7.7.2 Functionality
M12020-4 v14
The increasing utilization of the power system closer to the thermal limits has
generated a need of a thermal overload protection for power lines.
A thermal overload will often not be detected by other protection functions and the
introduction of the thermal overload protection can allow the protected circuit to
operate closer to the thermal limits.
The three-phase current measuring protection has an I
2
t characteristic with settable
time constant and a thermal memory. The temperature is displayed in either Celsius
or Fahrenheit, depending on whether the function used is Thermal overload
protection (LCPTTR) (Celsius) or (LFPTTR) (Fahrenheit).
An alarm level gives early warning to allow operators to take action well before the
line is tripped.
Estimated time to trip before operation, and estimated time to reclose after
operation are presented.
7.7.3 Function block
M12627-3 v8
LCPTTR
I3P*
BLOCK
BLKTR
ENMULT
AMBTEMP
SENSFLT
RESET
TRIP
START
ALARM
LOCKOUT
IEC13000199-1-en.vsd
IEC13000199 V1 EN-US
LFPTTR
I3P*
BLOCK
BLKTR
ENMULT
AMBTEMP
SENSFLT
RESET
TRIP
START
ALARM
LOCKOUT
IEC13000301-1-en.vsd
IEC13000301 V1 EN-US
Figure 110: LCPTTR/LFPTTR function bloc
7.7.4 Signals
PID-3908-INPUTSIGNALS v7
Table 108: LCPTTR Input signals
Name
Type Default Description
I3P GROUP
SIGNAL
- Group signal for current input
BLOCK BOOLEAN 0 Block of function
BLKTR BOOLEAN 0 Block of trip
Table continues on next page
1MRK 506 382-UEN A Section 7
Current protection
Line distance protection REL650 2.2 IEC 231
Technical manual
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