27
1ZSE 5492-129 en, Rev. 6
3.2 Replacement of diverter switch housing cover gasket
3.2.1 General
This instruction guides you how to attend to an oil leakage. The instruction can be used for
all UC-types of on-load tap-changers.
3.2.2 Tools required
■
Box wrench (19 mm)
3.2.3 Material and spare parts required
■
O-ring (8 mm), for UCG 428 x 8, and for UCL 540 x 8
O-ring, for UCD and UCC, 806 x 10
■
Grease (as for ball-bearings), (see 3.1.3)
3.2.4 Procedure
WARNING
Before any work is carried out on the on-load tap-changer:
Make sure that the transformer is disconnected and that earthing is properly carried
out. Obtain a signed certificate from the engineer in charge.
Be aware of the risk for slipperiness caused by oil spillage for instance when working
on the transformer cover.
The oil in the diverter switch housing may be hot. Be cautious!
There is always a cushion of explosive gases in the top of the diverter switch housing.
No open fire, hot surfaces or sparks may be present during opening of the housing
or draining from the valve. After the cover is removed let the gas vent away approxi-
mately 15 min before any work is started.
CAUTION
Protect the on-load tap-changer from water.
1.
Retighten the nuts that hold the cover.
If the oil leakage still remains, the O-ring has to be replaced.
2.
Shut the valve to the oil conservator.
3. Remove the cover. If the oil level is less than 50 mm below the cover, point 6 should be
carried out before energizing.
4.
Replace the O-ring with a new one. Clean the slot and the corresponding part of the
cover. The O-ring is not to be glued.
5. Mount the cover. Turn the cover so the guiding pin in the housing is facing the guiding
hole in the cover. (The cover has to be pressed down in order to overcome the spring
force of the springs that hold the diverter switch in place). Tighten the nuts alternately.
Tightening torque 42 Nm.
6. Restore the gas cushion, if necessary, according to section 3.3 in this guide.
7.
Open the valve to the oil conservator.
3. Repairs and adjustment
