Description and Functionalities
Monitoring of SF
6
gas
P20--0001EN/02
4/6
01--2011
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GRID
Determination of density
Units of pressure
D The international unit of pressure is the pascal (Pa).
D The practical unit is the bar
1 bar = 1 000 hPa
1 bar = 100 kPa
10 bar = 1 MPa
D Standard atmospheric pressure is equal to 101.3 kPa at sea level and at
a temperature of 20°C.
Measuring the
density
When it is not possible to directly measure the density, it is measured
indirectly using an industrial pressure gauge that measures the
relative
pressure
.
For each assigned density, there is a corresponding assigned relative
pressur evalue, defined for normal atmospheric pressure (101.3 kPa) and
an ambient temperature of 20°C.
For each pressure measurement (filling, verifying the densimeter
thresholds, etc.), the assigned relative pressure must be corrected for the
site’ s atmospheric pressure and the ambient temperature at the time of
measurement. See the ”Calculating the SF
6
gas filling pressure for use
of the pressure gauge (tools)” module.
The real pressure is therefore :
P
real
= P
assigned relative and corrected for temperature
+ ΔPp
*
*
ΔPp: correction for atmospheric pressure.
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