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Next Figure 13 shows an example of turret arrangement during the treatment operation and relevant oil flows
that can be realized by this arrangement.
Connection to the
Buchholz relay
Figure 13 – Transformer turret arrangement during filling and filtering operation
The oil treatment plant to be used for the process should have the following characteristics:
Be provided with 1µm filter with ceramic type cartridges. Paper type is not acceptable;
•
able to recirculate under vacuum;
•
sufficient heating power to ensure an oil temperature in the test tank ≥70° C;
•
oil flow ≥ 4000 l/hour;
•
possibility to reverse the oil flow in the turret without disconnecting the pipes.
•
The recommended procedure includes the following steps:
Vacuum in the turret
•
Apply vacuum to the turret via the transformer oil conservator and the Buchholtz relay pipe.
o
Vacuum level ≤ 0.1 kPa (1 mbar).
o
Vacuum time at vacuum level: ≥ 48 h.
o
Oil filling under vacuum from bottom
•
Minimum oil filling characteristics as in Table 12. No air has to remain trapped inside the
o
transformer turret.
At the end of the overall filling process, the air can be evacuated by the air draining plug located
on the main flange of the PHI bushing below the oil expansion vessel (Prysmian type).
Parameter
Water content by Karl Fisher
Breakdown voltage on 2.5 mm gap
Particle content
Inlet oil temperature
HVDC TRANSFORMER BUSHINGS
D
Top valve
Transformer
turret
Oil Flow
Bottom valve
Table 12 – Minimum oil filling parameters for turret filling
PHI 530.1425.2500
PHI 265.850.1500
Kepco project
Vacuum
C
HVDC
transformer
lead
B
ISO11218 Class 0
IS 2664 GB
Page 22 of 70
A
filtering pipe
Turret
manhole
CT
arrangement
PB
barriers
Limit
≤ 3 ppm
> 70 kV
≥70° C
DN 25
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