ABB UZE User Manual

23
1ZSE 5492-115 en, Rev. 5
6. Oil lling
6.1 Filling methods and restrictions
Oil lling can be carried out at atmospheric pressure or under vacuum. The wall between the
on-load tap-changer and the transformer tank is designed to withstand vacuum on one side
and atmospheric pressure on the other side. Having vacuum on one side and the pressure
of an oil column on the other side is not permitted.
UZE can be delivered with an oil expansion volume in top of the tank. The design of UZF
does not allow an oil expansion volume in the tank. Instead, UZF can be delivered with a
built-on oil conservator. See also Figs. 2, 3 and 4.
Oil lling may be carried out in different ways depending on what the transformer manufac-
turer considers convenient, as long as the above rules are complied with and the on-load
tap-changer is lled with oil to the correct level.
The methods below are recommended, and if they are followed in detail no pressure limits
will be exceeded.
6.1.1 Retightening
Before oil lling, the front cover and the connection cover on UZF should be retightened.
Tightening torque 42 Nm. The welded stud bolts should not be over-tightened.
Retighten again after the transformer has been in service for about two weeks, to let the
gaskets settle at service temperature.
6.2 Filling at atmospheric pressure
1. Open the conservator valve, if any.
2. Dismantle the pipe to the breather. Or, if simpler, remove the air relief valve (one way
breather) or the dehydrating breather.
3. Connect the pump to the oil valve on the on-load tap-changer tank. For dimension see
the dimension drawing. Open the valve and pump in oil to the correct level shown on
the oil level indicator. For correct oil level, see section 6.4.
4. Shut the oil valve and disconnect the pump.
5. Reassemble the pipe or the breather. The connections must be airtight; therefore use
sealing tape on the threads and O-rings in the anges.
When the transformer and the on-load tap-changer have a common oil conservator, a lter
in the connection between the on-load tap-changer and the conservator is needed. (For
information see page A10).
1. The conservator valve should be shut.
2. Open the air release valve on the oil lter housing.
3. Connect the pump to the oil valve on the on-load tap-changer tank. Open the valve and
pump in oil. Stop the pump when oil reaches the air release valve.
4. Shut the oil valve and the air release valve and disconnect the pump.
5. Open the conservator valve.
CAUTION
Do not energize the transformer earlier than three hours after oil lling in atmospheric pres-
sure. This waiting period is needed to allow airbubbles to disappear.
6 Oil lling

ABB UZE Specifications

General

Brand	ABB
Model	UZE
Category	Industrial Equipment
Language	English