ABB RELION REX640 Technical Manual page 393

1MRS759142 F
Figure 230: Effect of the Weighting factor p factor and the difference between the
two time constants and one time constant models
The actual temperature of the transformer is calculated by adding the ambient
temperature to the calculated temperature.
Θ = ∆ +
Θ
ΔΘ
Θ
amb
The ambient temperature can be measured with RTD measurement. The measured
temperature value is connected, for example, from the AI_VAL3 output of the X130
RTD function to the AMB_TEMP input of T2PTTR.
The
the ambient temperature measurement value is not connected to the AMB_TEMP
input. The
measurement connected to T2PTTR is set to "Not in use" in the X130 RTD function.
The temperature calculation is initiated from the value defined with the
temperature and Max temperature setting parameters. The initial value is a
percentage of
the protection relay is powered up or the function is turned off and back on or reset
through the Clear menu. The temperature is stored in a nonvolatile memory and
restored if the protection relay is restarted.
The
in degrees Celsius (°C). The value of the
REX640
Technical Manual
Θ Θ
amb
temperature in transformer (°C)
calculated temperature rise (°C) in transformer
set value of the
ture
Env temperature Set setting is used to define the ambient temperature if
Env temperature Set setting is also used when the ambient temperature
Max temperature defined by Initial temperature . This is done when
Max temperature setting defines the maximum temperature of the transformer
Env temperature Set setting or measured ambient tempera-
Max temperature setting is usually given by
Protection functions
(Equation 37)
Initial
393