ABB RELION 670 Series Technical Manual page 707

1MRK 502 066-UUS B
This feature will simple prevent overcurrent step pickup if the second-to-first harmonic ratio in the
measured current exceeds the set level.
Directional feature
The overcurrent protection step operation can be made dependent on the relevant phase angle
between measured current phasor (see table 409) and measured voltage phasor (see table 410). In
protection terminology it means that the General currrent and voltage protection (CVGAPC)
function can be made directional by enabling this built-in feature. In that case overcurrent
protection step will only trip if the current flow is in accordance with the set direction (
which means towards the protected object, or
For this feature it is of the outmost importance to understand that the measured voltage phasor
(see table 410) and measured current phasor (see table 409) will be used for directional decision.
Therefore it is the sole responsibility of the end user to select the appropriate current and voltage
signals in order to get a proper directional decision. CVGAPC function will NOT do this
automatically. It will simply use the current and voltage phasors selected by the end user to check
for the directional criteria.
Table 412
quantities from traditional directional relays.
Table 412: Typical current and voltage choices for directional feature
Set value for the
parameter
CurrentInput
PosSeq
NegSeq
3ZeroSeq
Phase1
Phase2
Phase3
Unbalance current or voltage measurement shall not be used when the directional feature is
enabled.
Two types of directional measurement principles are available,
principle, referred to as "
• the magnitude of the measured current is bigger than the set pick-up level
• the phasor of the measured current is within the operating region (defined by the relay trip
angle,
Technical manual
gives an overview of the typical choices (but not the only possible ones) for these two
Set value for the
parameter
VoltageInput
PosSeq
-NegSeq
-3ZeroSeq
Phase2-Phase3
Phase3-Phase1
Phase1-Phase2
I & V " in the parameter setting tool, checks that:
ROADir parameter setting; see figure 371).
Reverse , which means from the protected object).
Comment
Directional positive sequence overcurrent function is obtained.
RCADir is from 45° to 90° depending on the power
Typical setting for
system voltage level (X/R ratio)
Directional negative sequence overcurrent function is obtained.
RCADir is from 45° to 90° depending on the power
Typical setting for
system voltage level (X/R ratio)
Directional zero sequence overcurrent function is obtained. Typical
RCADir is from 0° to 90° depending on the power system
setting for
grounding (that is, solidly grounding, grounding via resistor)
Directional overcurrent function for the first phase is obtained.
RCADir is +30° or +45°
Typical setting for
Directional overcurrent function for the second phase is obtained.
RCADir is +30° or +45°
Typical setting for
Directional overcurrent function for the third phase is obtained.
RCADir is +30° or +45°
Typical setting for
Multipurpose protection
Forward ,
I & V and IcosPhi&V . The first
Section 11
M13751-263 v5
701