► In order to remove air bubbles under the bushing flange, open the air release screw flange
(3) so that the air can escape (partial unscrewing of the screw will suffice).
The screw (2) serves to fill the bushing with dry filling. It must never be opened.
► In order to vent the central tube, open the air release screw head (1) (partial unscrewing of
the screw will suffice).
► After venting, tighten all the opened air release screws again.
6.3
Check bushing
► Check the status of the bushing before commissioning.
6.3.1 Visual inspection
► Check the visible parts of the bushing for damage visually.
► Make sure that all screw connections are tightened in accordance with the stipulations
on page 52).
► Make sure that the removable cap on the test tab is screwed on tightly.
6.3.2 Leak test (visual)
The leak testing of the installed bushing can only be carried out to a limited extent.
Transformer oil is not present at all positions on the bushing. The oil is present at the flange,
it is adequate for vertically-installed bushings, but does not always reach to the head.
► Check whether and where oil is coming out of the bushing.
6.3.3 Electrical testing
All bushings are tested in final acceptance tests and are tested suitable for
operation.
The electrical measurements include:
● Bushing capacitance as main capacitance C
1
● Power factor of main capacitance tan δ
The capacity C
2
between the last grading layer and the flange, and the power
factor tan δ of C
2
can be measured. However, they do not facilitate any statement
concerning the main insulation, and simply indicate the status of the test tab area
and will be influenced by ambient influences (scatter capacity).
Range STARIS®-Sia+
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