Megger TTR25 User manual

AVTMTTR25
Rev. C
April 2008
Instruction Manual AVTMTTR25
for
TTR25 Handheld TTR®
Transformer Turn Ratio Test Set
Catalog No. TTR25
High-Voltage Equipment
Read the entire manual before operating.
Aparato de Alto Voltaje
Antes de operar este producto lea este manual enteramente.
M
2621 Van Buren Ave
Norristown, PA 19403-2329
610-676-8500
www.megger.com

TTR25 Handheld TTR®
Transformer Turn Ratio Test Set
Instruction Manual

Copyright Notice
Copyright©2005 by Megger. All rights reserved.
Disclaimer Notice
The information contained in this manual is believed to be adequate for the
intended use of the product. If the product or its individual instrument are used for
purposes other than those specified herein, confirmation of their validity and
suitability must be obtained from Megger. Refer to the warranty information
included at the end of this instruction manual. Specifications are subject to change
without notice.
WARRANTY
Products supplied by Megger are warranted against defects in material and
workmanship for a period of one year following shipment. Our liability is
specifically limited to replacing or repairing, at our option, defective equipment.
Equipment returned to the factory must be shipped prepaid and insured. This
warranty does not include batteries, lamps, or other expendable items, where the
original manufacturer's warranty shall apply. We make no other warranty. The
warranty is void in the event of abuse (failure to follow recommended operating
procedures) or failure by the customer to perform specific maintenance as
indicated in this manual.

AVTMTTR25 Rev C April 2008 i
TABLE OF CONTENTS
1INTRODUCTION......................................................................................................................... 1
About the TTR25........................................................................................................1
Electrical Theory and Practice ...................................................................................2
Applications for the TTR25 ........................................................................................4
Upon Receipt of the TTR25.......................................................................................5
Safety First.................................................................................................................5
How to Use This Manual............................................................................................5
2SAFETY ................................................................................................................................... 7
Overview....................................................................................................................7
Safety Requirements .................................................................................................7
Cautions and Warnings..............................................................................................8
3CONTROLS &CONNECTORS...................................................................................................... 9
Overview....................................................................................................................9
Connectors ..............................................................................................................10
4SETUP,CONNECTIONS AND OPERATION.................................................................................. 11
General Instructions.................................................................................................11
Transformers ...........................................................................................................11
Single-Phase, Two-Winding Transformers ..............................................................12
Distribution Transformers with Two Secondary Windings........................................12
Three-Phase, Two-Winding Transformers...............................................................16
Three-Phase, Three-Winding Transformers ............................................................16
Current Transformers (CTs).....................................................................................17
General Operating Procedure..................................................................................20
Description of Menus and Test Screens..................................................................20
Use with the Optional Printer ...................................................................................23
HyperTerminal Configuration...................................................................................25
5MAINTENANCE AND TROUBLESHOOTING.................................................................................... 27
Maintenance ............................................................................................................27
Calibration Check.....................................................................................................27

AVTMTTR25 Rev C April 2008
ii
TTR25 Functional Test ............................................................................................28
Battery Replacement ...............................................................................................29
Troubleshooting.......................................................................................................30
Error Messages........................................................................................................31
Repair......................................................................................................................33
APPENDIX A-SPECIFICATIONS.................................................................................................... 35
Electrical ..................................................................................................................35
Environmental Conditions........................................................................................37
Physical Data...........................................................................................................37
Optional Accessories...............................................................................................38
APPENDIX B-ORDERING INFORMATION &SPARE PARTS LIST ....................................................... 39
APPENDIX C-CONNECTIONS AND VECTOR VOLTAGE DIAGRAMS ................................................... 41

AVTMTTR25 Rev C April 2008 iii
LIST OF ILLUSTRATIONS
Figure 1-1. TTR25 Single-Phase Test Set Block Diagram ..................................................... 4
Figure 3-1 TTR25 Display & Control Panel ........................................................................... 9
Figure 3-2 TTR25 Top Side Connector Panel..................................................................... 10
Figure 4-1 Setup for Testing Single-Phase Transformer..................................................... 13
Figure 4-2 Setup for Testing Single-Phase Autotransformer............................................... 13
Figure 4-3 Setup for Testing Single-Phase, Type A Step Voltage Regulator ...................... 14
Figure 4-4 Setup for Testing Single-Phase, Type B Step Voltage Regulator ...................... 14
Figure 4-5 Setup for Testing X1 – X2 Winding of Distribution Transformer......................... 15
Figure 4-6 Setup for Testing X3 – X2 Winding of Distribution Transformer......................... 15
Figure 4-7 Setup for Testing X1 – X3 Winding of Distribution Transformer......................... 15
Figure 4-8 Setup for Testing Unmounted Current Transformer........................................... 18
Figure 4-9 Setup for Testing Taps on Multiple Tap CT........................................................ 18
Figure 4-10 Setup for Testing BCT Mounted on Single-Phase Two-Winding Transformer ... 19
Figure 4-11 TTR25 Opening Display Screen......................................................................... 20
Figure 4-12 Start Test Screen............................................................................................... 21
Figure 4-13 Test in Progress Screen..................................................................................... 22
Figure 4-14 TTR25 Test Result Screen................................................................................. 22
Figure 4-15 Sample Test Report........................................................................................... 23
Figure 4-16 Printer Configuration Printout............................................................................. 24

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iv
LIST OF TABLES
TABLE 5-1 TROUBLESHOOTING GUIDE...................................................................................... 30
TABLE 5-2 SELF-TEST ERROR MESSAGES ................................................................................ 31
TABLE 5-3 TEST ERROR MESSAGES......................................................................................... 31
TABLE 5-4 MISCELLANEOUS MESSAGE ..................................................................................... 32
TABLE C-1 ANSI TRANSFORMER WINDING PHASE RELATIONSHIP .............................................. 42
TABLE C-2 ANSI TRANSFORMER WINDING PHASE RELATIONSHIP .............................................. 44
TABLE C-3 CEI/IEC 76-1:1993 TRANSFORMER WINDING PHASE RELATIONSHIP......................... 54
TABLE C-4 TRANSFORMER WINDING PHASE RELATIONSHIP (AUSTRALIAN STD.2374, PART 4-1982)
................................................................................................................................................ 64

AVTMTTR25 Rev C April 2008 1
1
INTRODUCTION
About the TTR25
The TTR25 Handheld TTR®Test Set is a fully automatic, self-checking, self-
calibrating unit. The test set measures the turn ratio, excitation current, and
phase displacement (polarity) of single- and three-phase (phase by phase)
distribution transformers, as well as power, potential and current transformers.
The TTR25 Handheld TTR®Test Set is powered by six AA-size replaceable
alkaline batteries. The test set is a portable instrument housed in a sturdy plastic
case. A carrying case with strap and an accessory pouch is provided with the test
set.
The test set can be used to test single-phase and three-phase transformers, both
with and without taps in accordance with the requirements of the IEEE C57.12.90
– 1997 standards. For three-phase transformers, the test set is connected to
each of the three phases of the transformer to be tested, and measurements are
made on a phase by phase basis.
Turn ratio, phase displacement (polarity), and excitation current are displayed on
a large LCD. Transformer excitation current helps to detect transformer shorted
turns or an unequal number of turns connected in parallel. Operating condition
(error) messages identify incorrect test connections, abnormal operating
condition, or winding problems. Test results can be printed out on an optional
printer.
Features include:
Fully automatic operation.
Self-checking at power-up.
Self-calibration at each measurement.
User-friendly, one button operation.
Test turn ratio, excitation current, and phase displacement (polarity).

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Easy measuring of single and three phase (phase by phase) transformers, as
well as potential & current transformers.
Checking reverse test lead or winding connections at start of each test.
External optional printer records test data.
Three automatically selected excitation test voltages: 8 V, 1.5 V, and 0.5 V.
Testing to ANSI, IEC and Australian standards.
Leads marked to ANSI, IEC and Australian standards.
Choice of seven languages
Large, easy-to-read LCD shows alphanumeric data
Meets the requirements of both the European EMC and Low Voltage Directives
(CE mark).
Trouble-free operation in switchyards under electrostatic and magnetic
interference conditions.
Electrical Theory and Practice
How the TTR25 Works
The TTR25 test set provides the excitation voltage to the input of the transformer.
It accurately measures both the H-side and X-side voltages to calculate turns
ratio. The TTR also measures phase displacement (polarity) between primary
and secondary windings of a transformer, and transformer excitation current.
Transformer Turns Ratio
Transformer Turns Ratio is the ratio of the number of turns in the high voltage
winding to that in the low voltage winding. Transformer ratio can change due to
several factors, including physical damage from faults, deteriorated insulation,
contamination and shipping damage.
A Transformer Turns Ratio Test Set such as the TTR25 can directly measure the
turns ratio of single-phase transformers as well as three-phase transformers.
Deviations in these measurements will quickly indicate problems in transformer
windings and in the magnetic core circuits. If a transformer ratio deviates more
than 0.5 percent from the rated voltage ratio, it may not operate reliably. To
measure small ratio changes such as this, the accuracy of a Megger TTR25 is
needed.
Excitation Current
The TTR25 is capable of measuring exciting current by applying voltage to one of
the transformer’s windings. An accurate measurement of exciting current can

INTRODUCTION
AVTMTTR25 Rev C April 2008 3
provide information about the condition of a transformer’s core. Unwanted
circulating currents, unintentional grounds or even an incipient short circuit can
affect the exciting current and indicate a problem.
Transformer Polarity
Polarity of a distribution transformer becomes of interest in order to determine its
proper connection within a power network. The Megger TTR25 will identify
normal (in phase) and reverse polarity of the single-phase transformers.
A block diagram of TTR25 is shown in Figure 1-1. The excitation voltage
oscillator applies a 55-Hz test voltage to a transformer under test. There are
three test voltages: 0.5 V, 1.5 V, and 8 V used for transformer testing. Test
voltage selection is based on excitation current required. The required test
voltage is selected automatically.
Input and output transformer voltages are applied to conditioning circuitry. This
circuitry improves signal-to-noise ratio of the test signal, and provides full voltage
range of the test signals at A/D converter inputs.
A/D converter is used to convert the analog measurement signals to their digital
replica. The converted output digital signals are applied to CPLD (complex
programmable logic device) and then are transferred to microprocessor.
The microprocessor is the main part of the TTR test set. It provides proper timing
sequence of operation, gathers and calculates the test result, and interfaces with
peripherals. There are three main peripherals in the TTR25 test set:
RS-232/Printer port, LCD and keypad.
DC power supply converts the primary battery voltage, six Energizer®X91 AA-
alkaline batteries, 9 V (nominal), 3135 mAh nominal capacity, into the secondary
DC voltages required for proper operation of the TTR25 test set.

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Figure 1-1.TTR25 Test Set Block Diagram
Applications for the TTR25
The proper operation of a transformer relies almost entirely on the electrical
properties of its windings. To ensure continued proper operation, transformers
are tested to verify that their electrical properties have not changed from design
specifications. A TTR is an extremely useful instrument for testing transformer
windings because it can help locate several types of problems within single- and
three-phase transformers.
It is used to determine the no-load accuracy of CTs and PTs and also determine
the need to further test faulty CTs and PTs.
The TTR25 applies voltage to the high-voltage winding of a transformer and
accurately measures the resulting voltage from the low voltage winding. The ratio
of voltages is directly proportional to turns ratio. In addition, the unit measures
excitation current and polarity.
MICROPROCESSOR CPLD
Exc. Voltage
Oscillator
Transforme
r
Under Test Input/Output
Signal
Conditioning
Circuitry
A/D
Converter
RS232/Printe
r
Port 128 x 64 LCD Keypad DC Powe
r
Supply

INTRODUCTION
AVTMTTR25 Rev C April 2008 5
Upon Receipt of the TTR25
Check the equipment received against the packing list to ensure that all materials
are present. Notify Megger of any shortage. Telephone [phone].
Examine the instrument for damage received in transit. If any damage is
discovered, file a claim with the carrier at once and notify Megger or its nearest
authorized sales representative, giving a detailed description of the damage.
This instrument has been thoroughly tested and inspected to meet rigid
specifications before being shipped. It is ready for use when set up as indicated
in this manual.
Safety First
Be sure to read the safety information in Chapter 2 thoroughly and observe all
safety precautions and recommendations.
How to Use This Manual
Typographic Conventions
GCAUTION
Cautions alert you to possible damage to equipment.
F WARNING
Warnings alert you to conditions that are potentially
hazardous to people.
NOTE: Notes provide important information.

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2
SAFETY
Overview
The TTR25 must be used on de-energized transformers. However, the
transformer to which the test set is connected is a possible source of high-
voltage electrical energy and all persons making or assisting in tests must use all
practical safety precautions to prevent contact with potentially energized parts of
the transformer and related circuits. Persons actually engaged in the test must
stand clear of all parts of the complete high-voltage circuit, including all
connections, unless the test set is de-energized and all parts of the test circuit
are grounded. Persons not directly involved with the work must be kept away
from test activities by suitable barriers, barricades, or warnings.
Treat all terminals of high-voltage power equipment as a potential electric shock
hazard. There is always the possibility of voltages being induced at these
terminals because of proximity to energized high-voltage lines or equipment.
Always disconnect test leads from power equipment before attempting to
disconnect them at the test set. The ground connection must be the first made
and the last removed. Any interruption of the grounding connection can create an
electric shock hazard.
Any repair or component replacement must be performed by qualified service
personnel.
Safety Requirements
Megger has made formal safety reviews of the initial design and any subsequent
changes. This procedure is followed for all new products and covers areas in
addition to those included in applicable standards. Regardless of these efforts, it
is not possible to eliminate all hazards from electrical test equipment. For this
reason, every effort has been made to point out in this instruction manual the
proper procedures and precautions to be followed by the user in operating this
equipment and to mark the equipment itself with precautionary warnings where
appropriate. It is not possible to foresee every hazard that may occur in the
various applications of this equipment. It is therefore essential that the user, in

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addition to following the safety rules in this manual, also carefully consider all
safety aspects of the test before proceeding.
Safety is the responsibility of the user.
Follow your company safety procedures.
Misuse of this equipment can be extremely dangerous.
The purpose of this equipment is limited to use as described in this manual. Do
not use the equipment or its accessories with any device other than specifically
described.
Never connect the test set to energized equipment.
Do not use the test set in an explosive atmosphere.
Corrective maintenance must only be performed by qualified personnel who are
familiar with the construction and operation of the test set and the hazards
involved.
Refer to IEEE 510 - 1983, IEEE Recommended Practices for Safety in High-
Voltage and High-Power Testing, for additional information.
If the test equipment is operated properly and all grounds correctly made, test
personnel need not wear rubber gloves. As a routine safety procedure, however,
some users require that rubber gloves be worn, not only when making
connections to the high-voltage terminals, but also when manipulating the
controls. Megger considers this an excellent safety practice.
Users of equipment should note that high-voltage discharges and other sources
of strong electric or magnetic field may interfere with the proper functioning of
heart pacemakers. Persons with heart pacemakers should obtain expert advice
on the possible risks before operating this equipment or being close to the
equipment during operation.
Cautions and Warnings
Warning and caution notices are used throughout this manual where applicable
and should be strictly observed.

AVTMTTR25 Rev C April 2008 9
3
CONTROLS & CONNECTORS
Overview
The TTR25 is a simple, push-to-test instrument with few buttons and controls. It
has no menus except for a print button and language selection.
Contrast This knob adjusts the viewing resolution of the screen.
Backlight A momentary depression of the switch will either activate or
de-activate the backlight. It will remain ON for a period of
three minutes without activity.
Power ON Switch Press this switch to turn the TTR25 on.
Power OFF Switch Press this switch to turn the TTR25 off.
DISPLAY SCREEN LCD displays menus and test information.
KEYPAD 4-button keypad for entering menu selections and
navigating through the various screens.
Figure 3-1 TTR25 Display & Control Panel
Contrast
Display Screen
Power ON switch
Back Light switch Power OFF switch
Keypad

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Connectors
Figure 3-2 TTR25 Top Side Connector Panel
TEST CABLE Plug receptacle for connecting test leads to the
high-voltage (H) and low-voltage (X) windings of a
transformer. The plug and receptacle are keyed
to prevent the cable from being inserted
incorrectly, and to make certain that the correct
cable is used.
RS-232/PRINTER A DB-9 male connector for connecting a printer or
to upload data in real time to a PC (using
HyperTerminal).
TEST CABLE
PRINTER

AVTMTTR25 Rev C April 2008 11
4
SETUP, CONNECTIONS AND OPERATION
General Instructions
When testing high-voltage transformers, caution must be used at all times and all
safety precautions followed. Read and understand all safety information
contained in Section 2, Safety.
F
WARNING
Ensure that the transformer to be tested is completely de-energized.
Check every winding. Ensure that all terminals of the transformer are
disconnected from line or load at the transformer. For some
transformers, connections to ground may be left in place.
Never interchange connections between the high- and low-voltage
transformer terminals. Failure to observe proper connections will result
in a safety hazard and may result in damage to the test set or
transformer.
Check that a lead set connected is labeled for TTR25 test set operation.
The TTR25 has been designed to test a variety of transformers, such as: Single
phase, Three phase (one phase at a time), CTs, PTs and Voltage Regulators.
Do not leave the TTR25 test set exposed below -20 0C or above 55 0C for more
than 2 hours. Such conditions will lead to shortened service life of batteries.
When storing the TTR25 at temperatures below -20 0C or above 55 0C, remove
the batteries. See Battery Replacement for detail.
Transformers
The setup and connection instructions pertaining to ratio, polarity, and phase
relation assume that the transformer under test, connections, and terminal
markings comply with the requirements of ANSI C57.12.70-1978 American
National Standards Terminal Markings and Connections for Distribution and
Power Transformers. The H leads of the test cable are the exciting leads.

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The TTR25 may supply up to 100 mA of excitation current. The TTR25 will
automatically select the appropriate test voltage (8 V, 1.5 V, or 0.5 V) when
testing transformers.
Single-Phase, Two-Winding Transformers
Perform the following setup procedure for single-phase, two-winding
transformers:
1. Connect the test lead set to the TEST CABLE receptacle of the TTR25
test set. Make sure that the connector is fully engaged into the receptacle.
2. Connect the clips marked H1 and H2 of the test lead to the corresponding
(high-voltage winding) terminals of the transformer under test.
3. Connect the clips marked X1, X2 of the test lead to the corresponding
(low-voltage winding) terminals of the transformer under test. Figures 4-1
and 4-2 show test setups for single-phase transformers. Figures 4-3 and
4-4 show test setups for voltage regulators.
NOTE: When properly connected, expect that polarity of the windings is
normal (“+” sign is displayed in front of the turns ratio test
result).
If the sign is "-", then check the lead connections.
Distribution Transformers with Two Secondary Windings
The TTR25 may test the turn ratios of distribution transformer secondary
windings (one at a time). Perform the following setup procedure for single-phase
distribution transformer with two secondary windings:
1. Connect the test lead set to the TEST CABLE receptacle of the TTR25
test set. Make sure that the connector is fully engaged into the receptacle.
2. Connect the clips marked H1 and H2 of the test lead to the corresponding
(high-voltage winding) terminals of the transformer under test.
3. When testing X1-X2 winding, connect, respectively, the clips marked X1
and X2 of the test lead to the X1 and X2 terminals of the transformer
under test. Expect that polarity of the windings is normal (“+” sign is
displayed in front of the turns ratio test result). ). See Figure 4-5.
4. When testing X3-X2 winding, connect the X1 clip to X3 transformer
terminal, and connect the X2 clip to X2 transformer terminal. Expect that