ABB REQ650 - Thermal Overload Protection, One Time Constant Celsius;Fahrenheit LCPTTR;LFPTTR; Identification; Application

IEC Long Time Inverse
IEC Definite time
ASEA RI
RXIDG (logarithmic)
The different characteristics are described in Technical Manual.
tINNonDir is the definite time delay for the non directional earth-fault current
protection, given in s.
OpUN> is set On to activate the trip function of the residual voltage protection.
tUN is the definite time delay for the trip function of the residual voltage protection,
given in s.
6.8 Thermal overload protection, one time constant
Celsius/Fahrenheit LCPTTR/LFPTTR
6.8.1 Identification
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
6.8.2 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:
• The sag of overhead lines can reach unacceptable value.
• If the temperature of conductors, for example aluminium conductors, get too high
the material will be destroyed.
• In cables the insulation can be damaged as a consequence of the overtemperature.
As a consequence of this phase to phase or phase to earth faults can occur
1MRK 505 291-UEN A Section 6
Current protection
131
Application manual