HVDC TRANSFORMER BUSHINGS
PHI 530.1425.2500
PHI 265.850.1500
Kepco project
IS 2664 GB
Page
24
of
70
8
Gas SF6 characteristics and gas filling instructions
The SF6 gas to be used to fill the bushing must comply with the data shown in the following
Table 14
. This table
shows the limits stated by GE Energy Connections RPV specification and the characteristics of a Premium
Supplier:
Characteristics
Unit
GE Energy
Connections RPV
limits
Premium
Supplier’s limits
Min SF6
% by weight
≥
99.9%
≥
99.993%
Air
ppm by weight
≤
500 ppm w
≤
50 ppm w
CF4
ppm by weight
≤
500 ppm w
≤
10 ppm w
H
2
O
ppm by weight
≤
15 ppm w
≤
0.65 ppm w
Dew point @ atmospheric pressure
°C
≤
-40°C
≤
-65°C
Mineral oil
ppm by weight
≤
10 ppm w
≤
1 ppm w
Total acidity expressed in HF
ppm by weight
≤
0.3 ppm w
≤
0.3 ppm w
Hydrolizable fluorides in terms of HF
ppm by weight
≤
1 ppm w
≤
1 ppm w
Table 14 - Characteristics of new SF6 gas according GE Energy Connections RPV and premium
Supplier
The minimum requirement is that the characteristics have to be in accordance with the data listed in the GE
Energy Connections RPV limits column.
Before proceeding with filling or re-filling operations the gas characteristics must be checked and the data must
be reported in the Gas filling check list, see
Appendix 8
.
The gas filling must be performed with an equipment that prevents dispersion of the SF6 gas in the atmosphere.
As an example, next
Figure 14
shows a gas plant manufactured by the German company DILO GmbH.
Figure 14 – Vacuum filling gas plant DILO
NOTE:
This bushing has to be operated with pure SF6. In case of need of replacement of SF6 gas with a mixture
SF6 N2, before proceeding, please contact GE Energy Connections RPV for instructions and approval.
WARNING: The following safety notes are mandatory.
•
The bushing can be filled at the rated filling pressure of 0.63 MPa abs (5.3 bar gauge @ 20°C), only
when installed on the transformer ready for the electrical tests or placed inside valve hall wall.
•
If, for any reason, the bushing has to be removed from the transformer turret, it is mandatory to
reduce the gas pressure to 0.125 MPa abs (0.25 bar gauge) before proceeding with the operation.
•
If the transformer is stored with the bushings installed, the gas pressure must be reduced to 0.150 MPa
abs (0.5 bar gauge) and periodically checked.
•
All gas filling and gas recovering operations must be performed by a gas plant device (example a DILO
machine).
WARNING: Before proceeding with the gas filling operation, remove the Transport pressure gauge (see
Paragraph 3.1 and Figure 1).