Functionality - ABB REL650 series Technical Manual

1MRK 506 335-UUS A
7.9.2
7.9.3
Technical manual

Functionality

The increasing utilizing of the power system closer to the thermal limits has generated a
need of a thermal overload protection also 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
constant and a thermal memory. The temperature is displayed in either in Celsius or in
Fahrenheit depending on whether the function used is Thermal overload protection one
time constant, Fahrenheit LFPTTR (26) or Celsius LCPTTR.
An alarm pickup 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.
Function block
LFPTTR (26)
I3P* TRIP
BLOCK
AMBTEMP ALARM
SENSFLT LOCKOUT
RESET TEMP
TEMPAMB
TERMLOAD
ANSI11000246-1-en.vsd
ANSI11000246 V1 EN
LCPTTR (26)
I3P* TRIP
BLOCK
AMBTEMP ALARM
SENSFLT LOCKOUT
RESET TEMP
TEMPAMB
TERMLOAD
ANSI08000038-2-en.vsd
ANSI08000038 V2 EN
Figure 113: LFPTTR/LCPTTR (26) function block
RI
RI
Section 7
Current protection
2
t characteristic with settable time
249