Siemens GAS-Guard 3, Operation And Maintenance Manual, Page: 8 / 20

GAS-Guard 8 and GAS-Guard 3 Operations and Maintenance Guide 810-1734-00 Rev A
6 of 18
New transformers or transformers with no previous gas data:
Set the GAS-Guard caution level to 50% and the alarm level to 100% of the low-end CAUTION ppm
limits proposed by IEEE PC57.104 Draft 11, published April 21, 2004; except acetylene, as noted below.
Gas Caution PPM Alarm PPM Notes:
Hydrogen 50 100
Methane 60 120
Acetylene 2 5 Per Draft 11
Ethylene 25 50
Ethane 33 65
Carbon Monoxide 175 350
Carbon Dioxide 1750 3500
Oxygen b10% B20% above initial measured PPM
Table 2: Recommended caution/alarm settings for transformers with no previous gas data
Transformers with a stable gassing history:
Use the GAS-Guard to measure the transformer oil for thirty (30) days in order to establish baseline
levels of the eight fault gases. Set the GAS-Guard caution/alarms levels to the measured baseline levels
+ value (PPM) shown below.
Gas
Caution PPM
+value (PPM)
Alarm PPM
+value (PPM)
Notes:
Hy50 +100
M60 +120
Ace2 +5
Et25 +50
33 +65
Carbon Monoxide +175 +350
Carbon Dioxide +1750 +3500
Oxygen b10% B20% above initial measured PPM
Table 3: Recommended caution/alarm settings for transformers with a stable gassing history