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HVDC TRANSFORMER BUSHINGS
PHI 530.1425.2500
PHI 265.850.1500
Kepco project
IS 2664 GB
Page
19
of
70
Figure 9 – Oil pressure gauge
Each instrument is equipped with 4 Normally Open micro-switches that provide alarm / tripping signals.
Table
10
shows the micro switches purpose and the pressure set up.
Micro switch
Description
Pressure set up
[bar gauge]
[MPa gauge]
Low pressure
Tripping
Too low pressure for operation
0.2
0.02
Low pressure
Alarm
Low pressure related to low oil
level
0.4
0.04
High pressure
Alarm
Overpressure inside the OIP
section
2.6
0.26
High pressure
Tripping
Too high pressure inside the
OIP section for operation
2.8
0.28
Table 10 – Alarm and tripping micro switches set-up
The pressure gauge is installed on a ball type valve for easy replacement in case on need and all electrical
cables are wired in the junction box provided with DIN type terminal blocks (see
Appendix 2
).
Additional information about the oil pressure gauge device are in illustrated in
Appendix 5
.
6.3 PHI Bushing filtering & bypass valves
PHI bushings are equipped with a special valve system located at the level of the central flange that allows:
•
The oil filling under vacuum.
•
The oil recirculation for filtering and the oil passage during the normal operation.
NOTE:
Operation on the valves must be done by qualified and authorized operators only.
Depending on their specific function, they are named filtering and by-pass valves (see
Figure 10
). These valves
are installed inside some metallic protrusions on the bushing flange, protected by metal lids (see
Figure 11
).
The number of valve blocks is related to the size of the bushing.