Directional
detector
BLOCK
RELEASE
Blocking
logic
t
Timer
Low level
blocking
DIRECTION
U3P
I3P
U
1
I
1
Figure 727: Functional module diagram
Directional detector
The Directional detector module compares the angle of the positive-sequence
current I1 to the angle of the positive-sequence voltage V1. Using the positive-
sequence voltage angle as reference, the positive-sequence current angle is
compared to the
Characteristic angle setting. If the angular difference is within the
operating sector selected with the
Directional mode setting, the On signal is sent to
Timer.
The operating sector is defined by the setting
Min forward angle, Max forward
angle, Min reverse angle and Max reverse angle. The options that can be selected for
the
Directional mode setting are “Forward” and “Reverse”.
The sector limits are always given as positive degree values.
The
Characteristic angle setting is also known as Relay Characteristic
Angle (
RCA
), Relay Base Angle or Maximum Torque Line.
Low-level blocking
For a reliable operation, signal levels should be greater than the minimum level.
If they are not greater than the minimum level, Timer is blocked. If the amplitude
of the positive-sequence current is greater than the
Min trip current value and the
positive-sequence voltage amplitude is greater than the
Min trip voltage value, the
On signal is sent to Timer.
Timer
Once activated, the internal operating timer is started. The Timer characteristic is
according to definite time DT. When Timer has reached the value of
Release delay
time, the
RELEASE
output is activated. If a drop-off situation happens, that is, if
the operating current moves outside the operating sector or signal amplitudes drop
1MRS759142 F
Protection related functions
REX640
Technical Manual
1283