Vanguard Instruments TRM-20 User manual

TRM-20 and TRM-40
TRANSFORMER RESISTANCE METERS
USER’S MANUAL
Vanguard Instruments Company, Inc.
1520 S. Hellman Ave.
Ontario, California 91761, USA
TEL: [phone]
FAX: [phone]
August 2017
Revision 1.5

TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
i
SAFETY SUMMARY
NOTICE
This manual applies to both the TRM-20 and TRM-40 transformer resistance meters. The
operating procedures are virtually the same for both models, and any differences are clearly
described where applicable.
FOLLOW EXACT OPERATING PROCEDURES
Any deviation from the procedures described in this User’s Manual may create one or more
safety hazards, may damage the TRM-20/40, damage the test transformer, or cause errors in
the test results. Vanguard Instruments Company, Inc. assumes no liability for unsafe or
improper use of the TRM-20/40.
All safety precautions provided in this manual must be observed during all phases of testing
including test preparation, test lead connection, actual testing, and test lead disconnection.
SAFETY WARNING AND CAUTIONS
The TRM-20/40 shall be used only by trained operators. All transformers under test shall be
off-line and fully isolated.
DO NOT MODIFY TEST EQUIPMENT
To avoid the risk of introducing additional or unknown hazards, do not install substitute parts or
perform any unauthorized modification to any TRM-20/40 test unit. To ensure that all designed
safety features are maintained, it is highly recommended that repairs be performed only by
Vanguard Instruments Company factory personnel or by an authorized repair service provider.
Unauthorized modifications can cause safety hazards and will void the manufacturer’s
warranty.
WARNING
Do not remove test leads during a test. Failure to heed this warning can result in electrical
shock to personnel and damage to the equipment.

REV 1.5 TRM-20 AND TRM-40 USER’S MANUAL
ii
TABLE OF CONTENTS
CONVENTIONS USED IN THIS DOCUMENT ....................................................................... 1
1.0 INTRODUCTION .................................................................................................................... 2
1.1 General Description and Features ................................................................................... 2
1.2 Technical Specifications ................................................................................................... 4
1.3 TRM Controls and Indicators ........................................................................................... 5
2.0 PRE-TEST SETUP ................................................................................................................... 6
2.1 Operating Voltages .......................................................................................................... 6
2.2 LCD Screen Contrast Control ............................................................................................ 6
2.3 Printer Paper Control ....................................................................................................... 6
2.4 Printer Paper .................................................................................................................... 6
2.5 Replacing the Thermal Printer Paper ............................................................................... 7
3.0 OPERATING PROCEDURES ................................................................................................... 8
3.1 Configuring the LTCA Software for use with the TRM ..................................................... 8
3.2 Connecting the TRM to a PC via Bluetooth ................................................................... 10
3.3 Typical Connections to a Load Tap Changer (LTC) ......................................................... 17
3.4 Typical TRM-20/40 Cable Connections .......................................................................... 17
3.5 General Procedures ....................................................................................................... 19
3.6 Entering Test Record Header Information ..................................................................... 20
3.7 Setting the Date and Time ............................................................................................. 23
3.8 Setting the Interface Language ...................................................................................... 24
3.9 Performing a Resistance Test ......................................................................................... 25
3.10 Performing a Load Tap Changer / Voltage Regulator Resistance Test .......................... 34
3.11 Performing a Special Resistance Test ............................................................................ 43
3.12 Performing a Dynamic LTC Test ..................................................................................... 50
3.13 Performing a Diagnostic Test ......................................................................................... 55
3.14 Demagnetizing the Transformer Core ........................................................................... 57
3.15 Working with Test Records ............................................................................................ 59
3.15.1. Viewing the Contents of the Working Memory ..................................................... 59
3.15.2. Saving Test Results to a Test Record ...................................................................... 61
3.15.3. Restoring a Test Record From Flash EEPROM ........................................................ 63
3.15.4. Restoring a Test Record From a USB Flash Drive ................................................... 67
3.15.5. Copying Test Records to a USB Flash Drive ............................................................ 69
3.15.6. Printing a Test Record Directory ............................................................................ 72
3.15.7. Erasing Test Records from the Flash EEPROM ....................................................... 74
3.16 Erasing Test Records from a USB Flash Drive ................................................................ 77
3.17 Converting Resistance Measurements .......................................................................... 80

TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
iii
LIST OF FIGURES
Figure 1. TRM-20/40 Controls and Indicators ................................................................................ 5
Figure 2. Typical Connections to a Load Tap Changer (LTC) ......................................................... 17
Figure 3. Typical TRM Connections Diagram for A Dynamic Resistance Test .............................. 17
Figure 4. Typical Single Phase TRM Connections .......................................................................... 18
Figure 5. Typical TRM Connections Diagram for 2 Windings ........................................................ 18
Figure 6. Typical Resistance Test Results Printout........................................................................ 33
Figure 7. Typical LTC/Voltage Regulator Test Report Printout ..................................................... 42
Figure 8. Typical Special Test Report Printout .............................................................................. 49
Figure 9. Typical Dynamic LTC Test Results Printout Showing an Opened Circuit ....................... 54
Figure 10. Typical Test Record Directory Printout ........................................................................ 73
LIST OF TABLES
Table 1. TRM-20/40 Technical Specifications ................................................................................. 4

REV 1.5
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TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
2
1.0 INTRODUCTION
1.1 General Description and Features
The TRM-20 and TRM-40 are Vanguard Instruments’ third generation transformer winding
resistance meters. The TRM line is designed specifically to measure DC resistance values of
transformer windings, rotating machine windings, or any dc resistance of an inductive device.
The TRM line features dual resistance-reading input channels that can measure two winding
resistances simultaneously (primary and secondary windings of a transformer).
Both the TRM-20 and TRM-40 can provide a fast and stable reading of very large transformers
by utilizing a 60Vdc power supply. The TRM-20 is capable of outputting a selectable test current
from 1A to 20A while the TRM-40’s test current is selectable from 1A to 40A.
Since the TRM-20 and TRM-40 can accurately measure resistance values from 1 micro-ohm to
2,000 Ohms, they can be used as micro-ohm meters to measure EHV circuit breaker contact
resistance, or for any low resistance measuring application.
If the transformer winding resistance temperature is available at the time of testing, the TRM
can calculate the equivalent resistance value at any temperature value. This useful feature
allows the user to compare the field readings against the factory test resistance values.
A special test mode allows the TRM to collect data automatically for up to 90minutes (at 60-
second sampling interval) or 45 minutes (at 30 second sampling interval). Test data is recorded
with a time stamp.
All test results can be printed on a 2.5” wide thermal printer. Test record header information
including the company, substation name, transformer information can also be entered using
the 16-key key pad.
The TRM-20 and TRM-40 can also demagnetize the inductive device under test, eliminating the
manual task of demagnetizing the transformer core after a resistance test.
The TRM also has a “make-before-break” test mode that can be used to test the load tap
changer (LTC) or voltage regulator test sequence. The TRM produces a “Dynamic-Resistance”
graph of the LTC or voltage regulator contact under operation. An opened contact can be
detected visually from this resistance chart.
The TRM’s built-in LTC/Voltage regulator can be used to change the LTC/Voltage regulator tap
position from the TRM front panel.
Safety Features
The TRM automatically dissipates the energy stored in the transformer at the end of each test.
The discharge circuit will continue to work even if the TRM power supply is lost.
Test Record Storage
The TRM can store up to 100 test records internally. For external test record storage, the TRM
features a USB Flash drive interface port. Up to 999 test records can be stored on a connected
USB Flash drive.

REV 1.5 TRM-20 AND TRM-40 USER’S MANUAL
3
User Interface
The TRM features a back-lit graphic LCD screen (124x64) that is clearly viewable in both bright
sunlight and low-light levels. An alpha-numeric keypad is used to enter test information and to
operate the unit.
Computer Interfaces
The TRM can be connected to a PC via the unit’s RS-232C, USB, or Bluetooth interface. A PC can
be used to retrieve test records (stored in the TRM or USB Flash drive) or to run tests using the
provided software. Test records are automatically exported to PDF, Excel, and XML formats.

1.2
T
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YSICAL SPE
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OPERATI
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RESISTAN
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TYPE
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RANGE
ACCURACY
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T CURRENT
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T VOLTAGE
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CHANNEL
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DISPLAY
PRINTER
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ST RECORD
STORAGE
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ST RECORD
STORAGE
N
TERFACE
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SAFETY
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VIRONMENT
M
IDITY (MAX)
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TUDE (MAX)
CABLES
OPTIONS
WARRANTY
a
bove specif
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1. TRM-20/4
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21” W x 17”
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1 micro-ohm
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REV 1.5 TRM-20 AND TRM-40 USER’S MANUAL
5
1.3 TRM Controls and Indicators
The TRM-20/40’s controls and indicators are shown in Figure 1. The purpose of the controls and
indicators may seem obvious, but users should become familiar with them before using the
TRM. Accidental misuse of the controls will usually cause no serious harm. Users should also be
familiar with the safety summary found on the front page of this User’s Manual.
Figure 1. TRM-20/40 Controls and Indicators

TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
6
2.0 PRE-TEST SETUP
2.1 Operating Voltages
The TRM’s operating voltages are 90-240 Vac, 50/60 Hz.
2.2 LCD Screen Contrast Control
To increase the LCD screen contrast, press and hold the [] key for two seconds.
To decrease the LCD screen contrast, press and hold the [] key for two seconds.
2.3 Printer Paper Control
To advance the TRM printer paper, press and release the [] key.
To retract the TRM printer paper, press and release the [] key.
2.4 Printer Paper
The TRM’s built-in thermal printer uses 2.5-inch wide thermal paper for printing test results. To
maintain the highest print quality and to avoid paper jams, the use of thermal paper supplied
by Vanguard Instruments Company is highly recommended. Additional paper can be ordered
from the following sources:
Vanguard Instruments Co, Inc.
1520 S. Hellman Avenue
Ontario, CA 91761
Tel: [phone]
Fax: [phone]
Part Number: VIC TP-3 paper
BG Instrument Co.
13607 E. Trent Avenue
Spokane, WA 99216
Tel: [phone]
Fax: [phone]
Part Number: VIC TP-3 paper

REV 1.5
7
2.5
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TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
8
3.0 OPERATING PROCEDURES
3.1 Configuring the LTCA Software for use with the TRM
The TRM can be used with a PC using the Vanguard LTCA software. Follow the steps below to
properly connect the TRM and configure the LTCA application to recognize the unit.
a. Install the LTCA software (please see the LTCA software user’s manual for details).
b. Connect the TRM to the PC by connecting a USB cable from an open USB port on the PC
to the unit’s “USB PC” port.
c. Turn on the power on the TRM.
d. If this is the first time you are connecting the unit to the PC, Windows will recognize it as
a new device and automatically install necessary drivers. If using Windows XP, you may
be prompted to install drivers. Select the automatic installation option and Windows will
locate the generic drivers necessary.
e. Please note that although the unit is connected via USB, it uses an internal serial
interface to communicate with the PC. As such, it will appear in the windows Device
Manager as a USB Serial Port. Open the Device Manager from the Windows Control
Panel and note the COM port number. For example, in the installation shown below, the
TRM is shown as COM10 (USB Serial Port).

REV 1.5 TRM-20 AND TRM-40 USER’S MANUAL
9
f. Launch the LTCA application and then click on the “Settings” icon. The following window
will be displayed:
Make sure the “Use USB Port” option is UN-checked. Then, from the “COM Port” drop-
down menu, select the COM port that corresponds to the port that the TRM is
connected to. Then click the OK button. The LTCA software will now recognize the TRM.

TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
10
3.2 Connecting the TRM to a PC via Bluetooth
The TRM can also be connected wirelessly to a PC using Bluetooth. To connect the unit via
Bluetooth, it must first be paired with the PC. Follow the steps below to pair the TRM to a PC
via Bluetooth:
For Windows XP:
a. Make sure the TRM is turned on. Then double click on the Bluetooth system tray icon
(on the bottom right corner of your computer screen):
b. The “My Bluetooth Places” window will be displayed:
Click on “Add a Bluetooth Device” on the left window pane.
c. The Bluetooth Setup Wizard window will be displayed. Click on the “Next” button. The
PC will scan for nearby devices and list all available Bluetooth devices:

REV 1.5 TRM-20 AND TRM-40 USER’S MANUAL
11
The TRM will be listed as “TRM S/N” where S/N is the device’s serial number. Click on
the icon for the TRM and then click on the “Next” button.
d. The following window will be displayed asking for a secret key to connect to the TRM:
Type the word “default” (without the quotes and in all lower-case) and then click on the
“Next” button.
e. The following window will be displayed with the option to connect to the TRM as a serial
port:
Make sure to check the box next to “AT Serial” and then click on the “Next” button.

TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
12
f. The following confirmation screen will be displayed:
Click on the “Finish” button.
g. The TRM-20 will now be displayed in the “My Bluetooth Places” window:
Note the port number listed under the device name. In the above case, the port number
is COM14. Use this port number in the LTCA software to connect to the TRM.

REV 1.5 TRM-20 AND TRM-40 USER’S MANUAL
13
For Windows 7:
a. Make sure the TRM is turned on. Then double click on the Bluetooth system tray icon
(on the bottom right corner of your computer screen):
b. The “Bluetooth Devices” window will be displayed:
Click on “Add a device”.

TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
14
c. All nearby Bluetooth devices will be listed:
The TRM will be listed as “TRM S/N” where S/N is the device’s serial number. Click on
the icon for the TRM and then click on the “Next” button.
d. The device pairing screen will be displayed:
Click on “Enter the device’s pairing code” option.

REV 1.5 TRM-20 AND TRM-40 USER’S MANUAL
15
e. The following window will be displayed:
Type the word “default” (without the quotes and in all lower-case) in the text box and
click on the “Next” button.
f. The following screen will be displayed:
Click on the “Close” button.

TRM-20 AND TRM-40 USER’S MANUAL REV 1.5
16
g. The TRM will now be listed under “Bluetooth Devices”:
Right click on the TRM-20 icon and select “Properties” from the pop-up menu.
h. The properties window will be displayed. Click on the “Hardware” tab:
Note the port number listed after the device name (COM23 in the above example). Use this
port number in the LTCA software to connect to the TRM.