ABB Relion 611 Series, Technical Manual

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Temperature
estimator
Thermal
counter
ENA_MULT
ALARM
BLK_CLOSE
OPERATE
BLK_OPR
START Max
current
selector
I_A
I_B
I_C
AMB_TEMP
A070747 V3 EN
Figure 60: 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:
Θ
final
ref
ref
I
I
T
=








⋅
2
A070780 V2 EN
(Equation 2)
I the largest phase current
I
ref
set
Current reference
T
ref
set
Temperature rise
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:
Section 4
1MRS757454 D
Protection functions
132 611 series
Technical Manual