I2Mode: number of phases involved for operation for step2.
I2<: high-set level of the current. If the current decreases below this limit the function
picks up and issue start signals PU_ST2 and RI.
t2: time delay of I2< from the pick-up to the issue of trip signals TRST2 and TRIP.
tReset2: instantaneous or time delayed reset of RI and PU_ST2 signals.
tPulse: duration of all TRIP signals.
IBlk: set level of the currents. If all three phase currents are below this limit the function
blocks the undercurrent protection.
The pick-up level for I1< and I2< should be set with some margin to the lowest current
level, that can appear during normal operation conditions.
7.9 Thermal overload protection, one time constant
Fahrenheit/Celsius LFPTTR/LCPTTR (26)
7.9.1 Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Thermal overload protection, one time
constant, Fahrenheit
LFPTTR 26
Thermal overload protection, one time
constant, Celsius
LCPTTR 26
7.9.2 Application
Lines and cables in the power system are designed for a certain maximum load current
level. If the current exceeds this level the losses will be higher than expected. As a
consequence the temperature of the conductors will increase. If the temperature of the
lines and cables reaches too high values the equipment might be damaged:
1MRK 506 334-UUS A Section 7
Current protection
227
Application manual
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