Identification - ABB RELION 670 Series Applications Manual

Section 8
Current protection
8.5.1

Identification

Function description
Thermal overload protection, one
time constant, Fahrenheit
Thermal overload protection, one
time constant, Celsius
8.5.2 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, gets 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 ground faults can occur.
In stressed situations in the power system it can be required to overload lines and cables for a
limited time. This should be done while managing the risks safely.
The thermal overload protection provides information that makes a temporary overloading of
cables and lines possible. The thermal overload protection estimates the conductor temperature
continuously, in Celsius or Fahrenheit depending on whether LFPTTR or LCPTTR (26) is chosen.
This estimation is made by using a thermal model of the line/cable based on the current
measurement.
If the temperature of the protected object reaches a set warning level
can be given to the operator. This enables actions in the power system to be taken before
dangerous temperatures are reached. If the temperature continues to increase to the trip value
TripTemp , the protection initiates trip of the protected line.
8.5.3 Setting guideline
The parameters for the Thermal overload protection, one time constant, Fahrenheit/Celsius
LFPTTR/LCPTTR (26) are set via the local HMI or PCM600.
The following settings can be done for the thermal overload protection.
Operation : Disabled / Enabled
GlobalBaseSel is used to select a GBASVAL function for reference of base values, primary current
IBase ), primary voltage ( UBase ) and primary power ( SBase ).
(
136
IEC 61850 IEC 60617
identification identification
LFPTTR
LCPTTR
1MRK 511 364-UUS A
ANSI/IEEE C37.2
device number
26
26
AlarmTemp , a signal ALARM
Application manual
M17106-1 v7
M15283-3 v8
IP14994-1 v1
M15094-3 v7
M15094-5 v8