6.6.1 Identification
M17106-1 v7
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Thermal overload protection, one time
constant, Celsius
LCPTTR 26
Thermal overload protection, one time
constant, Fahrenheit
LFPTTR 26
6.6.2 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.
Section 6 1MRK 505 384-UEN A
Current protection
140 Breaker protection REQ650 2.2 IEC
Technical manual
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