GE Hydran 201i, Инструкция по эксплуатации

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Alarm Levels
Part 17997 Rev. 6, March 2011 10-3
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 10.5.1 on page 10-14.
Table 10-1 on page 10-3 lists the alarm conditions monitored by the Hydran 201T i .
Table 10-1 - Alarm Conditions Monitored by the Hydran 201T
i
10.1.2 Purpose of Hourly and Daily Trends
Detection of hourly and daily trend alarm conditions is a unique feature of the
Hydran 201
i System that provides early warning of slowly increasing gas level. For
example, let us consider a transformer with a 50-ppm gas level and a typical gas High alarm
set point of 150 ppm.
• If no trend alarm is used and if the gas level reading starts increasing at the rate of 50 ppm
per month, it takes two months before the gas High alarm condition is detected and the
investigation of the possible causes of the increase begins (unless the gas reading was
already closely monitored).
• If the daily trend High alarm is used and its alarm set point is adjusted to 25 ppm, its
period to 30 days and its alarm delay to 33 % of the period (10 days), the alarm would
occur approximately 23 days after the beginning of the gas level increase. Investigation
of the possible causes could thus start five weeks earlier. For details on trend computa-
tions, see Section 10.4.3 on page 10-12.
Source Possible States
Gas level
Low-Low Low
High High-High
Hourly trend
Daily trend
Sensor temperature
Battery voltage — —
Sensor and connections Cable
a
short
a. Either one of the following cables (or connectors in the connection link): Sensor, sensor
thermistor, or heating plate thermistor.
Replace
sensor soon Replace
sensor now
Cable
a
open