11.1 Alarm Levels
The Hydran 201i System is a microprocessor-based family of instruments with
sophisticated alarm features. It is equipped with three alarm levels:
• Gas High alarm (Hydran 201Ti’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 (H201Ti’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 201i System is not functioning properly. A fail alarm must
therefore be verified and solved rapidly because it indicates that the
monitoring system (the Hydran 201i 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.
11.1.1 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 (250ppm, 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 (10ppm 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 (25ppm per 30 days, for example). The daily trend represents the level
variation of gases in the oil during a period of time measured in days. The
daily trend is updated every five minutes.
The complete list of fail alarm conditions is shown in Section 11.5.1. Table 11-1 below
lists the alarm conditions monitored by the Hydran 201Ti.
To Next Page
Loading...
