User`s guide

Chapter 8 ____________________________Measuring Moisture in SFB6B Gas-insulated Equipment
CHAPTER 8
MEASURING MOISTURE IN SF
6
GAS-
INSULATED EQUIPMENT
Overview
Sulfur Hexafluoride (SF
6
) is an inert, insulating gas of high dielectric
strength and thermal stability. SF
6
is used to insulate high voltage
lines, circuit breakers, and other equipment used in transmission and
distribution of electricity. Measuring moisture is crucial for the
maintenance of SF
6
equipment.
The DMP74C probe has been optimized for measurements in SF
6
gas.
The measurement is recommended to be made in pressurized gas for
better dewpoint accuracy. The sensor purge feature of the DRYCAP
®
180M allows a fast response in low dewpoints, and only a small
amount of SF
6
needs to be drained from the GIE.
SF6 is a greenhouse gas, with a global warming potential 24900 times
that of CO
2
. For this reason, the gas should be recycled according to
the local laws and regulations. The DSC74B sampling cell allows the
gas to be collected after the measurement, see Figure 29 on page 62.
When m
easurement is done in the GIE pressure, the structure of
DSC74B eliminates the adverse effect of pressure fluctuation caused
by the collection system.
VAISALA _______________________________________________________________________ 61