ABB RELION REX640 - 4.4.2.6 Directional overcurrent characteristics

Reliable directional calculation requires that both negative-sequence current and
negative-sequence voltage quantities exceed certain minimum amplitude levels. The
minimum amplitude level for the negative-sequence current is set with the Min
operate current setting. The minimum amplitude level for the polarizing quantity,
that is, the negative-sequence voltage, is set with the Min operate voltage setting.
If the amplitude level of the operating quantity or polarizing quantity is below the
set level, the direction information of the corresponding phase is set to “unknown”.
If the negative-sequence voltage before the fault situation is below Min operate
voltage , the voltage direction cannot be determined.
The value for the Min operate voltage setting should be carefully selected
since the accuracy in low signal levels is strongly affected by the
measuring device accuracy.
Timer
Once activated, Timer activates the START output. The time characteristic is
according to DT. When the operation timer has reached the value set by Operate
delay time , the OPERATE output is activated if the operating signal persists.
In a drop-off situation, that is, if a fault suddenly disappears before the operate
delay is exceeded, the timer reset state is activated. If the reset timer reaches
the value set by Reset delay time , the operate timer resets and the START output
is deactivated. The timer calculates the start duration value START_DUR, which
indicates the percentage ratio of the start situation and the set operation time.
The value is available in the Monitored data view.
Blocking logic
There are three operation modes in the blocking function. The operation modes
are controlled by the BLOCK input and the global setting in Configuration>
System> Blocking mode which selects the blocking mode. The BLOCK input can
be controlled by a binary input, a horizontal communication input or an internal
signal of the protection relay's program. The influence of the BLOCK signal activation
is preselected with the global setting
Blocking mode .
The Blocking mode setting has three blocking methods. In the “Freeze timers”
mode, the operation timer is frozen to the prevailing value, but the OPERATE output
is not deactivated when blocking is activated. In the “Block all” mode, the whole
function is blocked and the timers are reset. In the “Block OPERATE output” mode,
the function operates normally but the OPERATE output is not activated.
4.4.2.6 Directional overcurrent characteristics
The forward and reverse sectors are defined separately. The forward operation area
is limited with the Min forward angle and Max forward angle settings. The reverse
operation area is limited with the Min reverse angle and Max reverse angle settings.
The sector limits are always given as positive degree values.
In the forward operation area, the Max forward angle setting gives the
counterclockwise sector and the Min forward angle setting gives the corresponding
clockwise sector, measured from the Characteristic angle setting.
In the backward operation area, the Max reverse angle setting gives the
counterclockwise sector and the Min reverse angle setting gives the corresponding
Protection functions
1MRS759142 F
828 REX640
Technical Manual