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HVDC TRANSFORMER BUSHINGS
PHI 530.1425.2500
PHI 265.850.1500
Kepco project
IS 2664 GB
Page
18
of
70
6.1 Oil pressure vs average temperature
PHI bushings are sealed and pressurized devices. To compensate the oil volume variation by the temperature,
each unit is provided with a built-in expansion vessel system equipped with internal bellows (Prysmian expansion
vessel).
This expansion system allows to maintain a positive pressure at the minimum expected oil temperature,
generally equal to the minimum specified ambient temperature, and the maximum oil expansion volume related
to the oil maximum average temperature during the bushing operation.
On the basis of the above-mentioned design concepts and the specific technical characteristic of the selected
expansion vessels, the next
Figure 8
shows the curves Pressure vs Average oil temperature for the two PHI
bushings.
Figure 8 – Oil pressure vs. average oil temperature
This curve is used in GE Factory to set the proper oil pressure at the end of the bushing production process and
it is also useful to check the bushing status during the operation by controlling the oil pressure on the built-in oil
pressure gauge, see next
Paragraph 6.2
.
6.2 Oil pressure gauge
To monitor the pressure important parameter each unit is provided by one or more pressure gauges, provided
with electrical contacts (see
Figure 9
).
The events that can be detected by this pressure gauge are:
•
Low oil pressure, related to the possibility of an oil leakage from the oil impregnated paper section.
•
High oil pressure, related to an internal fault in the oil impregnated paper section or a gas leakage from
the gas section of the bushing.
Содержание PHI 265.850.1500
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