11
1ZSE 5492-115 en, Rev. 5
1.3 Oil
The oil quality should be IEC 60296-LCSET -30° (former Class II). The oil should have an
electrical withstand of at least 40 kV, measured in a 2.5 mm gap, according to IEC 60156.
New oil should have a water content below 15 ppm and have been handled and stored ac-
cording to IEC 60422 point 10.
Table 1. Weight of oil in kg.
Type designation
UZE.N, UZE.T
OLTC with separate
conservator
1)
OLTC with expansion volume
in the tank
200/... 500 450
250/... 500 450
380/... 950 880
550/... 1250 1150
650/... 1250 1150
Type designation
UZF.N, UZF.T
OLTC with separate
conservator
1)
OLTC with expansion volume
in the tank
200/... 400 430
250/... 400 430
380/... 750 800
550/... 1050 1120
650/... 1050 1120
1) The oil for the conservator is not included.
WARNING
Do not energize the transformer until oil has been lled as per chapter 6, Oil Filling, in
this guide.
1.4 Oil conservator
The on-load tap-changer has to be connected to an oil conservator, except when it is an
UZE with expansion volume in the tank. ABB recommends the use of a separate conserva-
tor for the on-load tap-changer with both oil and air side separated from the main conserva-
tor of the transformer.
The volume of the conservator should be such that there is oil left in the conservator even at
the lowest oil temperature expected and such that no ooding can occur at the highest oil
temperature expected.
A suitable dimension of the tube for connection to the conservator is an inner diameter of
approximately 20 mm. The tube should be inclined at least 3 degrees to avoid gas cushions
in the tube. A valve in the connection to the conservator is recommended.
The conservator must be equipped with a breathing device that does not allow moist air into
the conservator and that allows the gas from the arcs to disappear. We recommend that the
breather for the tap-changer should be bigger than normally used for that amount of oil, as
the tap-changer is breathing more frequently because of the gas produced at each tap-
changer operation.
The conservator should also be equipped with an oil level indicator, and an alarm contact for
low oil level is recommended.
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