Winding Ohmmeter RMO-TW

 Three resistance measurement channels

 One temperature measurement channel
 Accuracy 0,1 %
 Lightweight
 On-load tap changer verification
 Automatic resistance measurement for the Heat Run test
 Automatic discharge circuit
 Four models: RMO10TW, RMO20TW, RMO30TW, RMO50TW

Description
The Winding Ohmmeter of the RMO-TW series RMO-TW instrument can perform a simple,
is designed for winding resistance measurement quick and reliable transformer on-load tap
of inductive objects. The RMO-TW instrument is changer verification. This instrument enables
based on the state of the art technology, using measurements of a winding resistance in every
the most advanced switch mode technology tap position of an on-load tap changer without
available today. The RMO-TW instrument is discharging between the tests. Problems with
accurate (0,1%), powerful (up to 50 A) and switching of the OLTC, such as interruption, can
lightweight. It generates a true DC ripple free be detected with these measurements.
current with automatically regulated
measurement and discharging circuit.

Application
The list of the instrument application includes:

 Three-channel winding resistance measurement, which enables simultaneous winding resistance

measurement of up to three windings on a single phase
 Detection of interruptions during the operation of on-load tap changers (OLTC), performed on a
single phase

 Heat Run test, which enables obtaining the Hot Spot temperature along with resistance graph during
the cooling process
B-RXX0TW-303-EN, 2016-10-25

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 Connecting RMO-TW to Transformer Resistance Testing in Multiple Tap
The RMO-TW has three separate resistance
Changer Positions
measurement channels, which enable The winding resistance of all tap changer
simultaneous measurement of the primary, positions in one phase can be measured as part
secondary and tertiary winding on the same of a single test, without discharging between
phase, as presented in the figure above. This measurements. Different test modes are
significantly speeds up the measurement and provided for on-load tap changers (OLTC) and
reduces the total transformer testing time. At the de-energized tap changers (DETC). The
same time, by saturating the magnetic core instrument detects interruptions during the
through the HV and LV windings the stabilization operation of on-load tap changers and produces
time and subsequently the total testing time is a warning message to the operator.
reduced even more.
DV-Win Software
Simultaneous Three-Channel Winding
The DV-Win application software enables
Resistance Measurement
control and observation of the test process, as
The RMO-TW injects the current with a voltage well as saving and analyzing the results on a
value as high as 55 V. This ensures that the PC. It provides a test report, arranged in a
magnetic core is saturated quickly and duration selectable form as an Excel spreadsheet, PDF,
of the test is as short as possible. The three Word, or ASCII format. The software provides
independent channels enable simultaneous additional OLTC (tap changer) verification
testing of three windings in series – primary, option by recording the test current during the
secondary and tertiary windings. There is transition. The standard interface is USB.
enough memory within the RMO-TW instrument RS232 is optional.
to store 1 000 measurements. All
measurements are time and date stamped.
Heat Run Test Application
The instrument is equipped with thermal and
overcurrent protection. The RMO-TW has very The DV-Win application software has an
high ability to cancel electrostatic and additional Heat Run temperature/resistance
electromagnetic interference that exists in HV extrapolation feature. After the transformer
electric fields. It is achieved by a proprietary heating is switched off, the RMO-TW is
B-RXX0TW-303-EN, 2016-10-25

filtration solution applied to both, the hardware immediately connected to up to three

construction and the application software transformer windings and the timer is started.
implementation. A special mode is provided for The winding resistance is measured at regular
the resistance measurement in multiple de- time intervals. This information is used to
energized tap changer (DETC) positions. automatically extrapolate the values of
temperature and resistance at the moment when
the transformer was switched off.

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 Technical Data Computer Interface
Winding Resistance Measurement  USB
 Test currents:  Optional: RS232
5 mA – 10 A DC for RMO10TW
5 mA – 20 A DC for RMO20TW Warranty
5 mA – 30 A DC for RMO30TW  Three years
5 mA – 50 A DC for RMO50TW
 Output voltage: up to 55 V DC Environmental Conditions
 Measurement range: 0,1 μΩ - 10 kΩ  Operating temperature:
 Typical accuracy: - 10 ºC to + 55 ºC / + 14 ºF to + 131 ºF
±(0,1% rdg + 0,1% F.S.) for 0,1 μΩ-1,999 kΩ range  Storage & transportation:
±(0,2% rdg + 0,1% F.S.) for 2 kΩ - 10 kΩ range - 40 ºC to + 70 ºC / - 40 ºF to + 158 ºF
 Humidity 5 % - 95 % relative humidity,
Resolution non condensing
 0,1 μΩ – 999,9 μΩ: 0,1 μΩ
 1,000 mΩ – 9,999 mΩ: 1 μΩ Dimensions and Weight
 10,00 mΩ – 99,99 mΩ: 10 μΩ Device Weight Dimensions (WxHxD)
 100,0 mΩ – 999,9 mΩ: 0,1 mΩ RMO10TW 7.5 kg / 198 x 255 x 380 mm
RMO20TW 16.5 lbs 7.8 x 10.0 x 15.0 in
 1,000 Ω – 9,999 Ω: 1 mΩ
RMO30TW 8.5 kg / 198 x 255 x 380 mm
 10,00 Ω - 99,99 Ω: 10 mΩ
RMO50TW 18.7 lbs 7.8 x 10.0 x 15.0 in
 100,0 Ω – 999,9 Ω: 0,1 Ω
 1,000 kΩ – 9,999 kΩ: 1 Ω Mains Power Supply
 Connection according to IEC/EN60320-1;
Data Storage
UL498, CSA 22.2
 1 000 internal memory positions
 Mains supply: 90 V - 264 V AC

Printer (optional)  Frequency: 50 / 60 Hz

 Thermal printer  Mains supply voltage fluctuations up to ±10 %

of the nominal voltage
 Paper width 80 mm
 Input power: 2 250 VA
OLTC Dynamic Resistance Measurement  Fuse 15 A / 250 V, type F, not user replaceable
 Sampling rate: 4 ms
Applicable Standards
 Automatic open circuit detection and
warning  Installation/overvoltage: category II

 Transition current ripple measurement  Pollution: degree 2

 Transition time measurement using DV-Win  Low voltage directive: Directive 2014/35/EU
software (CE conform); Applicable standards, for a
class I instrument, pollution degree 2,
 Timing measurement of different transition installation category II: IEC EN61010-1
changes using DV-Win graph analysis tool
 EMC: Directive 2014/30/EU (CE Conform)
B-RXX0TW-303-EN, 2016-10-25

Applicable standard EN 61326-1

 Safety: CAN/CSA-C22.2 No. 61010-1, 2nd

edition, including Amendment 1

All specifications herein are valid at ambient temperature of + 25 °C and recommended accessories.
Specifications are subject to change without notice.
Specifications are valid if the instrument is used with the recommended set of accessories.
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 Current and Sense cables with TTA clamps Voltage Sense cables with TTA clamps

Device bag Cable plastic case

Current connection cable with TTA clamps Cable bag

B-RXX0TW-303-EN, 2016-10-25

Transport case Test shunt

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 Order Info
Instrument with Included accessories Article No
Winding Ohmmeter RMO-TW
DV-Win PC software including USB cable
RMOXXTW-N-00
Mains Power cable
Ground (PE) cable

Recommended Article No
Current cables 2 x 10 m 10 mm2 (32.8 ft, 7 AWG) and Sense cables 2 x 10 m
CS-10-10LMWC
(32.8 ft) with TTA clamps*
Current cables 2 x 10 m 2,5 mm2 (32.8 ft, 13 AWG) and Sense cables 2 x 10
CS-10-02BPWC
m (32.8 ft) with TTA clamps**
Sense cables 2 x 10 m (32.8 ft) with TTA clamps S2-10-02BPWC
Current connection cable 1 x 5 m 10 mm2 (16.4 ft, 7 AWG) with TTA clamps* CX-05-102XWC
Current connection cable 1 x 5 m 6 mm2 (16.4 ft, 9 AWG) with TTA clamps** CX-05-062XWC
Transport case HARD-CASE-ME
*Recommended for RMO30TW and RMO50TW
** Recommended for RMO10TW and RMO20TW

Optional Article No
Test shunt 150 A / 150 mV SHUNT-150-MK
Thermal printer 80 mm (3.15 in) (built-in) PRINT-080-00
Cable plastic case – small size CABLE-CAS-01
Cable plastic case – medium size CABLE-CAS-02
Cable bag CABLE-BAG-00
Current cables 2 x 15 m 10 mm2 (49.2 ft, 7 AWG) and Sense cables 2 x 15 m
CS-15-10LMXC
(49.2 ft) with TTA clamps
Current cables 2 x 15 m 2,5 mm2 (49.2 ft, 13 AWG) and Sense cables 2 x 15
CS-15-02BPWC
m (49.2 ft) with TTA clamps
Current cables 2 x 20 m 16 mm2 (65.6 ft, 5 AWG) and Sense cables 2 x 20 m
CS-20-10LMXC
(65.6 ft) with TTA clamps
Current cables 2 x 20 m 2,5 mm2 (65.6 ft, 13 AWG) and Sense cables 2 x 20
CS-20-02BPWC
m (65.6 ft) with TTA clamps
Sense cables 2 x 15 m (49.2 ft) with TTA clamps S2-15-02BPWC
Sense cables 2 x 20 m (65.6 ft) with TTA clamps S2-20-02BPWC
Current connection cable 1 x 12 m 10 mm2 (39.4 ft, 5 AWG) with TTA clamps CX-12-102XWC
Current connection cable 1 x 12m 6 mm2 (39.4.4 ft, 9 AWG) with TTA clamps CX-12-062XWC
PT100 temperature indicator TI-000-PT100
B-RXX0TW-303-EN, 2016-10-25

IBEKO Power AB Contact

Stockholmsvägen 18 Phone: +46 70 0925 000
181 50 Lidingö, Sweden E-mail: sales@dv-power.com