ABB RELION REX640 Technical Manual page 1281

1MRS759142 C
REX640
Technical Manual
A transformer is a distribution transformer if the Transformer rating setting < 2.5
MVA and Transformer type is set to "Three phase" or if the Transformer rating setting
< 0.833 MVA and Transformer type is set to "Single phase".
Transformer parameters vary with the material used for winding and insulating oil.
The Parameter Sel method setting can be set to "Manual" and the constants can be set
individually through the Oil exponent, Winding exponent, Constant K11, Constant
K21, Constant K22, Oil time constant and Winding Tm constant settings.
If Parameter Sel method is set to "Manual", the Cooling mode setting
has no effect on the transformer parameters.
Since there is no direct Cooling mode based time constants' selection
mentioned in the IEEE Std C57.91™- 2011 standard, the oil time
constant (Շ
kept same as in the
For more accuracy, the values of the constants can be entered
manually by setting Parameter Sel method to "Manual".
Top oil temp calculation
The function receives two sensor inputs for measuring top oil temperature and
ambient temperature.
The top oil temperature of the tank is obtained through a sensor placed at the upper
inner turn of the winding. If the top oil temperature sensor status TOIL_SNSFLT is
FALSE, the top oil temperature is directly obtained from the TOIL_TEMP input.
If the status of TOIL_SNSFLT is TRUE, indicating that the sensor is faulty, the top
oil temperature is calculated with the help of measured ambient temperature.
The status of the ambient temperature sensor is obtained through the AMB_SNSFLT
binary input. If AMB_SNSFLT is FALSE, indicating the healthy status of the sensor,
the ambient temperature is directly measured through the AMB_TEMP input. Else, if
AMB_SNSFLT is TRUE, the ambient temperature is taken from the Average ambient
Tmp setting.
The formula for calculating the top oil temperature from the measured or set ambient
temperature is shown in
 
1

Dt (
+

D
θ

= ⋅
n
0
( ) k 1

τ
( )
⋅

11 o



GUID-B018BF38-A4E1-4B1F-984E-87AE16B66C4C V1 EN
Where
Condition monitoring functions
) and winding time constant (Շ
0
Table 1200.
Equation 287.
x
2
K R

)
⋅

θ θ

⋅ ∆ − −
or
n
0 1
R ( )
−

+


Section 7
) in the Table 1201
w



θ
a




are
(Equation 287)
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