15
RMO30T Getting Started
button to start resistance measurement in the new position of Tap Changer. New resistance value is
displayed (here
719,3m
Ω
).
The memory position is automatically switched over to the next memory position. Repeat this procedure
as often as needed until the results for
Δ
and R are obtained for all Tap Changer positions.
Test is completed pushing the
STOP
button.
The voltage at the RMO30T output generation is immediately stopped, but current still flows,
because of the inductivity of test objects.
When measurement is completed (after pressing the
STOP
button) RMO30T 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
“Discharging” message is shown on the display. During discharging process it is not possible to
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.
If current circuit is opened during the change from tap to tap, message „Discontinuity“ will be shown on
the display, red LED will light and buzzer will beep continuously. Discharging process starts.
Discharge Current
The voltage at the RMO30T 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.
Figure 6-16:
The
TapC
menu during
discharging
Figure 6-15:
The
TapC
menu
during the test
Figure 6-17:
The
TapC
menu
showing much higher
current ripple value
Figure 6-18:
Message
"Discontinuity"
