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Hydran* 201i Instruction Manual
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.
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
), carbon monoxide (CO), acetylene (C
2
• 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.
MA-033
Rev. 14.0, 12-Nov-18
A fail alarm must
H
) and ethylene (C
H
2
2
2
).
4
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