
44
Technical guide VUC
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1ZSC000562-AAX en, Rev. 1
Oil conservator
Although tap-changers of the vacuum type produce very small
amount of gases, and far less particles than non-vacuum
types, it is still recommended to use separate conservators
in order to avoid possible impact on transformer DGA and
particles coming into the transformer. The transformer
manufacturer must provide a conservator for the tap-changer.
The diverter switch housing needs to be connected to an oil
conservator. Consider the below as a guideline for the design
of the tap-changer oil conservator.
1. The breathing device should prevent moisture from getting
into the tap-changer compartment and let gases out.
2. The oil volume should be such that the oil level always is
within the range of the oil level indicator at all predictable
temperatures.
It is recommended to have the size of the conservator for
vacuum type tap-changers an additional 15 l to the normal
design rules of a tap-changer conservator. In order to have
enough oil in the conservator to allow oil samples to be
taken until the first maintenance stop without filling up with
new oil.
3. It is recommended to install the oil sampling valve with
piping accessible from ground level so that oil samples
can be taken without disconnecting the transformer.
4. X corresponds to a height giving a max recommended
pressure difference between the tap-changer diverter
switch housing and the transformer tank of 50 kPa.
5. H corresponds to a height giving a max pressure
difference between the tap-changer diverter switch
housing and the atmosphere of 70 kPa. For higher
pressure difference, contact ABB for advice.
6. The oil level for the tap-changer should be equal or below
the oil level of the transformer. Temporary during service
the value is allowed to be negative.
7. A vacuum proof conservator is needed if the tap-changer
should be oil filled under vacuum with the conservator
mounted.
No special considerations is needed for transformer
installations at high altitude.
Note that separate oil conservators for the transformer
and the tap-changer are recommended. Both oil and air
side should be separated. For transformers with common
conservator for both the transformer and the tap-changer a
filter should be mounted in the pipe from the tap-changer to
the conservator.
Fig. 59.