Table of Contents
Advertisement
HMI: Settings/Gas monitoring
Figure 66 – Gas pressure thresholds
A comparison is constantly made between the current gas pressure value normalised at
o
20
C and the various thresholds (1, 2, 3) values set. If any is reached, then a threshold alarm
is raised.
HMI: Measurements/Alarms
Figure 67 – Gas pressure alarms
Gas liquefaction risk
As seen in the graphs at the beginning of this section (Figure 60 – Equivalent density lines
and liquefaction curve), the liquefaction curve indicates at which temperature and pressure
the SF6 gas will change from gas phase to liquid phase. At normal ambient temperature, the
liquefaction pressure is very high and is not a problem, but when the temperature falls
below freezing, the liquefaction pressure gets closer to our operating pressure range.
o
o
Therefore, if the gas temperature falls below 3
C (37.4
F), the liquefaction pressure for the
o
gas (or gas mixture) at 20
C is displayed so that it can be compared to the current gas
o
pressure at 20
C. Until the gas temperature reaches that point, a "-" value is displayed as it
is not relevant to display it.
HMI: Measurements/Gas
Figure 68 – Gas liquefaction pressure
o
If the current gas pressure value normalised at 20
C falls below the known liquefaction
o
pressure for the gas at 20
C, then a liquefaction risk alarm is raised.
MA-037 - CB Watch 3 Operating Manual
v7.0 - May 2020
Page 49 of 118
Advertisement
Table of Contents
