Setting Guideline - ABB RELION 670 Series Applications Manual

Section 8
Current protection
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 LCPTTR or LFPTTR
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
ALARM 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
8.7.3

Setting guideline

The parameters for the Thermal overload protection, one time constant, Celsius/Fahrenheit
LCPTTR/LFPTTR are set via the local HMI or PCM600.
The following settings can be done for the thermal overload protection.
Operation : Off / On
GlobalBaseSel is used to select a GBASVAL function for reference of base values, primary
current (
Imult : Enter the number of lines in case the protection function is applied on multiple parallel
lines sharing one CT.
IRef : Reference, steady state current, given in % of IBase that will give a steady state (end)
temperature rise
allowed for the line/cable under emergency operation (a few hours per year).
TRef : Reference temperature rise (end temperature) corresponding to the steady state current
IRef . From cable manuals current values with corresponding conductor temperature are often
given. These values are given for conditions such as earth temperature, ambient air
temperature, way of laying of cable and earth thermal resistivity. From manuals for overhead
conductor temperatures and corresponding current is given.
Tau : The thermal time constant of the protected circuit given in minutes. Please refer to
manufacturers manuals for details.
TripTemp : Temperature value for trip of the protected circuit. For cables, a maximum allowed
conductor temperature is often stated to be 90°C (194°F). For overhead lines, the critical
temperature for aluminium conductor is about 90 - 100°C (194-212°F). For a copper conductor
a normal figure is 70°C (158°F).
AlarmTemp : Temperature level for alarm of the protected circuit. ALARM signal can be used as
a warning before the circuit is tripped. Therefore the setting shall be lower than the trip level.
It shall at the same time be higher than the maximum conductor temperature at normal
operation. For cables this level is often given to 65°C (149°F). Similar values are stated for
overhead lines. A suitable setting can be about 15°C (59°F) below the trip value.
ReclTemp : Temperature where lockout signal LOCKOUT from the protection is released. When
the thermal overload protection trips a lock-out signal is activated. This signal is intended to
block switch in of the protected circuit as long as the conductor temperature is high. The
signal is released when the estimated temperature is below the set value. This temperature
value should be chosen below the alarm temperature.
430
TripTemp , the protection initiates trip of the protected line.
IBase ), primary voltage ( UBase ) and primary power ( SBase ).
TRef . It is suggested to set this current to the maximum steady state current
1MRK 504 152-UEN B
AlarmTemp , a signal
IP14994-1 v1
M15094-3 v7
M15094-5 v8
Application manual