ABB RELION REX640 Technical Manual page 367

1MRS759142 C
REX640
Technical Manual
The function uses ambient temperature which can be measured locally or remotely.
Local measurement is done by the protection relay. Remote measurement uses analog
GOOSE to connect AMB_TEMP input.
If the quality of remotely measured temperature is invalid or
communication channel fails the function uses ambient temperature
set in Env temperature Set.
I_A
I_B
I3P
I_C
ENA_MULT
AMB_TEMP
BLK_OPR
GUID-C4701C34-BF1F-46A9-B005-1C82CA9BB886 V1 EN
Figure 202: Functional module diagram
Max current selector
The max current selector of the function continuously checks the highest measured
TRMS phase current value. The selector reports the highest value to the temperature
estimator.
Temperature estimator
The final temperature rise is calculated from the highest of the three-phase currents
according to the expression:
2
I
 
T
Θ =  ⋅
final  ref
I
ref
 
GUID-B89A7FFC-740E-40A7-A5D0-E70C7C674A44 V1 EN
I the largest phase current
Current reference
I set
ref
Temperature rise
T set
ref
The ambient temperature is added to the calculated final temperature rise estimation,
and the ambient temperature value used in the calculation is also available in the
monitored data as TEMP_AMB in degrees. If the final temperature estimation is larger
than the set Maximum temperature, the START output is activated.
Current reference and Temperature rise setting values are used in the final
temperature estimation together with the ambient temperature. It is suggested to set
these values to the maximum steady state current allowed for the line or cable under
Max current
Temperature
selector estimator
Section 4
Protection functions
START
OPERATE
Thermal
ALARM
counter
BLK_CLOSE
(Equation 30)
361