GE GL317D, Instruction Manual

Page: 36 / 296

Description and operation
SF
6
gas monitoring
GE Information
07- 2016 L20- 001EN/08
2/6
Gas pressure and density
Introduction
The electrical characteristics of switchgear depend on the density of SF
6
gas
i.e. the mass of gas pumped into a compartment of a given volume.
Constant
temperature
At constant temperature, an increase of gas density results in a higher gas
pressure against the walls of compartment.
Constant density At constant density, with an fixed compartment volume, the pressure
changes in the same way as the temperature. Since the gas density
remains invariable owing to the fact that no modification occurs in the
quantity of gas or the volume of the relevant compartment, the electrical
characteristics of the switchgear will remain unchanged.
Conclusion
Since it is difficult to measure the gas density directly, it is essential to
know accurately its absolute pressure and temperature.