ABB UZE - During drying of the transformer; Mounting of gaskets; During oil filling

WARNING
The motor-drive mechanism must not be installed in any explosive atmosphere. The
electrical equipment creates sparks which can cause an explosion.
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 certicate from the engineer in charge.
Before starting any work in the on-load tap-changer the protective motor switch and
the LOCAL/REMOTE switch must be set at ”0”.
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.
During drying of the transformer
CAUTION
The on-load tap-changer must not be included in the vapour phase drying process of the
transformer. For permissible pressure and temperature at the rear during drying process, see
chapter 3.
Mounting of gaskets
CAUTION
Sealing surfaces and gaskets must be clean and undamaged. Diametrically opposed bolts
in sealing joints must be tightened alternately several times, beginning with a low tighten-
ing torque and nally with the recommended tightening torque as described in section 1.7
Tightening Torque, in this guide.
During oil lling
WARNING
When oil that has been used in a selector switch compartment is pumped out, con-
ducting tubes and hoses that are earthed should be used to avoid the risk of explo-
sion due to the gases produced by the arcs during service.
CAUTION
Do not ll oil into the on-load tap-changer if the transformer tank is under vacuum and the
on-load tap-changer is not.
Do not ll oil into the transformer tank if the on-load tap-changer is under vacuum and the
transformer tank is not.
The oil level in the oil conservator of the on-load tap-changer should never be above the oil
level in the oil conservator of the transformer.