GE Hydran 201i, Instruction Manual

Page: 192 / 300

Chapter 10 • Alarms
10-2 Rev. 6, March 2011 Part 17997
10.1 ALARM LEVELS
The Hydran 201 i System is a microprocessor-based family of instruments with sophisti-
cated alarm features. It is equipped with three alarm levels:
• Gas High alarm (Hydran 201T i ’s Alarm 1): This alarm is set at a lower gas level than
the High-High alarm. It is a caution sign and should initiate closer monitoring of the
equipment.
• Gas High-High alarm (H201T i ’s Alarm 2): This alarm is set at a higher level than the
High alarm. It is a warning sign and should trigger immediate operator action according
to standard utility procedures.
• Fail alarm of the Hydran 201i System : This alarm includes all alarms other than the High
and High-High alarms. The fail alarm warns the operator that the Hydran 201 i System is
not functioning properly. A fail alarm must therefore be verified and solved rapidly
because it indicates that the
monitoring system (the Hydran 201 i System) of the
transformer is faulty.
Note: A fail alarm does not concern the transformer.
The High and High-High alarms provide an early warning of incipient faults in trans-
formers or any other oil-filled electrical equipment.
10.1.1 Alarm Conditions
An alarm is triggered when an alarm condition is detected. Each alarm has its own set of
alarm conditions.
Gas High and High-High alarms are triggered by one or several of the following conditions:
• The level of gases in oil exceeds the user-defined alarm set point (250 ppm, for example).
The gas level is a composite value of the following gases: Hydrogen (H
2
), carbon
monoxide (CO), acetylene (C
2
H
2
) and ethylene (C
2
H
4
).
• The hourly trend (short term) of the gas level exceeds the user-defined alarm set point
(10 ppm per 24 hours, for example). The hourly trend represents the level variation of
gases in the oil during a period of time measured in hours. The hourly trend is updated
every five seconds.
• The daily trend (long term) of the gas level exceeds the user-defined alarm set point
(25 ppm per 30 days, for example). The daily trend represents the level variation of gases