ABB RELION REX640 - Page 531

The minus sign (-) is needed to match the polarity of calculated and
measured residual currents.
The operation of WPWDE can be described with a module diagram. All the modules
in the diagram are explained in the next sections.
Directional
calculation
Level
detector
IRES
Residual
power
calculation
URES
BLOCK
OPERATE
Io
Uo
START
RCA_CTL
t
Timer
t
Blocking
logic
Figure 305: Function module diagram
Directional calculation
The Directional calculation module monitors the angle between the operating
quantity (residual current Io) and polarizing quantity (residual voltage Uo). The
operating quantity can be selected with the setting Io signal Sel . The selectable
options are “Measured Io” and “Calculated Io”. The polarizing quantity can be
selected with the setting Pol signal Sel . The selectable options are “Measured Uo”
and “Calculated Uo”. When the angle between operating quantity and polarizing
quantity after considering the Characteristic angle setting is in the operation
sector, the module sends an enabling signal to Level detector. The directional
operation is selected with the Directional mode setting. Either the “Forward” or
“Reverse” operation mode can be selected. The direction of fault is calculated based
on the phase angle difference between the operating quantity Io and polarizing
quantity Uo, and the value (ANGLE) is available in the monitored data view.
In the phasor diagrams representing the operation of WPWDE, the polarity of the
polarizing quantity (residual voltage Uo) is reversed. Reversing is done by switching
the polarity of the residual current measuring channel (see the connection in the
Protection relay's physical connections section).
If the angle difference lies between -90° to 0° or 0° to +90°, a forward-direction fault
is considered. If the phase angle difference lies within -90° to -180° or +90° to +180°,
a reverse-direction fault is detected. Thus, the normal width of a sector is 180°.
1MRS759142 F
Protection functions
REX640
Technical Manual
531