13
RMO10T Getting Started
Accuracy
Typical accuracy of RMO10T 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, RMO10T automatically changes to the
Res
menu to display the test results.
6.2 Tap Changer test
Using RMO10T’s Tap Changer (TapC) menu the winding resistance of individual taps of a power
transformer’s tap changer can be measured.
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 during testing.
From the current outputs, RMO10T injects a constant current into the power transformer. From this
current value and the voltage measured, the winding resistance is calculated. A discontinuity caused by
a defective tap changer results in a comparatively high measured values of current ripple.
Setting the Measurement Parameters
Turn on RMO10T with the power switch on the back of the test set. The display shows the
Curr
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: 1A,
2A, 5A, 10A.
Figure 6-8:
The
Res
menu
showing the test
results
Test current
Memory position that holds
the results
Measured resistances of the test objects
Figure 6-9:
Connecting a test
object to RMO10T
and RMOWin-T2M
Figure 6-10:
The
TapC
menu
Test current
Memory position
Time
Menu name
Active channel
