RMO-TW
WINDING OHMMETERS
Manual
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RMO-TW
Contents
Contents
1.
Introduction ............................................................................................................................................................. 3
1.1
Safety Instructions ............................................................................................................................................ 3
1.1.1
Safety Terms and Symbols ....................................................................................................................... 3
1.1.2
Terms of Use ............................................................................................................................................ 3
1.1.3
Orderly Practices and Procedures ............................................................................................................ 4
1.1.4
Device Maintenance ................................................................................................................................. 4
1.1.5
Operator Qualifications ............................................................................................................................. 4
1.1.6
Safe Operating Procedures ...................................................................................................................... 4
1.2
Power Supply .................................................................................................................................................... 5
1.3
Measurement Category .................................................................................................................................... 5
1.4
Intended Use ..................................................................................................................................................... 6
2
Description ............................................................................................................................................................... 7
2.1
Front and Rear Panel Components .................................................................................................................. 7
3
Testing.................................................................................................................................................................... 10
3.1
Connecting the RMO-TW to a Test Object ..................................................................................................... 10
3.2
The Current Test ............................................................................................................................................. 11
3.2.1
Setting the Measurement Parameters .................................................................................................... 11
3.2.2
The Measurement Process ..................................................................................................................... 11
3.2.3
Viewing the Test Results ........................................................................................................................ 13
3.3
The Tap Changer Test .................................................................................................................................... 13
3.3.1
Setting the Measurement Parameters .................................................................................................... 14
3.3.2
Tap Changer Test with the RMO-TW ..................................................................................................... 15
3.4
Measurement Parameters .............................................................................................................................. 17
4
Error Messages ...................................................................................................................................................... 18
4.1
Error Message "Open Connection" ................................................................................................................. 18
4.2
Error Messages "Connection CH1-2-3" and "Connection CH1" ..................................................................... 18
4.3
Error Message "Polarity" ................................................................................................................................. 19
4.4
Error Messages "Change Current" and “Overcurrent” .................................................................................... 19
4.5
Error Message "Overheat" .............................................................................................................................. 19
4.6
Error Message "Mains Voltage < 90V" ........................................................................................................... 20
4.7
Error Messages "Error Printer" and "Check Paper" ........................................................................................ 20
5
Troubleshooting ..................................................................................................................................................... 21
5.1
Accuracy Check .............................................................................................................................................. 21
5.2
Open Circuit Voltage Check ........................................................................................................................... 21
5.3
Test Currents Check ....................................................................................................................................... 22
5.4
Voltage Measurement Check ......................................................................................................................... 23
5.5
TestCom Diagnostic Software ........................................................................................................................ 23
6
Customer Service ................................................................................................................................................... 24
7.
Packing the Instrument for Shipment ..................................................................................................................... 24
8
Technical Data ....................................................................................................................................................... 25
8.1
Mains Power Supply ....................................................................................................................................... 25
8.2
Output Data ..................................................................................................................................................... 25
8.3
Measurement .................................................................................................................................................. 25
8.4
Environmental Conditions ............................................................................................................................... 25
8.5
Dimensions and Weight .................................................................................................................................. 26
8.6
Applicable Standards ...................................................................................................................................... 26
9
Instrument & Accessories ...................................................................................................................................... 27
Manufacturer Contact Information .................................................................................................................................. 28
Manual Version: M-RXX0TW-201-U-EN
This Manual refers to the firmware version 11.00
Refers to:
RMO10TW, RMO20TW, RMO30TW and RMO50TW models
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RMO-TW
Introduction
1. Introduction
The purpose of this Manual is to provide helpful instructions on how to use the RMO-TW instruments safely,
properly and efficiently.
The following instructions will help the user avoid unsafe situations, reduce maintenance costs and will ensure
the reliability and durability of the RMO-TW instruments.
The RMO-TW must be used in observance of all existing safety requirements and regulations based on
national/local standards for accident prevention and environmental protection. In addition, the relevant
international standards are listed in paragraph 8.6 of the “Technical data” section of this document.
1.1
Safety Instructions
Safety is the responsibility of the user. Before operating the RMO-TW, please read the following safety
instructions carefully.
It is not recommended that the RMO-TW is used (or even turned on) without careful observation of the
instructions listed in this Manual. The RMO-TW should only be operated by trained and authorized personnel.
1.1.1 Safety Terms and Symbols
Terms in this Manual. The following terms may appear in this manual:
WARNING: Warning statements identify conditions or practices that could result in injury or loss of life.
CAUTION: Caution statements identify conditions or practices that could result in damage to this product or to
other property.
Terms on the Device. The following warning terms used in this document may appear on the device:
WARNING: indicates that potential hazard may occur.
CAUTION: indicates that potential damage may occur to the instrument or to the test object connected to the
instrument.
Symbols on the Product. The following symbols may appear on the device:
Refer to
Manual
Protective
Earth
Terminal
1.1.2 Terms of Use
•
•
•
•
The RMO-TW shall be used only if it is in good technical condition. Its use shall be in accordance with
local safety and industrial regulations. Adequate precautions must be taken to avoid any risks related to
high voltages associated with this equipment and nearby objects.
The RMO-TW shall be used only for the application purposes specified in the ”Intended Use” section of
this Manual. The manufacturer and distributors are not liable for any damage resulting from wrong
usage. The user bears responsibility in case of not following the instructions defined in this document.
Do not remove the protective casing of the RMO-TW.
All service and maintenance work must be performed by qualified personnel only.
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Introduction
1.1.3 Orderly Practices and Procedures
•
•
•
•
•
The Manual shall always be available on the site where the RMO-TW is used.
Before using the RMO-TW, all personnel (even personnel who only occasionally, or less frequently,
work with the RMO-TW) assigned to operate the RMO-TW should read this Manual.
Do not make any modifications, extensions, or adaptations to the RMO-TW.
Use the RMO-TW only with the original accessories provided by its manufacturer.
Use the RMO-TW and its original accessories for the device's intended use only.
1.1.4 Device Maintenance
This device should be kept clean in order to prevent excessive cases of dust or other contaminants affecting its
operation. It should be cleaned with water/isopropyl alcohol after any dirt/contaminants are noticed on its
surfaces.
1.1.5 Operator Qualifications
•
•
Testing with the RMO-TW should only be carried out by authorized and qualified personnel.
Personnel receiving training, instruction or education on the RMO-TW should remain under the constant
supervision of an experienced operator while working with the test set and the test object.
1.1.6 Safe Operating Procedures
•
•
•
•
•
•
•
•
•
•
•
•
Hazardous voltages of up to 400 V can occur inside the RMO-TW. Therefore, it is not permitted to remove
the protective casing of the RMO-TW.
Hazardous voltages exist on the terminals of the RMO-TW when the red LED is lit. Never assume that the
connections are safe even if this LED is off. Switch off and unplug the RMO-TW before touching the
connections, particularly if a fault is suspected.
Before putting the RMO-TW into operation, check the test set for any visible damage.
Cables between the RMO-TW and other equipment shall be connected and disconnected from the RMOTW only while the instrument is switched off.
Do not operate the RMO-TW under wet or moist conditions (condensation).
Do not operate the RMO-TW if explosive gas or vapors are present.
Only the external devices which meet the requirements for SELV equipment according to EN 60950 or IEC
60950 should be connected to the RMO-TW through the serial interface.
When setting up the RMO-TW, make sure that the air slots of the test set remain unobstructed
Removing the RMO-TW protective casing by unauthorized persons will void the warranty. Any work inside
the instrument without prior authorization by DV Power will also void the warranty.
If the RMO-TW seems to be malfunctioning, please contact the DV Power Support Team (refer to the
"Manufacturer Contact Information” section) after previously checking the “Error Messages” section.
Prior to connecting the RMO-TW, ensure that the transformer (object) to be tested is completely deenergized and isolated from both the line and the load. Every terminal should be checked and verified
before connecting the RMO-TW. Ground connections may be left in place.
Do not use the RMO-TW without the extra protective ground cables supplied with the RMO-TW. It must
never be operated in a non-grounded configuration as this may result in an electric shock to the user or
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RMO-TW
Introduction
damage to the RMO-TW. Always establish this connection as the first step before establishing any other
connections, and remove this connection last.
Wherever possible, the outer casing of the transformer under test should also be connected to a safety
earth to prevent the risk of shock. Where this cannot be achieved, adequate precautions should be taken
to prevent access to the transformer (e.g. barriers).
•
Never open the measuring circuit while the test is in progress as dangerous high voltage may
occur.
Never change the De-Energized Tap Changer (DETC) position while the test is in progress.
This can cause excessive voltage arcs within the transformer and on external terminals.
1.2
•
Power Supply
Supply the RMO-TW only from a power outlet which is equipped with protective ground.
•

Besides supplying the RMO-TW from phase-neutral (L1-N, A-N), it may also be supplied from phase to
phase (e.g., L1-L2; A-B). However, the voltage must not exceed 264 V AC. Please refer to the “Technical
Data” section.
The RMO-TW should be positioned in such a way that it is possible to safely disconnect it from the power
supply at any moment.
WARNING / AVERTISSEMENT
This is a class A product. In a domestic environment this product may cause radio interference in which
case the user may be required to take adequate measures.
Il s'agit d'un produit de classe A. Dans un environnement domestique, ce produit peut provoquer des
interferences radio, auquel cas l'utilisateur peut être amené à prendre des measures adéquates.
1.3
Measurement Category
The RMO-TW is intended to be used for measurements in Measurement Category I (CAT I) for voltages up to
300V. The device is also designed to withstand occasional transient overvoltage of up to 1000Vpk.
WARNING / AVERTISSEMENT
This equipment is classified as measurement category I and must not be used within measurement
category II, III and IV.
Cet équipement est classé dans la I catégorie de mesure, et ne doit pas être utilisé pendant les
catégories de mesure II, III et IV.
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1.4
Introduction
Intended Use
The Winding Ohmmeter RMO-TW is a stand-alone or PC-controlled digital instrument designed for detailed
analysis of on-load tap changers and for measuring resistances of inductive test objects used in the electric
power industry or similar industries. It is employed for resistance measurement during the manufacturing,
commissioning and testing of:






transformers,
on-load tap changers,
de-energized tap changers,
generators and electrical motors,
high current busbar joints,
cable splices.
The RMO-TW is also used to create the automatic resistance/temperature measurement for the Heat Run test
together with the DV-Win software.
Any uses of the RMO-TW other than the ones mentioned above are considered improper and will invalidate
warranty claims.
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Description
2 Description
2.1
Front and Rear Panel Components
Figure 2-1:
Front panel of the
instrument
1. Operator Control
Display
Displays the settings during the device test mode selection as well as the measured values during and
after a test operation.
Keyboard
Used to control the device.
• UP/DOWN buttons are used to navigate and set the test parameters.
• ENTER confirms the defined test parameters, language, time and date, and also navigates through
menus. During the test it is used to switch to the measurement of the next phase.
• STOP stops the test, interrupts the alarm buzzer and to return to the previous menu.
• Ω records the resistance value currently displayed on the screen in the RMO-TW instrument internal
memory
• START starts the test.
• SET scrolls between the Current, TapC and Memory menus.
Green LED
• Lights continuously when the RMO-TW is turned on.
• Flashes when the test can be started.
• Flashes alternately with the red LED during the Current and TapC test.
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Description
Red LED
•
•
•
•
Lights continuously in case of operational error.
Lights continuously during a discharging process.
Flashes alternately with the green LED during the Current and TapC test.
Flashes shortly during a resistance measurement in the TapC test.
2. USB PC Interface
The USB PC interface enables controlling the instrument from a PC and downloading previously recorded
results from the instrument’s internal memory. A USB cable is provided as an accessory.
3. Discharge LED
The red LED remains lit until the accumulated energy of the measured object is reduced to a harmless
level.
CAUTION
While the discharge LED is lit, the measurement cables must not be disconnected.
CAUTION
While disconnecting cables, do not bridge the circuit with your body parts!
In case of shorting a winding for the DRM test, it should be noted that a very small current may remain
flowing through the shorted winding even when the discharging process has finished. For that reason
a person should use only a single hand when disconnecting the shorting cable, to avoid the other hand
creating a return path if touching a transformer. For maximum safety insulating gloves should also be
used.
4. Voltage sense cables terminals
Terminals for connecting up to two pairs of voltage sense cables.
5. Current cables terminals
Terminals for connecting “+ / red” and “- / black” test current cables.
Figure 2-2:
Rear panel of the
instrument
6. Mains Power Connector
Connects the RMO-TW to the mains power supply with a power cord.
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RMO-TW
Description
7. Power Switch
Power switch – Double pole switch

I - In this position, the RMO-TW is connected to the mains power supply.

0 - In this position, the RMO-TW is separated from the mains power supply.
8. Protective Earth Connector
For protection against parasitic currents or voltages, the RMO-TW earth/ground connector should always
be connected to protective ground (PE). Only the originally provided cable should be used for this purpose.
For safety reasons, this connection should be established as the first one before any other
connections and removed last.
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Testing
3 Testing
3.1
Connecting the RMO-TW to a Test Object
Before the RMO-TW has been connected to a test object (e.g. a power transformer), the following steps have
to be taken:
• The test object needs to be disconnected from its circuit in accordance to the national safety regulations
and properly grounded to protective earth.
• The transformer needs to be completely de-energized.
• The RMO-TW itself needs to be properly grounded. To do so, the grounding screw should be connected
to protective earth using the original grounding cable.
• One end of the measured windings needs to be properly grounded. The only exception is in the case of
the YN connection being tested and neutral and earth bonds are mutually connected. In this case, one
side of the measurement circuit should not be earthed because it is not necessary and because it will
incorrectly affect the RMO-TW reading.
Note:
Always connect measuring cables to the RMO-TW instrument first and then to the test
object. When disconnecting, always disconnect the cables from the test object first and then
from the RMO-TW.
The grounding wire PE should be disconnected last.
Not following these instructions may cause life-threatening situations.
Figure 3-1: Connecting a test object to the RMO-TW
With the RMO-TW turned off, the RMO-TW needs to be connected to the test object in such a way that the
measuring cables from the "Voltage Sense" sockets are attached as close as possible to the winding and in
between the current feeding cables. That way, the resistance of cables and clamps is almost completely
excluded from the resistance measurement. When connecting the measuring cables, attention should be
paid to polarity.
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Testing
To maximize the accuracy and measurement repeatability, all clamps need to have a good connection to the
test object.
CAUTION
 For safety reasons, a connection of the device should be always established with the test object in
the way described in this Manual.
 The measuring cables should not be connected after the start of the test.
 The leads should not be disconnected before the discharge LED and the alarm buzzer are off.
The RMO-TW instrument can perform the following tests:
- Current test
- Tap Changer test.
3.2
The Current Test
3.2.1 Setting the Measurement Parameters
After the initial display, the RMO-TW automatically changes to the Current menu and the green LED lights
up.
Test current
Figure 3-2:
The Current
menu
Menu name
Test duration time
Memory
Time and Date
3.2.2 The Measurement Process
To start the measuring sequence, the following values need to be selected:

Test current. The following values can be chosen: 5 mA, 10 mA, 50 mA, 100 mA, 500 mA, 1 A, 2 A, 5
A, 10 A, 15 A(*), 20 A(*), 25 A(**), 30 A(**), 40 A(***) and 50 A(***).
* available with the RMO20TW, RMO30TW and RMO50TW models
** available with the RMO30TW and RMO50TW models
*** available with the RMO50TW model

Memory position. This parameter sets the memory position in which the first measurement results will
be saved. Once the test is completed (either due to time expiration or when pressing STOP), the last
measured result will remain registered in the RMO-TW and the memory position is automatically
switched over to the next memory position. The result can be recalled later by selecting that position
number. Positions 000 - 499 can be selected.
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
Testing
Test duration time. The following values can be selected: 30 s, 60 s, 90 s, 2 min, 3 min, 4 min, 5 min,
6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 30 min, 60 min, 90 min,
unlimited.
The available values are selected by pressing UP/DOWN. The next parameter is selected by pressing RIGHT.
Once the information has been confirmed by pressing ENTER, the Ready screen will be displayed.
The Ready state displays the selected test current and its defined duration. If one of these values needs to be
changed, press STOP to return to the Current menu.
Figure 3-3:
The Ready
screen
The flashing green LED indicates that the RMO-TW is now ready to start the test. Pressing START will
run the test. At the start of the test, a cable connection check is done. If an open circuit is detected, the
alarm will be activated and the appropriate error message will be shown on the display.
During the test, both the green and the red LEDs flash alternately. When the current is stabilized, the
RMO-TW starts the measurement of the test object resistance.
Figure 3-4:
The Charging
screen
The following values are displayed during the test: test current, currently measured resistance values, time
remaining until the end of the test procedure and the active memory position. Two resistance values can be
measured simultaneously.
During the test, it is necessary to wait for the test current stabilization in order to obtain reliable results. The
current stabilization can be tracked by observing the Delta R value on the right side of the screen, or by
observing the resistance values themselves. The Delta R information provided is the deviation of the resistance
Δ which can be used to track the current stabilization process. The closer the Δ is to 0%, the results are more
stable. These values are automatically refreshed every second.
Note: The Current menu is not intended for on-load tap changer testing and the tap changer should not be
operated while testing in this mode. The TapC menu should always be used for tap changer analysis instead.
Figure 3-5:
The Current
menu during
the test
Pressing Ω will save the measured resistance results in the internal memory of the RMO-TW, and the memory
position is automatically switched over to the next memory position. These results can be recalled later by
selecting that position number.
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Testing
The test can be completed in two ways:
-
By pressing STOP,
-
Automatically, after the selected time has expired.
When the test is finished either because the selected time has expired or the STOP button has been
pressed, the RMO-TW switches to the Results menu and starts the discharging process. During the
discharging, the discharge LED lights and the alarm beeps.
Discharge is completed when the discharge LED and the buzzer are OFF. Also, during that period the
“Discharging” message is shown on the display. During the discharging process it is not possible to start
another measurement.
When the test is stopped, the RMO-TW immediately stops producing output voltage. However, because of the
test object inductivity, the current still flows. Because of the enormous amount of energy that can be stored in a
magnetic field, precautions should be taken before disconnecting the test leads from the tested transformer.
Never remove the leads during the testing process and always allow enough time for the tested transformer to
completely discharge. Large transformers can require several minutes to discharge.
CAUTION
DO NOT DISCONNECT LEADS BEFORE THE “DISCHARGING” MESSAGE DISAPPEARS FROM THE
DISPLAY AND THE DISCHARGE LED IS OFF.
ATTENTION
NE PAS DÉBRANCHER LES CONDUCTEURS AVANT QUE LE MESSAGE
''DÉCHARGER/DISCHARGING'' EST DISPARU DE L'ÉCRAN ET QUE LA DIODE DE DÉCHARGE EST
ÉTEINTE.
3.2.3 Viewing the Test Results
Once the test is finished, the RMO-TW automatically changes to the Results menu to display the test results.
Figure 3-6:
The Results menu
showing the test results
3.3
The Tap Changer Test
The winding resistance of individual taps of a power transformer’s tap changer can be measured by using the
Tap Changer (TapC) mode of the RMO-TW. There is no need to charge and discharge the transformer
between tap position changes. The inputs of the instrument are protected during the switching process in order
to avoid damage to the instrument in case of a faulty tap changer.
The RMO-TW injects a constant current into the power transformer. The winding resistance is calculated from
this current value and the measured voltage value. An interruption caused by a defective tap changer results in
comparatively high measured values of the current ripple.
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Testing
Figure 3-7:
Connecting a test
object to the
RMO-TW
3.3.1 Setting the Measurement Parameters
Turn on the RMO-TW with the power switch on the back of the test set. The display shows the
Current menu and the green LED lights up. Press SET to go to the TapC menu.
Test current
Figure 3-8:
The TapC
menu
Menu name
Memory position
Active channel
Time and Date
In the TapC menu, the following values need to be defined:
•
Test current. The following values can be selected: 1 A, 2 A, 5 A, 10 A, 15 A(*), 20 A(*).
* available with the RMO20TW, RMO30TW and RMO50TW models
•
Memory position. This parameter sets the memory position in which the first measurement results will
be saved. Once the test is completed, the last measured result will remain saved in the RMO-TW, and
the memory position is automatically switched over to the next memory position. The result can be
recalled later by selecting that position number. Positions 000 - 499 can be selected.
The available values are selected by pressing UP/DOWN. The next parameter is selected by pressing RIGHT.
Once the information has been confirmed by pressing ENTER, the Ready screen will be displayed.
Figure 3-9:
The Ready screen
The Ready state displays the selected test current and memory location. If one of these values has to be
changed, press STOP to return to the TapC menu.
Note: Only CH1 (the upper channel) is active during the TapC measurement.
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Testing
3.3.2 Tap Changer Test with the RMO-TW
The flashing green LED indicates that the RMO-TW is now ready to start the test. Press START to run a
test. At the start of the test, a cable connection check is done. If an open circuit is detected, the alarm is
activated and the error message is shown on the display
During the period of current stabilization, both the green and the red LEDs flash alternately and the
message “PLEASE WAIT CHARGING” is shown on the display.
The following values are displayed during this part of the test: the test current, the effective value of the
measured resistance, and the active memory position. The current stabilization can be tracked by observing
the Delta R value on the right side of the screen, or by observing the resistance values themselves. These
values are automatically refreshed every second.
Figure 3-10:
The TapC
menu when the test
current is stabilized
At the moment the resistance result is stable, the resistance value of the on-load tap changer starting position
can be saved by pressing Ω. The memory position is automatically switched over to the next one and the
device is ready to record the current ripple.
While the resistance value is being saved, the red LED flashes shortly and the beeper sounds in higher
speed intervals.
Figure 3-11:
The TapC menu,
“Change tap position”
message
The RMO-TW detects the change of the test current during the tap position change and measures the
difference between the starting current and the lowest value it reaches during the transition. This value is called
the transition ripple, and it is indicated as a percentage of the starting current value.
Figure 3-12:
The TapC menu,
memory location is
increased by one
The display shows the test current value in the new tap position (here 9.82 A), and the value of the current
ripple which occurred during the change from the previous position to the new one (here 4.7 %). The current
stabilization can be followed on the display. After it has been stabilized, the RMO-TW shows the resistance
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Testing
value in the new tap position (here 576.4 mΩ). Pressing Ω will save the resistance and the ripple in the new tap
changer position.
This procedure is repeated until the ripples and resistance values are obtained for all the tap changer positions.
The tap changer test is completed by pressing STOP. The transformer is then automatically discharged.
During the current discharging process, the discharge LED lights and the alarms beep. Discharge is
completed when the discharge LED and the buzzer are OFF. It is not possible to start another
measurement during this process.
CAUTION

DO NOT DISCONNECT LEADS BEFORE THE “DISCHARGING” MESSAGE DISAPPEARS FROM
THE DISPLAY AND THE DISCHARGE LED AND BUZZER ARE OFF.
Figure 3-13:
The TapC menu during
discharging
A properly working tap changer differs from a malfunctioning one by the magnitude of the current ripple value.
An open circuit during the transition will result in a much higher current ripple value (99 % or 100 %) than a
properly functioning tap changer.
Note:
The current ripple value depends on the construction of the tap changer. It is recommended to compare
current ripple values to the values of other tap transitions in the same measurement. It is also recommended to
compare the current ripple results with the reference results from a previous tap changer test on the same
transformer.
The figure below shows an indication of possible tap changer discontinuity during the tap position change from
one tap position to the next one.
Figure 3-14:
The TapC menu
showing a much higher
current ripple value
If the current circuit is interrupted during the tap position change, the „Discontinuity“ message will be shown on
the display, the red LED will light and the buzzer will beep continuously. The discharging process will be
initiated.
Figure 3-15:
The "Discontinuity"
message
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3.4
Testing
Measurement Parameters
The highest resolution of the reading is always displayed. The resistance range selection is performed
automatically and therefore manual setting by the operator is not necessary.
Table 3.1: Maximum resistances for each test current
Test
Current
Max Test
Voltage
RMO10TW
Max Test
Voltage
RMO20TW
Max Test
Voltage
RMO30TW
Max Test
Voltage
RMO50TW
Max
Resistance
RMO10TW
Max
Resistance
RMO20TW
Max
Resistance
RMO30TW
Max
Resistance
RMO50TW
5 mA
10 mA
50 mA
100 mA
500 mA
1A
2A
5A
10 A
15 A
20 A
25 A
30 A
40 A
50 A
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
-
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
37,5 V
-
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
42.5 V
34 V
28.33 V
-
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
50 V
40 V
33.3 V
25 V
20 V
10 kΩ
5 kΩ
1 kΩ
500 Ω
100 Ω
50 Ω
25 Ω
10 Ω
5Ω
-
10 kΩ
5 kΩ
1 kΩ
500 Ω
100 Ω
50 Ω
25 Ω
10 Ω
5Ω
3.33 Ω
1.87 Ω
-
10 kΩ
5 kΩ
1 kΩ
500 Ω
100 Ω
50 Ω
25 Ω
10 Ω
5Ω
3.33 Ω
2.125 Ω
1.36 Ω
944 mΩ
-
10 kΩ
5 kΩ
1 kΩ
500 Ω
100 Ω
50 Ω
25 Ω
10 Ω
5Ω
3.33 Ω
2.5 Ω
1.6 Ω
1.11 Ω
625 mΩ
400 mΩ
Table 3.2: Resolution and full scale for each measuring range
Full scale
Resolution
0.1 μΩ – 999.9 μΩ
0.1 μΩ
1.000 mΩ – 9.999 mΩ
1 μΩ
10.00 mΩ – 99.99 mΩ
10 μΩ
100.0 mΩ – 999.9 mΩ
0.1 mΩ
1.000 Ω – 9.999 Ω
1 mΩ
10,00 Ω – 99.99 Ω
10 mΩ
100.0 Ω – 999.9 Ω
0.1 Ω
1.000 kΩ – 9.999 kΩ
1Ω
Typical accuracy of the RMO-TW instruments is ±(0.1% rdg + 0.1% F.S) for 0.1 μΩ – 1.999 kΩ range, and
±(0.2% rdg + 0.1% F.S) for 2.000 kΩ – 9.999 kΩ range. These accuracies are valid if the maximum possible
current is used. As high current as possible should always be selected, but to avoid the risk of heating the
winding, it is recommended not to exceed from 10 % to 15 % of the transformer nominal current. It is important
to make a good connection between the clamps and the connecting points on the test object to achieve stable
and accurate test results.
The guaranteed accuracy of the RMO-TW instruments is ± (0.2 % rdg + 0.2 % F.S).
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Error Messages
4 Error Messages
Any operational error is indicated by a red LED and accompanied by an alarm. Furthermore, the display
indicates an error status message. To stop the alarm buzzer and return to the test menu, the status message
should be removed from the display by pressing STOP.
4.1
Error Message "Open Connection"
The Error message "Open Connection" is displayed if the current path is interrupted.
Figure 4-1: An example of interruption of the current path – a current cable disconnection
Figure 4-2:
Error message
"Open Connection"
4.2
Error Messages "Connection CH1-2-3" and "Connection CH1"
The Error message "Connection CH1-2-3" is displayed if channel 1and channel 2 are all disconnected. This
message is displayed if either + or – voltage sense cable or both are disconnected either on the device side or
on the side of the test object.
Figure 4-3:
Error
message
"Connection"
The Error message "Connection CH1" is displayed only if CH1 is not connected during the tap changer testing.
This message is displayed if either + or – voltage sense cable or both are disconnected either on the device
side or the side of the test object.
These messages can be displayed only at the beginning of the test.
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4.3
Error Messages
Error Message "Polarity"
The Error message "Polarity" is displayed if the voltage sense cables are connected with opposite polarity
either on the side of a device or the side of a test object, and the measured voltage signal is higher than 60
mV. Unlike other error messages, the test will not be interrupted. A “Polarity” warning will be displayed as
shown on the figure below.
Figure 4-4:
Error message
"Polarity"
Note: Since 60 mV is the signal threshold, the display will show the result with lower accuracy for lower voltage
signal values. If some of the cables are disconnected after starting the test, the error message will not show up
and the received results will be erroneous.
4.4
Error Messages "Change Current" and “Overcurrent”
This message is displayed if the voltage at the test object is too high during the test. In this case the test
current should be reduced and the test repeated.
Figure 4-5:
Error message
"Change Current"
The error message “Overcurrent” is displayed if the test voltage is lower than 10 V per channel but the test
current is still too high for that resistance. An user should re-start the test with lower test current selected.
Figure 4-6:
Error message
"Overcurrent"
4.5
Error Message "Overheat"
This message is displayed when the operating temperature of the RMO-TW rises too high. In this case, it is
necessary to wait for the test set to cool down and repeat the test.
Figure 4-7:
Error message
"Overheat"
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4.6
Error Messages
Error Message "Mains Voltage < 90V"
This message is displayed when the RMO-TW mains voltage is below 90 V.
Figure 4-8:
Error message
"Mains Voltage < 90V"
The RMO-TW should be restarted to reset the status message.
4.7
Error Messages "Error Printer" and "Check Paper"
The message "Error printer" is displayed if a hardware error of the printer is detected. The position of the black
shaft should be checked. If it is in proper position and the error keeps occurring repeatedly, please contact DV
Power Support Team (please refer to the ”Manufacturer Contact Information” section of this Manual).
Figure 4-9:
Error messages
"Error printer" and
"Check paper"
The message "Check paper" is displayed if the printer is out of paper.
The paper roll should be aligned with the paper intake so that there is no horizontal offset, and the central axis
of the paper roll must be parallel to the printer as shown in the Figure 4-10. Also, attention should be paid when
inserting the paper into the printer. It should enter the paper intake from the lower side of a paper roll.
If the paper is not properly aligned, the black shaft should be pulled up to loosen the paper (see the Figure 410). After that, the paper should be aligned and the black shaft pushed down into a proper position.
Figure 4-10:
Paper loading
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Troubleshooting
5 Troubleshooting
If suspected the device is presenting inaccurate results, the following tests should be performed:
5.1
Accuracy Check
1. Connect the test shunt R1 (1 Ω) and the Voltage Sense cables (VS1 input) as shown in the Figure 5-1.
2. Set the first test current from the Table 5.1 and start the test. Read the resistance value measured with the
Winding Ohmmeter and compare it to the expected value written in the Table 5.1. Repeat this step for all
test currents from the Table 5.1.
3. Connect the test shunt R2 (1 mΩ) and Voltage Sense cables (VS1 input) as shown in the Figure 5-2.
4. Set the first test current listed in Table 5.2 and start the test. Read the resistance value measured with the
Winding Ohmmeter and compare it with the expected value written in the Table 5.1. Repeat this step for all
test currents from the Table 5.2.
5. Connect the Voltage Sense cables to the VS2 input and repeat steps 1-4.
6. If measured results differ from expected values, please proceed to the next step – determining the root
cause of the inaccurate measurements.
Figure 5-1 – Connection diagram
I [mA]
10
100
1000
Figure 5-2 – Connection diagram
R1 [Ω]
0.989 – 1.011
0.989 – 1.011
0.989 – 1.011
I [A]
2
5
10
Table 5.1 – Expected results
5.2
R2 [mΩ]
0.989 – 1.011
0.989 – 1.011
0.989 – 1.011
Table 5.2 – Expected results
Open Circuit Voltage Check
1. Short circuit the Voltage Sense input (VS1) and connect a DC voltmeter directly between current terminals
of the Winding Ohmmeter, as shown in the Figure 5.3.
2. Set the test current of 10 A and start the test. Check if the voltage measured with the voltmeter is in range
55 – 65 VDC.
3. Check if any resistance measurement value is shown on the device display and if the discharge LED is ON.
4. After 120 seconds the device should display the Open connection error.
5. If the measured voltage is not in the range 55 – 65 VDC, please contact the DV Power Support Team.
Otherwise, please proceed to the next step.
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Troubleshooting
Note: Discharge LED should not light during this
test.
Expected voltage: 55 VDC – 65 VDC
Figure 5.3 – Open circuit voltage check
5.3
Test Currents Check
1. Short circuit Voltage Sense input (VS1) of the device and connect a digital voltmeter in parallel to the R1 (1
Ω) test shunt as shown in the Figure 5.4.
2. Set the first test current listed in the Table 5.3 and start the test. Note the voltage V1 obtained with the
voltmeter and compare it with expected one: 𝑉1 = 𝐼 ∙ 𝑅1 . Repeat this step for all test current listed in the
Table 5.3.
3. Short circuit Voltage Sense input (VS1) of the device and connect a digital voltmeter parallel to the R2 (1
mΩ) test shunt as shown in the Figure 5.5.
4. Set the first test current listed in the table 5.4 and start the test. Note the voltage V2 obtained with the
voltmeter and compare it to the expected one: 𝑉2 = 𝐼 ∙ 𝑅2 . Repeat this step for all test current listed in Table
5.4.
5. If the measured voltages do not differ significantly from the expected ones, the device is generating the
current correctly. Please proceed to the next step.
Figure 5.4 – Connection diagram
I [mA]
10
100
1000
Figure 5.5 – Connection diagram
V1[mV]
9.89 – 10.11
98.9 – 101.1
989 – 1011
I [A]
2
5
10
Table 5.3 – Expected results
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R2[mV]
1.978 – 2.022
4.945 – 5.055
9.89 – 10.01
Table 5.4 – Expected results
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5.4
Troubleshooting
Voltage Measurement Check
1. Connect the test shunt R1 (1 Ω), Voltage Sense cables (VS1 input) and voltmeter as shown in the Figure
5.6.
2. Set the first test current listed in Table 5.5 and start the test. Note the resistance measured with the device
(R1meas), the voltage V1 measured with the voltmeter, and calculate the resistance: 𝑅1𝑐𝑎𝑙 =
𝑉1
.
𝐼
Repeat this
step for all test currents listed in Table 4.1.
3. Connect the test shunt R2 (1 mΩ), Voltage Sense cables (VS1 input) and voltmeter as shown in the Figure
5.7.
4. Set the first test current listed in Table 5.6 and start the test. Note the resistance measured with the device
(R2meas), the voltage V2 measured with the voltmeter, and calculate the resistance: 𝑅2𝑐𝑎𝑙 =
𝑉2
.
𝐼
Repeat this
step for all test currents listed in Table 5.6.
5. Connect the Voltage Sense cables to the VS2 input and repeat steps 1-4.
6. If calculated resistances do not differ significantly from the resistances measured with the RMO-TW device,
the device is measuring correctly.
Figure 5.6 – Connection diagram
I [mA]
10
100
1000
R1meas[Ω]
0.989 – 1.011
0.989 – 1.011
0.989 – 1.011
Figure 5.7 – Connection diagram
V1[mV]
9.89 – 10.11
98.9 – 101.1
989 – 1011
I [A]
2
5
10
Table 5.5 – Expected results
5.5
R2meas[mΩ]
0.989 – 1.011
0.989 – 1.011
0.989 – 1.011
V2[mV]
1.978 – 2.022
4.945 – 5.055
9.89 – 10.01
Table 5.6 – Expected results
TestCom Diagnostic Software
In case the TestCom diagnostic software is not provided, please contact the DV Power Support Team to
request the latest version.
1. Connect the device to the computer and turn it ON.
2. Run the TestCom.exe file.
3. Click Connect to establish communication between the device and the computer.
4. Click Start and a log file will be generated in the same folder where TestCom.exe is located.
5. Send the log file to DV Power Support Team for analysis.
NOTE: If experiencing problems with running TestCom.exe, please install the Patch.exe, which is
included in the TestCom archive. After the installation, it should be possible to run TestCom.exe.
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Customer Service, Packing the Instrument for Shipment
6 Customer Service
Before calling or sending an e-mail to Customer Service for assistance, please perform the following steps:
1. Check all cable connections.
2. Try the test on another instrument, if available.
3. Perform the troubleshoot procedure
4. Have the following information available:
•
Instrument serial numbers, hardware configuration, and software revision
•
Exact description of the problem, including the test object information, error messages and the
sequence of events before it appeared
•
List of solutions that have been tried
The Customer Support Department can be reached at:
Local support (Sweden): +46 8 731 78 24
International support: +46 70 0925 000
E-mail: support@dv-power.com
Note: Email communication is preferred for support issues, since the case is then documented and traceable.
Also, the time zone problems and issues with occupied telephones do not occur.
7. Packing the Instrument for Shipment
If you need to send the instrument to DV Power for servicing, please contact the DV Power Customer Service
for return instructions at:
Local support (Sweden): +46 8 731 78 24
International support: +46 70 0925 000
E-mail: support@dv-power.com
Note: DV Power is not responsible for shipping damage. Please protect each instrument from shipping and
handling hazards carefully. Please ensure protective covers are securely in place. Instruments should be sent
to DV Power freight pre-paid, unless other arrangements have been authorized in advance by DV Power
Customer Service.
To prepare an instrument for shipment, please follow these instructions:
1. Disconnect and remove all external cables. Do not include manuals and cables unless recommended by DV
Power Customer Service.
2. Reuse the original packing material if it is available. If it is not, pack the instrument for shipment according to
the instructions for fragile electronic equipment. It is recommended use two-wall minimum corrugated
cardboard box with a minimum 5 cm (2 inch) thick poly foam padding, or a wooden crate with minimum of 5 cm
(2 inch) thick poly foam padding all around.
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Technical Data, Instrument & Accessories, Manufacturer Contact Information
8 Technical Data
8.1
Mains Power Supply
- Connection:
- Voltage:
- Input power
according to EN60320-1/C320
90 V – 264 V AC, 50/60 Hz, Single phase
750 VA (RMO10TW model), 1500 VA (RMO20TW model), 2250
VA (RMO30TW and RMO50TW models)
15 A / 250 V, type F, but not user replaceable
- Fuse
8.2
Output Data
- Test current
RMO10TW
RMO20TW
RMO30TW
RMO50TW
5 mA – 10 A DC
5 mA – 20 A DC
5 mA – 30 A DC
5 mA – 50 A DC
- Output power
8.3
Instrument
RMO10TW
RMO20TW
RMO30TW
RMO50TW
Output power
600 W
750 W
850 W
1 000 W
Measurement
- Measuring range / Resolution
0.1 µΩ - 999.9 µΩ
1.000 mΩ - 9.999 mΩ
10.00 mΩ - 99.99 mΩ
100.0 mΩ - 999.9 mΩ
1.000 Ω - 9.999 Ω
10,00 Ω - 99.99 Ω
100.0 Ω - 999.9 Ω
1.000 kΩ - 9.999 kΩ
0.1 µΩ
1 µΩ
10 µΩ
0.1 mΩ
1 mΩ
10 mΩ
0.1 Ω
1Ω
- Typical Accuracy:
± (0.1 % rdg + 0.1 % FS) for 0,1 μΩ – 1,999 kΩ range
± (0.1 % rdg + 0.2 % FS) for 2.000 kΩ – 9,999 kΩ range
- Guaranteed Accuracy
± (0.2 % rdg + 0.2 % FS)
8.4
Environmental Conditions
o
o
o
o
- Operating temperature
-10 C - +55 C / 14 F - +131 F
- Storage temperature
- Humidity range
-25 C - +70 C / -13 F - +158 F
5 - 95%, non-condensing
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8.5
Dimensions and Weight
Dimensions without
handle (cm)
Dimensions without
handle (in)
Weight (kg)
Weight (lbs)
8.6
Technical Data, Instrument & Accessories, Manufacturer Contact Information
RMO10TW
RMO20TW
RMO30TW
RMO50TW
19.8 x 25.5 x 38
19.8 x 25.5 x 38
19.8 x 25.5 x 38
19.8 x 25.5 x 38
7.8 x 10 x 15
7.8 x 10 x 15
7.8 x 10 x 15
7.8 x 10 x 15
7.5
16.5
7.5
16.5
8.5
18.7
8.5
18.7
Applicable Standards
- Installation/overvoltage
- Pollution
- Safety
category II
degree 2
UL 61010-1
CAN/CSA-C22.2 No. 61010-1, 2nd edition, including
Amendment 1
Directive 2004/108/EC (CE Conform)
Standard EN 61326-1
- EMC
All specifications herein are valid at the ambient temperature of + 23 °C ± 5°C and by using the recommended accessories.
Specifications are subject to change without notice.
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Technical Data, Instrument & Accessories, Manufacturer Contact Information
9 Instrument & Accessories
Instrument with included accessories
Article No
Winding Ohmmeters RMO-TW
RMOXX0TW-N00
- DV-Win PC software including USB cable
- Mains power cable
- Ground (PE) cable
Recommended accessories
Article No
2
Current cables 2 x 10 m 10 mm and Sense cables 2 x 10 m with TTA clamps *
2
Current cables 2 x 10 m 2.5 mm and Sense cables 2 x 10 m with TTA clamps **
Sense cables 2 x 10 m with TTA clamps
2
Current connection cable 5 m 6 mm with TTA clamps *
2
Current connection cable 5 m 10 mm with TTA clamps **
Device bag
Cable bag
CS-10-10LMWC
CS-10-02BPWC
S2-10-02BPWC
CX-05-062XWC
CX-05-102XWC
DEVIC-BAG-00
CABLE-BAG-00
* recommended for the RMO10TW and RMO20TW models
** recommended for the RMO30TW and RMO50TW models
Optional accessories
Article No
Test shunt 1 mΩ (150 A / 150 mV)
2
Current cables 2 x 15 m 10 mm and Sense cables 2 x 10 m with TTA clamps
2
Current cables 2 x 20 m 16 mm and Sense cables 2 x 10 m with TTA clamps
2
Current cables 2 x 10 m 10 mm with TTA clamps
2
Current cables 2 x 15 m 10 mm with TTA clamps
2
Current cables 2 x 20 m 16 mm with TTA clamps
Sense cables 2 x 15 m with TTA clamps
Sense cables 2 x 20 m with TTA clamps
2
Current connection cable 12 m 16 mm
Thermal printer 80 mm (built-in)
Cable plastic case
Cable plastic case with wheels
Transport case
Bluetooth communication module
SHUNT-150-MK
CS-15-16LMWC
CS-20-16LMWC
C2-10-16LMWC
C2-15-16LMWC
C2-20-16LMWC
S2-15-02BPWC
S2-20-02BPWC
CX-12-162XWC
PRINT-080-00
CABLE-CAS-01
CABLE-CAS-W1
HARD-CASE-RT
BLUETOOTH-00
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Technical Data, Instrument & Accessories, Manufacturer Contact Information
IBEKO Power AB 2014
This Manual is a publication of IBEKO Power AB, 181 50 Lidingö, Sweden. These documents are protected by Swedish
Copyright law and international contracts as intellectual property of the IBEKO Power AB. The documents contain
confidential information of IBEKO Power AB which is protected by patent, copyright, trademarks or otherwise as
inventions, trademarks or creations of IBEKO Power AB. The reproduction, duplication, transmission or use of these
documents or its contents is not permitted without express prior written consent of the IBEKO Power AB.
IBEKO Power AB shall not be liable for any incidental or consequential damages resulting from the performance or use of
this document or its product. This document has undergone extensive technical approval before being released. IBEKO
Power AB reviews this document at regular intervals, and includes appropriate amendments in subsequent issues. While
every effort has been made to keep the information herein as accurate and up to date as possible, IBEKO Power AB
assumes no responsibility for errors or omissions or for damages resulting from the use of the information contained
herein. IBEKO Power AB cannot take over liability resulting in any way from the use of this document or parts thereof. The
product information, pictures, drawings and all technical data contained within this manual are not contractually binding
and IBEKO Power AB reserves the right to make modifications at any time to the technology and/or configuration without
prior notice.
Insofar as any information, software or documentation is made available, any liability for defects as to quality or title of the
information, software and documentation especially in relation to the correctness or absence of defects or the absence of
claims or third party rights or in relation to completeness and/or fitness for purpose are excluded except for cases involving
willful misconduct or fraud.
In case of a disagreement between the translation and the original English version of this Manual, the original English
version will prevail.
Manufacturer Contact Information
IBEKO Power AB
Box 1346, 181 25 Lidingö, Sweden
Fax:
+ 46 8 731 77 99
E-Mail: support@dv-power.com
Website: http://www.dv-power.com
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