ABB BUL2 Wartungshandbuch - Seite 13
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3. Overhaul
WARNING
Before any work is carried out on the tap-changer:
Make sure that the transformer is disconnected and
that grounding is properly carried out. Obtain a signed
certificate from the engineer in charge.
3.1 Required tools and materials
Necessary for the overhaul is the following equipment:
– Normal hand tools (wrench sizes up to 19 mm)
– Standard set of combination wrenches
– Sliding caliper
– Spring balance (10 N)
– Grease (GULF-718 EP synthetic grease, Mobilgrease 28,
Shell-Aero Shell grease 22 or similar
– Oil (for plain ball and roller bearings)
The motor-drive mechanism should normally be regularly
overhauled at intervals of 300,000 operations. The number
of operations must not exceed 1,500,000, which is the
mechanical lifetime of the motor-drive mechanism.
It is recommended to perform the overhaul of the motor-drive
mechanism and the other parts of the tap-changer at the
same time. See the appropriate maintenance guide for the
tap-changer.
The overhaul includes the following points:
Before disconnecting the power supply:
– Motor protection function (Section 3.2)
– Ground fault protector (option) (Section 3.3)
– Counter function (Section 3.4)
After disconnecting the power supply:
– Heater function (Section 3.5)
– Toothed belt (Section 3.6)
– Cable connections (Section 3.7)
– Disc brake function (Section 3.8.1 for BUE; Section 3.9.1
for BUL2)
– Position transmitter and other position switches
(Section 3.8.3 for BUE; Section 3.9.2 for BUL2)
– Lubrication (Section 3.8.4 for BUE; Section 3.9.3 for BUL2)
Reconnect the power supply and carry out operation tests
according to the instructions in the tap-changer installation
guide.
3.2 Motor protection
WARNING
The motor power voltage is dangerous.
The function of the protective motor switch is checked. For
three-phase AC motors, one of the phase fuses is removed
and the function time of the protective motor switch is
checked by a RAISE or LOWER operation. The protective
motor switch shall release within 60 seconds at a current
setting equal to the rated current of the motor at actual
voltage.
If the protective motor switch does not trip within 60 seconds,
switch off the power and adjust the current setting. Repeat
the test when the motor is cold.
Protective motor switches for DC motors and for single-phase
AC motors are not tested.
3.3 Ground fault protector (option)
If the motor-drive mechanism is equipped with an outlet, the
ground fault protector should be tested by pressing the test
knob on the outlet.
3.4 Counter
Check that the counter is functioning for RAISE and LOWER
operations.
Check that the position indicator increases (decreases) one
step and the counter advances one step for each operation.
Record the counter's value. The counter shows the number of
operations run by the tap-changer.
3.5 Heater
WARNING
Before starting any work inside the motor-drive
mechanism, the auxiliary power must be switched off.
N. B. The motor, contactors and heating element may
be energized from separate sources.
Check by feeling with a finger that the elements have been
functioning.
1ZSC000498-ABH en, Rev. 1 | Maintenance guide BUE/BUL2 13