ABB RELION REX640 Technical Manual page 1386

Condition monitoring functions
Cooling mode
Constant K21 (k
Constant K22 (k
Oil Time Constant
(Շ
0
Winding Tm Constant
(Շ
w
A transformer is a distribution transformer if the
MVA and
setting < 0.833 MVA and
Transformer parameters vary with the material used for winding and insulating
oil. The
can be set individually through the
Constant K21 , Constant K22 , Oil time constant and Winding Tm constant settings.
7.3.5.2 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
Tmp setting.
The formula for calculating the top oil temperature from the measured or set
ambient temperature is shown in
1386
Distribution
Transformers
ONAN
) 1.00
21
) 1.00
22
180
) [minutes]
4
) [minutes]
Transformer type is set to "Three phase" or if the Transformer rating
Transformer type is set to "Single phase".
Parameter Sel method setting can be set to "Manual" and the constants
Parameter Sel method is set to "Manual", the Cooling mode setting has
If
no effect on the transformer parameters.
Since there is no direct
mentioned in the IEEE Std C57.91
(Շ ) and winding time constant (Շ
0
Table 1323
.
For more accuracy, the values of the constants can be entered manually
Parameter Sel method to "Manual".
by setting
Medium and Large power transformers
ONAN ONAF
1.00 1.00
1.00 1.00
210 150
10 7
Transformer rating setting < 2.5
Oil exponent , Winding exponent , Constant K11 ,
Cooling mode based time constants' selection
™
- 2011 standard, the oil time constant
) in Table 1324
w
Equation 322
.
1MRS759142 F
OFAF ODAF
1.00 1.00
1.00 1.00
90 90
7 7
are kept same as in
Average ambient
REX640
Technical Manual