24
1ZSE 5492-129 en, Rev. 6
WARNING
Be aware of the risk for slipperiness caused by oil spillage for instance when working
on the transformer cover.
1.
Lower the oil level of the transformer to just below the cover. For information about oil
draining, refer to the transformer documentation.
2.
Operate the on-load tap-changer electrically one step and let it stop in service position.
Note the service position of the on-load tap-changer.
3.
Operate the motor-drive by hand cranking the few degrees needed to position it in its
exact position as given in section ”Disc brake” in the appropriate Maintenance guide.
4.
Lock the motor-drive mechanism with the locking device delivered with the unit.
5.
Remove the cover of the gear box to be replaced. If the on-load tap-changer consists
of more than one unit driven by the same motor-drive, remove the covers of all the gear
boxes.
CAUTION
The gear boxes, and the transformer when the gear box is removed, must be protected
from water. If there is the slightest risk for rain or snow, some kind of protection must be ar-
ranged.
6. Check that all units are in their exact position acc. to Fig. 8. The opening in the brass
toothed wheel should face the red point in the gear box housing exactly in all units.
Max permitted deviation is shown in Fig. 8.
Also check that all units are in the same service position as the motor-drive.
If something is out of range, please consult ABB for advisory.
CAUTION
To take an on-load tap-changer that is not aligned and/or out of position into service means
a great risk for damaging both the on-load tap-changer and the transformer.
It is very important that the following instructions are followed in detail to make sure that the
on-load tap-changer will be properly lined up after the repair.
If gear boxes on more than one unit on an on-load tap-changer with two or three units
driven by the same motor-drive are to be replaced, replace one at the time as described
below. Start with the one closest to the motor-drive.
7.
Loosen the hose clamps on the protection tubes on the shaft/shafts to be removed.
Push the tubes together to get access to the couplings.
CAUTION
Note in which direction the gear box is mounted to ensure correct mounting of the new one.
8.
For UCL:
Unscrew the four screws (M10, cylindrical head with hexagon socket 8 mm)
holding the gear box, see Fig. 8. These screws are locked with locking fluid and need
considerably high loosing torque.
For UCG, UCC, UCD: Unscrew the four screws M10 for the four clamps that hold the
gear box.
9. If there are two shafts, loosen the screws of one of the brass couplings on the shaft
closest to the motor-drive. Lift out the gear box and take care of the shaft/shafts when
it/they comes/come loose from the gear box. If there are two shafts, note which sides
they belong to.
3. Repairs and adjustment
