3.6 Heating System
The recommended operating temperature range of the Hydran 201 sensor is 15 to
65°C (59 to 149°F). The sensor temperature is a function of:
• The ambient air temperature surrounding the Hydran 201Ti.
• The oil temperature behind the valve on which the H201Ti is mounted.
Note: This temperature is always lower than the oil temperature at the top of the
transformer tank.
• The thermal regulation of the H201Ti’s temperature.
Regardless of the oil or ambient temperature, the H201Ti is designed (heating and
passive cooling) to maintain the sensor temperature between 25 and 45°C (77 and
113°F), if the set-point is set to the recommended temperature of 35°C (95°F). See Temp
SetPoint parameter in the Temperature and DynOil Sampl submenu at Section 5.5.3.
The H201Ti’s microprocessor measures the temperature and controls the heating
power. A fail alarm is triggered when the sensor temperature is outside the operating
limits. If on, see the FaultTrig parameters in Section 5.5.7.3.
Temperatures are obtained through thermistors incorporated in the sensor body and
the heating plate. The heating plate power is controlled using a time-proportioning
regulating method. The proportional algorithm maintains the sensor temperature near
the desired set point, by modulating it with the dynamic oil sampling system. The
heating plate temperature is limited to 100°C (212°F); its variation rate is also controlled
to avoid sensor overheating.
Detection of an open thermistor shuts the heating power off. In addition, a
thermostat (item 11 in Figure 3-5) with a 100°C (212°F) rating is located on the heating
plate to protect against any fault from the heating system.
3.7 Battery
The Hydran 201Ti’s battery is used to keep the real-time clock functioning when the
unit is not connected to AC power or when AC power is not available. The system
parameter values and historic data are stored in flash memory.
3.7.1 Estimated Life
The battery used is a 3V lithium/manganese dioxide coin cell with a capacity of 950 mAh.
• The battery used has an operating temperature range of -40 to +85˚C (-40 to
+185˚F).
• Normal shelf life of the battery is approximately three (3) years @25˚C.
• Normal service life of the battery is approximately six (6) years @25˚C.
The battery is mounted in a battery holder and the recommended replacement model is
CR2477N from Renata (operating temperature -40 to +85 °C).
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