ABB Relion 670 series, Technical Reference Manual, Page: 580 / 1232

V=-3V0
Operate region
RCADir
ROADir
Ipickup
I=3Io
mta line
F
en05000253_ansi.vsd
ANSI05000253 V1 EN
Figure 289: CVGAPC, IcosPhi&V directional operating principle
where:
RCADir is -75°
ROADir is 50°
Note that it is possible to decide by a parameter setting how the directional feature
shall behave when the magnitude of the measured voltage phasor falls below the pre-
set value. User can select one of the following three options:
• Non-directional (operation allowed for low magnitude of the reference voltage)
• Block (operation prevented for low magnitude of the reference voltage)
• Memory (memory voltage shall be used to determine direction of the current)
It shall also be noted that the memory duration is limited in the algorithm to 100 ms.
After that time the current direction will be locked to the one determined during
memory time and it will re-set only if the current fails below set pickup level or voltage
goes above set voltage memory limit.
Voltage restraint/control feature
The overcurrent protection step operation can be can be made dependent of a measured
voltage quantity (see table
298 ). Practically then the pickup level of the overcurrent
step is not constant but instead decreases with the decrease in the magnitude of the
measured voltage quantity. Two different types of dependencies are available:
• Voltage restraint overcurrent (when setting parameter VDepMode_OC1 = Slope )
Section 10
1MRK505222-UUS C
Multipurpose protection
574
Technical reference manual