IBEKO POWER DV Power RMO25T User manual
RMO25T
W I N D I N G O H M M E T E R
&
T A P C H A N G E R T E S T S E T
Manual
IBEKO POWER AB
2
RMO25T Contents
Contents
1Introduction..........................................................................................................................................3
2Safety Instructions..............................................................................................................................3
3Designated Use...................................................................................................................................4
4Functionality.........................................................................................................................................4
5Description...........................................................................................................................................7
6Getting Started..................................................................................................................................10
7DV-Win Software ..............................................................................................................................21
8Error Messages.................................................................................................................................36
9Technical Data ..................................................................................................................................39
10 Accessories........................................................................................................................................40
Manufacturer Contact Information..........................................................................................................40
Manual Version: RMO25T. MV.RT2P-6.12
This Manual refers to the firmware version RT2P-6.12
IBEKO POWER AB 2010
This Manual is a publication of IBEKO POWER AB, 181 33 Lidingö, Sweden.
All rights including translation reserved. Reproduction of any kind, e.g., photocopying, microfilming or storage in
electronic data processing systems, requires the explicit consent of IBEKO POWER AB. Reprinting, wholly or in
part, is not permitted.
This Manual represents the technical status at the time of printing. The product information, specifications, and all
technical data contained within this Manual are not contractually binding. IBEKO POWER AB reserves the right to
make changes at any time to the technology and/or configuration without announcement. IBEKO POWER AB is not
to be held liable for statements and declarations given in this Manual. The user is responsible for every application
described in this Manual and its results.
IBEKO POWER AB explicitly exonerates itself from all liability for mistakes in this Manual.
IBEKO POWER AB translates this Manual from its source language English into a number of other languages. Any
translation of this Manual is done for local requirements, and in the event of a dispute between the English and any
non-English versions, the English version of this Manual shall govern.
3
RMO25T Introduction, Safety Instructions
1 Introduction
This Manual contains helpful instructions on how to use RMO25T in a safe, proper and efficient way.
Following these instructions can help you avoid dangerous situations, repair costs and other miss
happenings due to incorrect operation. Furthermore it ensures the reliability and life cycle of your
RMO25T.
RMO25T must be used in observance of all existing safety requirements and regulations from
national/local standards for accident prevention and environmental protection.
Reading the RMO25T Manual alone does not exempt the user from the duty of complying with all
national and international safety regulations relevant for working with RMO25T.
2 Safety Instructions
Before operating RMO25T, please read carefully the following safety instructions.
It is not recommended that the RMO25T is used (or even turned on) without the understanding of this
Manual.
RMO25T should only be operated by trained and authorized personnel.
Rules for Use
RMO25T should only be used when in a technically fit condition. Its use should be in accordance with
the safety regulations for the actual working site and application. Always be aware of the dangers of
high voltages and currents associated with this equipment and its environment. Pay attention to the
information provided in the Manual.
RMO25T is intended exclusively for the application areas specified in
manufacturer and distributors are not liable for damage resulting from wrong usage. The user alone
assumes all responsibility and risk.
The instructions provided in this Manual are considered part of the rules governing proper usage.
Do not open RMO25T. All service and maintenance work must be performed by qualified
personnel.
Orderly Practices and Procedures
The Manual should always be available on the site where the RMO25T is used.
Before using RMO25T, all personnel (even personnel who only occasionally, or less frequently, work
with RMO25T) assigned to RMO25T should read the operations Manual.
Do not undertake any modifications, extensions, or adaptations to the RMO25T.
Use RMO25T in conjunction with original accessories only.
Use both RMO25T and its original accessories for its designated use only.
Cleaning
To clean RMO25T, use a cloth dampened with isopropanol alcohol or water.
Operator Qualifications
Testing with RMO25T should only be carried out by authorized and qualified personnel.
Personnel receiving training, instruction, direction or education on the RMO25T should remain under
the constant supervision of an experienced operator while working with the test set and the test
object.
4
RMO25T Designated Use, Functionality
Safe Operation Procedures
Hazardous voltages of up to 400 V can occur inside RMO25T. Therefore, it is not permitted to open
RMO25T.
Do not insert objects (e.g., screwdrivers, etc.) into the ventilation slots.
Before putting RMO25T into operation, check the test set for any visible damage.
Do not operate RMO25T under wet or moist conditions (condensation).
Do not operate RMO25T when explosive gas or vapors are present.
The serial interface of RMO25T should only have external devices connected that meet the
requirements for SELV equipment according to EN 60950 or IEC 60950.
When setting up RMO25T, make sure that the air slots of the test set remain unobstructed.
If RMO25T is opened by the customer, all guarantees are invalidated.
If RMO25T seems to be functioning improperly, please contact the IBEKO POWER AB (refer to
after first checking the section Error Messages.
Do not use RMO25T without the extra protective ground cables for RMO25T and winding connection.
Always establish this connection as the first one before you do any other connections, and separate
this connection as the very last one.
Never open the measuring circuit while current flows as dangerous high voltage may occur. This
is indicated by the red discharge LED and the beeper.
Power Supply
Supply RMO25T only from a power outlet that is equipped with protective ground.
Instead of supplying RMO25T 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 240 V AC, please refer to the
section Technical Data.
3 Designated Use
The Winding
Ohmmeter RMO25T is designed for measuring resistances of inductive test objects used in
the electric power industry or similar industries. It is employed for resistance measurement during
manufacturing, commissioning and testing of:
transformers,
on-load tap changers,
generators and electrical motors,
high current busbar joints,
cable splices.
Any other use of the RMO25T than the ones mentioned above is to be considered improper and will not
only invalidate all customer warranty claims but also exempt the manufacturer from its liability for repair
or exchange.
4 Functionality
4.1 Current Test
The RMO25T generates a filtered (true) DC current.
RMO25T test set can measure the winding resistance of any transformer; small or very large, single or
three phase, star, delta or zig-zag connected. There are two independent measuring channels which can
be used to simultaneously measure resistance of up to two windings at the same time.
Choose the test current so that the maximum value is obtained for the expected resistance (refer
to section 6.1).
5
RMO25T Designated Use, Functionality
The inductance value of a transformer depends on the current injected in the windings. When the
transformer is saturated the inductance is minimized. A transformer is normally designed to reach
saturation when the current is 1,2 times the peak value of the no-load current. The no-load current is
normally in the range of 0,2 % to 5 % of the nominal winding current.
When measuring the DC resistance, the test current should be at least 1,2 times the no-load current of
the transformer. This is to ensure that the transformer core is saturated. Note also that the test current is
NOT to exceed approximately 10 % to 15 % of the nominal winding current.
Note: The Voltage sense measuring channels are automatically selected connecting measuring cables
to those channels.
At the start of each test a check of cable continuity is done. In case of open circuit, an alarm is activated,
and the error message is shown on the display.
The test is started by pressing the START button. The RMO25T injects current with a voltage as high as
60V. This ensures the test to be as short as possible and that the desired test current is reached faster.
When the current is stabilized, RMO25T measures the resistance of the test object. The test result is
displayed as R=U/I. During the testing period, a new result is shown on the display approximately each
second.
Tests could be finished or interrupted two ways:
- Pushing the STOP button,
- Automatically, after the selected time has expired.
In both cases, upon completion of the test, a measured value of the resistance is recorded to pre-
selected internal memory location.
Each time the Ωbutton is pushed, results of the resistance, the ripple and the test current value are
stored into the internal memory of RMO25T, and memory location changes to the next one.
Minimum measurement time is 30 seconds.
By pushing the STOP button test could be completed at any time. When the STOP button is pushed, the
last measured result will remain saved in the internal memory.
After selected test time has expired, the last result remains saved at selected memory location.
Note: Using DV-Win the results could be stored to a PC, where reading interval of results is adjustable.
Results will be shown in a table in Excel format with an option to perform additional edit and
graphic presentation.
Using DV-Win after the test in order to transfer the results from selected internal memory location to a
PC, will allow transfer of the last test result only.
When the measurement is complete, RMO25T starts discharging the energy from the inductance. During
current discharging, the red discharge LED is lit and the buzzer is ON. Discharge is complete when the
discharge LED and the buzzer are OFF and when discharging message is disappeared from the display.
Both, injection of current and discharging energy from the inductance is fully automatically regulated. An
intrinsically safe discharge circuit, with indicator, dissipates the stored magnetic energy rapidly after the
test. The discharging circuit is independent of power supply.
Cooling of RMO25T is supported by a built-in fan that is automatically activated when the device is
turned on.
6
RMO25T Designated Use, Functionality
4.2 Tap Changer Test
The TapC menu offers a user friendly way of measuring winding resistance in tap changers. The
RMO25T test set measures
changer, and checks whether the On-Load Tap Changer (OLTC) switches without a discontinuity. In the
moment the tap is changed from tap to tap, the device detects the sudden, very short drop of the current
flow. A properly working tap changer differs from a malfunctioning one in a discontinuity during the
change, by the magnitude of the current ripple value.
and comparing with other phases, allows for an efficient analysis. Disposition of all current ripple
changes (or of the current flow on the graph) depends on a particular transformer and OLTC design, so it
is always recommended to compare results obtained on the same unit with previous measurements.
Note: In TapC menu only Ch:1 is the active channel. Maximum test current selected in the TapC mode
is 20 A.
At the start of the test a check of cable continuity is performed. In case of disconnection, an alarm is
activated, and the error message is shown on the display.
Note: Using DV-Win in TapC menu the results could be stored to a PC. By pushing the Ωbutton a
resistance result and current ripple value are stored in internal memory location, and the memory
location is automatically increased to the next one.
7
RMO25T Description
5 Description
5.1 Front Panel Components
STOP button
Press to stop a test or stop the alarm buzzer.
START button
Press to start a test
Test parameters must be selected beforehand
Pressing the START button at the same time with the SET button allows you to go to setting menu for the
language, time and date settings.
Ωbutton
Press to measure the resistance current value.
Press to measure the resistance value in TapC mode
Green LED
RMO25T is turned on.
t.
Red LED
s alternately with the green LED during the TapC test.
Red LED - Discharge
The red LED just above the red output connector remains lit until the accumulated energy of the
measured object is reduced to a harmless level
CAUTION
Within the period when the discharge LED lights it is prohibited to disconnect measuring cables.
The discharge diode could not be switched off by the STOP button.
Display
UP/DOWN buttons
to select a menu
and set test
parameters
RIGHT buttons to navigate
in the active menu
ENTER button to
confirm the defined test
parameters, Language,
Time and Date
STOP button to stop a test, to
acknowledge the alarm buzzer and
return to the Curr menu.
Ωbutton to measure the
resistance current value and the
resistance and the ripple value in
TapC mode.
START button to
start the test
current.
SET button to
scroll between
the Current
menu, the TapC
menu and the
Memory menu
8
RMO25T Description
5.2 Mains power and ground connectors
5.3 Settings
To set RMO25The START button at the same time with the SET button,
to select the Setting menu.
Setting RMO25T’s Language
To set RMO25T language, use the RIGHT button, and then the ENTER buttons to select the Set
Language menu.
Move the cursor to the bottom line using the LEFT/RIGHT buttons, and select the language with the
ENTER button.
Pressing ENTER to confirm, returns you to the Main menu.
Pressing STOP to cancel, returns you to the Main menu.
Setting RMO25T’s Time and Date
To set RMO25Ts internal time and date, use the RIGHT button, and then the ENTER button to select the
Set Time and Date menu.
Connector for mains power supply
Power switch
I In this position, RMO25T is connected to the
mains power supply.
0 In this position, RMO25T is separated from
the mains power supply with both poles.
Earth/ground connector.
For protection against parasitic currents or voltages, always
connect RMO25T earth/ground connector to protective ground
(PE). Use only the original cable.
For safety reasons, always establish this connection as the first
one before you do any other connections, and separate this
connection as the very last one.
Figure 5-2:
The Language
menu
Figure 5-1:
The Settings menu
9
RMO25T Getting Started
Move the cursor to the position of your choice using the LEFT/RIGHT buttons, and change the value with
the ENTER button.
Pressing ENTER to confirm, returns you to the Main menu.
Pressing STOP to cancel, returns you to the Main menu.
Figure 5-3:
The Time menu showing
RMO25T time
and date
10
RMO25T Getting Started
6 Getting Started
6.1 Current test
Connecting a Test Object to the RMO25T
Before you connect a test object to RMO25T, make sure that:
The test object is disconnected or separated from its circuit in accordance with the national safety
regulations and is properly grounded to protective earth.
RMO25T itself is properly grounded. To do so, connect the grounding screw to PE using a grounding
cable.
One end of measured windings is properly grounded. An only exception is the case when YN
connection is tested and Neutral and Earth bonds are connected between each other. Only in this
case one side of the measurement circuit must not be earthed because it is not necessary and it will
affect the RMO25T reading incorrectly.
See example of a two channel setup in the figure below (6-1).
C A U T I O N
FOR SAFETY REASONS, ALWAYS ESTABLISH A CONNECTION OF THE DEVICE WITH
TEST OBJECT IN THE WAY AS DESCRIBED IN THE FIGURE 6-1.
DO NOT CONNECT MEASURING CABLES AFTER TEST STARTS.
DO NOT DISCONNECT ANY LEADS BEFORE THE LED DISCHARGE AND THE BUZZER
ARE OFF.
The Figure 6-2 shows simultaneous testing of both windings (high and low) on a single-phase
transformer. In such a way, it is possible to speed up the measurement when two channels are used to
test both windings of the transformer.
When performing a two channel measurement; connect the Current connection cable as in the
example below (Figure 6-2.) and outside the Sense leads.
Figure 6-1:
Connecting a test
object to RMO25T
With RMO25T turned off, connect RMO25T to
the test object in such a way that the measuring
cables from the "Voltage Sense" sockets are
attached as close as possible to RX, and in
between the current feeding cables. That way,
resistance of both cables and clamps is almost
completely excluded from the resistance
measurement. Pay attention to polarity while
connecting measuring cables.
To maximize accuracy and measurement
repeatability; make sure that all clamps have a
good connection to the test object and avoid
any connection between Sense and Current
clamps.
11
RMO25T Getting Started
Testing of a Delta-delta winding resistance is usually a very time consuming procedure. This is because
the two windings resemble two closed loop inductors. When energy is brought into the inductors, this
energy (in the form of D.C. current) continually circulates within each winding. A method to quickly test
this configuration requires that both the high side and low side are connected in series with the Winding
Ohmmeter. By having these two windings in opposing polarity, the internal circulating currents settle very
quickly to obtain a balance, and discharge with the same speed. Even if only one side of the transformer
needs to be tested, connecting both high and low windings in series will speed up the test considerably.
On/Off
Connect the earth/ground lead first before doing any connections to the test object.
Connect the mains lead to a mains outlet 100 V 240 V AC and turn on RMO25T with the power
switch on the back of the test set. The first shown on the display is the name of the product followed
by the instrument model type and the internal firmware version.
Figure 6-2:
Connecting a test
object to RMO25T
Figure 6-3:
Connecting a test
object to RMO25T
12
RMO25T Getting Started
Setting the Measurement Parameters
Directly after the first display RMO25T automatically changes to the Current menu and the
green LED lights up.
Before a test can be started, the following needs to be defined in the Current menu:
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, 25 A.
Memory position, 00-499
Maximal test duration time can be set between 10 minutes and 120 minutes depending on
the test current, see table under Measurement parameters(section 6).
In the Current menu, define a test current for the test (here 500 mA). To do so, set the value of your
choice by means of the UP/DOWN buttons. Define the test duration time and then the memory position
(here MEMORY:123).
Using button RIGHT move the cursor to the memory location position, and using UP/DOWN select desired
memory position to which obtained results would be saved. Once the test is completed (either due to
time expiration or when pushing the STOP button) the last measured result will remain registered in
RMO25T, and the memory position is automatically switched over to the next memory position. The
result can be recalled later by selecting that particular position number.
Using RIGHT button move the cursor to the test duration position, and using UP/DOWN buttons select
desired value.
Measuring with RMO25T
Before a test can be started, test current, memory position and the test duration time need to be defined
using the Current menu.
Once these parameters are defined, press ENTER to change to the Ready state.
The Ready state displays the selected test current and its duration is defined. If one of these values has
to be changed, press STOP to return to the Current menu.
The flashing green LED indicates that RMO25T is now ready to start the test. Press the START
button to run a test. At the start of the test, a cable connection check is done. In case of e.g. a
disconnection, an alarm is activated and the error message is shown on the display.
Figure 6-4:
The Curr menu
Test current
Memory position
Test duration time
Menu name
Figure 6-5:
The Ready state
before the test
Memory
Time and Date
13
RMO25T Getting Started
During the test, both the green and the red LEDs flash alternately and the buzzer beeps. When the
current is stabilized, RMO25T starts the measurement of the test object resistance.
The display shows test current (here 498 mA) and the effective value of the measured resistance (here
567,2 mΩ on channel 1 and 567,3 mΩ on channel 2). The time remained until the end of test procedure is
also shown on the display (here 119 min and 49 sec).
Test could be completed in two ways:
- Pushing the STOP button,
- Automatically after the selected time has expired.
When the test is finished either because selected time has expired or the STOP button is pressed,
the RMO25T switches to the Results menu and starts current discharging process. During current
discharging, the discharging LED lights and the alarm beeps.
Discharge is completed when LED discharge and the buzzer are OFF. Also, during that period
Discharging ing discharging process it is not possible to
start another measurement.
Once the test is completed the last measured result will remain registered at a selected memory location
(00-499 memory locations).
Discharge Current
The voltage at the RMO25T output generation is immediately stopped, but current still flows, because of
the inductivity of test objects.
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 transformer that is under test. Never remove the
leads during the testing process and always allow enough time for the transformer being tested to
completely discharge. Large transformers can require several minutes to discharge.
C A U T I O N
DO NOT DISCONNECT LEADS BEFORE “DISCHARGING” MESSAGE IS DISAPPEARED
FROM THE DISPLAY AND THE DISCHARGING DIODE IS OFF.
Figure 6-6:
The Curr menu
during the test
Figure 6-7:
The Res menu
showing the test results
Memory
14
RMO25T Getting Started
Note: Using DV-Win the results could be stored to a PC, where reading interval results is adjustable.
Results will be shown in a table in Excel format with an option to perform additional edit and
graphic presentation.
Using DV-Win after the test in order to transfer the results from selected internal memory location
to a PC will allow transfer of the last test result only.
Measurement parameters
Typical accuracy given below is valid if the maximum possible current is used.
Range
Test
Current
Nominal
Resistance
Full Range
Display
Resolution
1
25 A
1
2
25 A
3
25 A
4
25 A
5
25 A
6
25 A
7
15 A
8
10 A
9
5 A
10
2 A
1
11
1 A
12
500 mA
13
100 mA
14
50 mA
15
10 mA
16
5 mA
The highest resolution of the reading is always displayed; resistance range selection is performed
automatically and therefore is not necessary to be set by the operator.
Accuracy
Typical accuracy of RMO25T is ±(0,2 % rdg + 0,2 % FS). This accuracy is valid if the maximum possible
current is used. Always try to use as high current as possible, but to avoid the risk of heating the winding,
it is recommended not to exceed from 10 % to 15 % of the nominal current of transformer. It is important
to get a good connection between clamps and the connecting point on the test object to achieve stable
and accurate test results. Guaranteed accuracy is ±(0,4 % rdg + 0,4 % FS).
Viewing the Test Results
Once a test is finished, RMO25T automatically changes to the Res menu to display the test results.
Figure 6-8:
The Res menu
showing the test
results
Test current
Memory position that holds the results
Measured resistances of the test objects
15
RMO25T Getting Started
6.2 Tap Changer test
Using RMO25T Tap Changer (TapC) menu the winding resistance of individual taps of a power
.Also it can be used to control the transformer tap changer.
This is a user friendly way of winding resistance measurement and tap changer control, since automatic
measurement is possible with no need to remove the current between each tap change. During
switching the inputs of the instrument are protected to avoid damage that could occur should a tap
changer prove to be faulty while testing.
From the Current outputs, RMO25T injects a constant current into the power transformer. From this
current value and the voltage measured, the winding resistance is calculated. An interruption caused by
a defective tap changer results in a comparatively high measured values of current ripple.
Setting the Measurement Parameters
Turn on RMO25T with the power switch on the back of the test set. The display shows the
Current menu and the green LED lights up. Press button LEFT and using UP button go to the
TapC menu.
In the TapC menu, define a test current for the test (here 10A). The following values can be
chosen: 1 A, 2 A, 5 A, 10 A, 15 A.
To do so, set the value of your choice by means of the UP/DOWN buttons. In the TapC menu of
RMO25T, current output value is rated continuously at 20 A or less. Define the memory position (here
MEMORY:123). Using button RIGHT move the cursor to the memory location position, then using
UP/DOWN select desired memory position to which obtained results would be saved.
By pushing the Ωbutton, resistance and current ripple measured results will remain registered in internal
memory of RMO25T, and the memory position is automatically switched over to the next memory
position. These results can be recalled later by selecting that position number.
Note: Only Ch:1 (left channel) is active channel.
Figure 6-9:
Connecting a test
object to RMO25T
and DV-Win
Figure 6-10:
The TapC
menu
Test current
Memory position
Menu name
Active channel
Time and Date
16
RMO25T Getting Started
Tap Changer test with RMO25T
Before a test can be started, test current and memory position need to be defined using the TapC menu.
Once these parameters are defined, press ENTER to change to the Ready state.
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.
The flashing green LED indicates that RMO25T is now ready to start the test. Press the START
button to run a test. At the start of the test, a cable connection check is done. In case of e.g. a
disconnection, an 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, buzzer
beeps .
When the current is stabilized, the device shows test current (here 9,98 A) and the value of the measured
resistance (here 567,2 mΩ).
At the moment the resistance result is stable, press the OMEGA button to save the resistance result of
the Tap Changer starting position. The memory position is automatically switched over to the next one
and device is ready to record the current ripple.
During saving the resistance the red LED flashes shortly and beeper sound is speeded up.
Change the Tap Changer position to the next tap by pushing the "Up" or "Down" button of the tap
changer control. Because the resistance is changed, current will be unstable and RMO25T will sample
and hold the largest measured current ripple that occurred in the actual measuring cycle. It is indicated
as a RIPPLE (%) with reference to the test current.
The display shows the value of the test current in new tap position (here 9,82 A), and the value of the
current ripple occurred during the change from previous position to the new one (here 4,7 %). At the
moment the test current shown on the display is stable, the RMO25T shows the resistance value in new
tap position (here 569,8 mΩ). Press the OMEGA button to save the resistance and the ripple in the new
position of Tap Changer.
Figure 6-11:
The Ready state
before the test
Figure 6-14:
The TapC menu,
memory position is
increased for one
Figure 6-12:
The TapC
menu when the test
current is stabilized
Figure 6-13:
The TapC menu,
change the tap
position
17
RMO25T Getting Started
Repeat this procedure as often as needed until the results for RIPPLE and RESISTANCE are obtained
for all Tap Changer positions.
Test is completed pushing the STOP button.
When measurement is completed (after pressing the STOP button) RMO25T switches to the TapC
menu and starts current discharging. During the current discharging process, the discharging LED
lights and alarms beeps.
Discharge is completed when LED discharge and the buzzer are OFF. Also, during that period
start another measurement.
A properly working tap changer differs from malfunctioning one in a current discontinuity during the tap
change, by the magnitude of the current ripple value. A discontinuity will result in much higher current
ripple value (99 % or 100 %) than a properly functioning tap changer.
Note: Current ripple value depends on the construction of the tap changer. It is recommended to
compare current ripple values between each other got on one transformer. Also, it is
recommended to compare current ripple results on one transformer with results from some
previous test in order to follow conditions of that tap changer.
Figure 6-17 shows indication about possible tap changer bad conditions during the change from tap to
tap.
e shown on
the display, red LED will light and buzzer will beep continuously. Discharging process starts.
Discharge Current
The voltage at the RMO25T output generation is immediately stopped, but current still flows, because of
the inductivity of test objects.
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 transformer that is under test. Never remove the
leads during the testing process and always allow enough time for the transformer being tested to
completely discharge. Large transformers can require several minutes to discharge.
Figure 6-16:
The TapC menu during
discharging
Figure 6-17:
The TapC menu
showing much higher
current ripple value
Figure 6-18:
Message
"Discontinuity"
18
RMO25T Getting Started
C A U T I O N
DO NOT DISCONNECT LEADS BEFORE “DISCHARGING” MESSAGE IS DISAPPEARED
FROM THE DISPLAY AND THE DISCHARGING DIODE AND BUZZER ARE OFF.
Note: Using DV-Win the results could be stored to a PC, where reading interval results is adjustable.
Results will be shown in a table in Excel format with an option to perform additional edit and
graphic presentation.
Using DV-Win after the test in order to transfer the results from selected internal memory location
to a PC will allow transfer of the last test result only.
Using DV-Win software it is possible to draw a graph which represent dynamic resistance during the
change from tap to tap (refer to section 7.6).
Tap Changer Remote
The external Tap Changer Remote cable is used for convenient tap changer testing.
After the RMO25T has measured a tap it stands by waiting for the operator to move the transformer tap
changer to the next tap position and continue the measurement by pressing OMEGA button on the unit.
The tap changer operation box on power transformers is normally not placed at the same place where
the RMO25T is placed. The Tap Changer Remote block allows the operator to continue the next tap
measurement from the RMO25T position. It is performed by pressing UP/DOWN buttons on the Tap
Changer Remote block.
The operator has to connect the Tap Changer Remote cable from the RMO25T to the tap changer
operation box. An example of that connection is shown on the figure below.
When the appropriate connection is done, the operator has possibility to press REMOTE button on the
RMO25T device to control the tap changer from the RMO25T, or to press LOCAL button to control the
tap changer from the tap changer operation box.
Relays which are built-in
inside the RMO25T
Brown
White
Yellow
Green
Tap Changer
Remote Cable
19
RMO25T Getting Started
6.3 Viewing Results of Previous Tests
RMO25T stores up to 500 test results. They can be viewed using the Memory menu at memory
positions from 0 to 499.
Go to Memory menu using SET button.
Selecting a memory position on the Memory menu displays:
,
,
R1 (left channel/channel 1) or R2 (right channel/channel 2),
RESISTANCE and RIPPLE,
and the time, of this particular test.
6.4 Deleting Results of Previous Tests
In the Memory menu, press ENTER.
Press ENTER once more to delete saved measurements from all the memory positions. Press STOP to
leave the Memory menu without deleting any measurements.
6.5 Printing the Test Results
RMO25T stores up to 500 test results. They can be printed using the Print menu at memory positions
0 ... 499.
Go to Print menu pressing RIGH button repeatedly from Current menu as well as from TapC menu.
Select first and last memory position with the UP/DOWN buttons and press ENTER button. The results
that are located in the range between these memory locations, including the chosen memory locations,
will be printed.
Figure 6-19:
The Memory menu
showing the previously
saved test results
measured in Curr
mode saved in memory
position 123
Figure 6-21: The Memory
menu showing an option to
delete all saved
measurements from the
memory positions
Figure 6-20:
The Memory menu
showing the previously
saved test results
measured in TapC
mode saved in memory
position 124
Figure 6-22: The
Memory menu showing
no results
20
RMO25T Getting Started
Settings of the printer as well as look of the RMO25T Test Report are given at figure above.
6.6 Duty Cycles
During tests, RMO25T generates a high DC current that heats up the test set. To prevent RMO25T from
overheating, certain duty cycles apply depending on the test current used.
Cooling time between two measurements is proportional to test duration time.A built-in control prevents
skipping these cooling times. If you try to start a test within the cooling period, the display shows "Wait"
and a timer counting down. After the cooling period has passed, start a new test using the set test
parameters by pressing the START button.
C u r r e n t T e s t
Test current
(A)
Maximal test
duration time (min)
Cooling time for
maximal test
duration time (min)
5 mA, 10 mA, 50 mA,
100 mA, 500 mA, 1 A,
2 A, 5 A, 10 A
120
0
15 A
90
5
25 A
50
5
Figure 6-23:
The Print menu showing
first and last memory
position and Date and
Time of printing
Table 6-24:
Cooling time
between current
tests
Table of contents
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