Setting Guideline - Hitachi Relion 670 Series Applications Manual

1MRK511407-UUS Rev. N
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 AlarmTemp, a signal 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 TripTemp, the
protection initiates trip of the protected line.
8.5.4

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 (VBase) and primary power (SBase).
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 TRef. It is suggested to set this current to the maximum steady state current 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 ground temperature, ambient air temperature, way of laying of
cable and ground 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 190°F (88°C). For overhead lines, the critical temperature for aluminium
conductor is about 190-210°F (88-99°C). For a copper conductor a normal figure is 160°F (71°C).
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 150°F (66°C). Similar values are stated for overhead lines. A suitable setting can be about
60°F (16°C) 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.
Phasor measurement unit RES670
Application manual
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Section 8
Current protection
IP14994-1 v1
M15094-3 v8
M15094-5 v10
141