GE GL317D - Page 130

Installation
Calculation of th e SF
6
gas f illing pressure
for using the p ressure gauge (tool)
GE Information L31- 921EN/03
2/4
02- 2017
Technical d ata
SF
6
gas
The table below gives the SF
6
gas characteristics :
Absolute pressure at 20C(68F)
p
re
Filling absolute pressure for the insula-
tion
0.65 MPa
(94.27 p.s.i.)
i.e. effective pressure
at 20C(68F) and 101.3 kPa
p
re
Filling rated effective pressure
for the insulation
+0,01
-0
0.55 MPa
(79.77 p.s.i.)
p
ae
Alarm effective pressure for the
insulation
+0,02
-0
0.45 MPa (p
me
+0.03 MPa)
(65.27 p.s.i.)
p
me
Minimal effective pressure for
the insulation
+0,02
-0
0.42 MPa
(60.92 p.s.i.)
SF6 gas density
p
re
42,38 kg/m
3
p
ae
35,38 kg/m
3
p
me
33,31 kg/m
3
Minimum admissible temperature
up to
-35C
Example
Determination of the circuit- breaker’ s filling pressure with SF
6 gas.
Parameters
Values
p
re
SF
6
gas rated filling effective
pressure for the insulation
0,55 MPa
(79.77 psi)
Ambient temperature 5C
Local atmospheric pressure 93,2 kPa
SF
6
gas filling
The table below gives the calculation steps of the pure SF
6
filling pressure :
Step
Action Result
1 In the chart (page 4) “Values of the
SF
6
gas effective pressures in
accordance with the temperature”,
read the p
re
valueonthe
tC=5row.
0,51 MPa
2 Calculate the difference of the
atmospheric pressure :
0,1013 - 0,0932
0,0081 MPa
3 Calculate the rated effective pres-
sure p
re
:
0,510 + 0,0081
0,5181 MPa
4 Filling is carried out to the calcu-
lated pressure, plus 0,01 MPa,
that is to say :
0,5181 + 0,01
Pure SF
6
gas filling pressure
0,5281 MPa