temperature rise continues the function operates based on the thermal model of the
line.
Re-energizing of the line after the thermal overload operation can be inhibited during
the time the cooling of the line is in progress. The cooling of the line is estimated by
the thermal model.
4.1.3.4 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of T1PTTR can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
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.
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 136: 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 6)
1MRS758755 A Section 4
Protection functions
REC615 and RER615 253
Technical Manual
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