6.2.1 Sources
Alarms can be triggered by one or several of the following sources:
• Gas sources:
Hydran level: This value is measured by the Hydran M2-X gas detector.
Hydran hourly trend: This value is calculated based on the variation of
gas level during a period of time ranging from 1 to 100 hours. The
hourly trend is updated every five seconds.
Hydran daily trend: This value is calculated based on the variation of
gas level during a period of time ranging from 1 to 100 days. The daily
trend is updated every five minutes.
• Moisture sources:
Relative humidity (%RH) level: This value is measured by the Hydran
M2-X moisture sensor.
Relative humidity (%RH) hourly average: This value is calculated based
on the relative humidity calculations made during a period of time
ranging from 1 to 170 hours. The relative humidity average is updated
every five seconds.
Moisture (H
2
O ppm) level: This value is calculated based on the relative
humidity (%RH) and the temperature (see Section K-2).
Moisture (H
2
O ppm) hourly average: This value is calculated based on
the moisture level readings obtained during a period of time ranging
from 1 to 170 hours. The average moisture level is updated every five
seconds.
6.2.2 High and High-High Conditions
The High and High-High alarm conditions are defined as follows:
• High alarm conditions: High conditions are set at a lower value than the
corresponding High-High conditions. They are caution signs; set points for
High alarm conditions should be set at values that indicate that the
transformer (or other equipment) requires closer monitoring.
• High-High alarm conditions: High-High conditions are set at a higher
value. They are warning signs; set points for High-High alarms should be
set at values considered as critical by the user, meaning that the
transformer requires immediate action according to standard utility
procedures. In general, this alarm implies an evaluation of the equipment
and its possible removal from service.
Note: Each analog input could also generate four alarm conditions: Low-Low,
Low, High and High-High.
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