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
Figure 135: 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
(Equation 6)
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
1MRS758755 C
Protection functions
REC615 & RER615
Technical Manual
267
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