ABB RED615 Technical Manual page 233

1YHT530004D05 D
615 series
Technical Manual
I_A
Max
I_B current
selector
I_C
ENA_MULT
BLK_OPR
AMB_TEMP
A070747 V3 EN
Figure 116: Functional module diagram. I_A, I_B and I_C represent phase
currents.
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
Θ =   ⋅ T
final ref
 
I
ref
 
A070780 V2 EN
I the largest phase current
I set Current reference
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 emergency operation for a few hours per years. Current values with the
corresponding conductor temperatures are given in cable manuals. These values are
given for conditions such as ground temperatures, ambient air temperature, the way
of cable laying and ground thermal resistivity.
Thermal counter
The actual temperature at the actual execution cycle is calculated as:
Temperature
estimator
Thermal
counter
Section 4
Protection functions
START
OPERATE
ALARM
BLK_CLOSE
(Equation 3)
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