ABB RELION 620 Series Technical Manual page 462

Section 4
Protection functions
4.2.7.4
456
The function contains a blocking functionality. It is possible to block function outputs,
timers or the function itself, if desired.
Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
For WPWDE, certain notations and definitions are used.
Residual voltage Uo = (UA+UB+UC)/3 = U
sequence voltage
Residual current Io = -(IA+IB+IC) = 3×- I
current
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.
Io
Directional
calculation
Uo
RCA_CTL
Residual
power
calculation
Blocking
BLOCK
logic
GUID-2E3B73F0-DB0D-4E84-839F-8E12D6528EEC V1 EN
Figure 229: 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.
Timer
Level
detector t
t
1MRS757644 F
, where U = zero-
0 0
, where I = zero-sequence
0 0
OPERATE
START
620 series
Technical Manual