describes
procedures for executing Leakage Reactance tests.
Chapter 4 “Interpretation Of Test Results” explains how to
analyze test results.
Appendix A “Voltage Selection” describes how to change the test
set input voltage from 115 volts to 220 volts.
Appendix B “Part Numbers” lists the parts of the M4110 Leakage
Reactance Interface.

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Conventions Used in this Manual
The following terms and typographical conventions are used in the manual:
Convention Description
Windows Refers to the Microsoft Windows operating system,
Version 95 or later.
Click Quickly press and release the left mouse button.
Double-click Quickly press and release the left mouse button twice
without moving the mouse.
Select Position the cursor on the desired option and click the
left mouse button once. Or, highlight the desired
option using the arrow keys and press ENTER. Or, press
ALT and the underlined letter.
Press Type a single keyboard key. For example, press ENTER.
FN+(appropriate key) Press and hold the FN key, and press (appropriate
key).
Bold Courier Text Indicates characters to be typed.

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1. Introduction To Leakage Reactance Testing
M4110 Leakage Reactance Interface ................................................................................................. 1-1
Installing the Software........................................................................................................................ 1-2
What You will Need for the Test........................................................................................................ 1-2
2. Understanding Leakage Reactance Testing
Introduction ........................................................................................................................................ 2-1
Failure Modes..................................................................................................................................... 2-3
How Results are Calculated................................................................................................................ 2-5
Three-phase Equivalent Test........................................................................................................ 2-5
Per-phase Test .............................................................................................................................. 2-5
Single-phase Two-winding Test...................................................................................................2-5
3. Leakage Reactance Test Procedures
Test Considerations ............................................................................................................................ 3-1
Information Needed Before Running a Test....................................................................................... 3-1
Test Voltages...................................................................................................................................... 3-2
Selecting the Test Method.................................................................................................................. 3-2
Special Considerations................................................................................................................. 3-3
Test Connections.......................................................................................................................... 3-3
Test Procedures for a Two-winding Three-phase Unit ...................................................................... 3-4
Three-phase Equivalent Test........................................................................................................ 3-5
Per-phase Test .............................................................................................................................. 3-5
Test Procedures for a Two-winding Single-phase Unit...................................................................... 3-5
Test Procedures for a Multi-winding Unit.......................................................................................... 3-5
Test Setup Using the M4110 or the M4130 ..................................................................................... 3-11
Setup for a Single-Phase Transformer Test, M4110.................................................................. 3-11
Setup for a Single-Phase Transformer Test Using the M4130................................................... 3-12
Setup for a Three-Phase Transformer Test Using the M4110 ................................................... 3-12
Setup for a Three-Phase Transformer Test Using the M4130 ................................................... 3-13
Setup for a Transformer with Three or More Windings ............................................................ 3-14
Running a Test.................................................................................................................................. 3-14

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4. Interpretation of Test Results
Initial Test...........................................................................................................................................4-1
Subsequent Test..................................................................................................................................4-2
Appendix A. Voltage Selection
Altering the Voltage Rating from 115 Volts to 230 Volts................................................................. A-1
Appendix B. Part Numbers

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1. Introduction to Leakage Reactance Testing
M4110 Leakage Reactance Interface
This optional interface contains the circuitry necessary to convert the voltage
and current, measured during a Leakage Reactance test on a transformer, into
a form that can be measured by the M4100 Instrument. It also contains a
variac so that the proper test voltage can be obtained. The Leakage Reactance
test cannot be made without either this Interface or the M4130 Leakage
Reactance Module, and the accompanying software. It also requires an M4000
Insulation Analyzer.
When using this interface, the standard M4000 safety switch and safety strobe
are used. The necessary current and voltage cables are provided for connection
to the transformer, along with the necessary software, so that this becomes a
self-contained kit for this test. The user is only limited by the size of the variac
provided.
Figure 1.1 M4110 Leakage Reactance Interface

Introduction to Leakage Reactance Testing
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Installing the Software
The Leakage Reactance test requires additional software, and is installed in the
same directory as the M4000 software. Run the installation program from the
Setup command. Once you have picked the directory, the software installs
itself with no dialog boxes. You will be able to run the Leakage Reactance test
from the M4000 software, or, if available, from the DTA software.
Advantages of using the DTA software include:
1. Your test data is stored in the same file with your power factor, exciting
current, turns ratio, oil quality and DGA, and other test data.
2. DTA has forms specifically designed for Leakage Reactance tests.
3. You can store your Leakage Reactance test data in the DTA Office
database for future reference.
4. You can easily pull up one file with the entire history of Leakage
Reactance tests for a given transformer.
For more information on using the Leakage Reactance test with DTA, see the
DTA manual.
What You will Need for the Test
Besides the M4110 Leakage Reactance Interface and its cables, you will need:
1. M4100 and its cables, including the M4100 and either the M4200c
Controller or a laptop computer with the M4000 and Leakage Reactance
software loaded.
2. Heavy jumper cables, needed to short-circuit the secondary for each test.
You will be injecting anywhere from a fraction of an ampere to 3 or so
amperes on the High Voltage side, so you must take into account the
transformer’s turns ratio and use jumpers that can withstand the expected
current on the Low Voltage side.
3. To match the nameplate impedance, the transformer must be tested on the
same tap positions as were used to obtain the nameplate value. This
information must be obtained from the nameplate, and the transformer
must be set to those tap positions before the test.
NOTE To switch between 115 volt and 220 volt operation, see Appendix A.
What follows in this manual is information on the theory involved, and what
exactly is being measured, test connections and test procedure, and finally, test
results analysis.

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2. Understanding Leakage Reactance Testing
Introduction
Winding deformation which leads to an immediate transformer failure may be
the result of several overcurrent events. The probability of overcurrent
conditions is not very high and, as a result, a transformer can remain in service
with partially deformed windings, although the reliability of such a
transformer is reduced. Many transformer failures begin with mechanical
deformation but eventually occur for electrical reasons. Consequently,
determining mechanical deformation should be given very serious
consideration. Even small changes in measured parameters should be treated
with the utmost respect.
Several methods have been used to detect winding deformation. They are:
• frequency response analysis
• Iow-voltage impulse test
• capacitance measurement
• leakage reactance measurement
Methods one and two have inherently very promising searching capabilities.
The relative sophistication of the instruments and the expertise required for
these measurements has yet to allow them to become “household tools” at
many utilities.
Capacitance measurements are performed as a part of the routine
AC-insulation tests and normally include all three phases. Capacitance
between the windings, and between each winding and the core/tank, is a
function of their geometric relationships, as well as the dielectric constants of
the intervening insulation. It is known that capacitance may exhibit minor
variations due to temperature changes or serious contamination.
Leakage reactance measurements are performed by short-circuiting the low
voltage winding. During that test, the reluctance encountered by the magnetic
flux is determined predominantly by the leakage channel (Figure 2.1).

Understanding Leakage Reactance Testing
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Figure 2.1 Leakage Channel
The leakage channel is the space confined between the inner surface of the
inner winding, the outer surface of the outer winding, and the bottom and the
top yokes. When winding distortion occurs, it changes the reluctance of the
magnetic flux path, resulting in a change of the measured leakage reactance.
The leakage reactance measurement is the simplest of all four tests. During
routine transformer test investigations, it is useful to perform both leakage
reactance and capacitance tests. The changes in both parameters will serve as a
reliable indicator of the winding distortion. Case studies comparing the results
of both measurements are presented in Minutes of the Sixty-First Annual
International Conference of Doble Clients, 1994, sec. 6-5.
It should be noted that the leakage reactance test does not replace the exciting
current measurement; the two are complementary. Leakage reactance is
influenced by the reluctance in the leakage channel, magnetizing current is
influenced by the reluctance in the transformer core and can detect shorted
turns in the windings, shorted core laminations, multiple core grounds and
problems with the LTC and NLTC.