ABB Relion 670 Series Technical Reference Manual page 279

1MRK 505 208-UEN B
Technical reference manual
Directional feature
The overcurrent protection step operation can be can be made dependent on the
relevant phase angle between measured current phasor (see table 168) and
measured voltage phasor (see table 169). 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 operate if the current flow is in accordance with the set direction
(Forward, which means towards the protected object, or Reverse, which means
from the protected object). For this feature it is of the outmost importance to
understand that the measured voltage phasor (see table 169) and measured current
phasor (see table 168) 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 just simply use the current and voltage phasors selected by
the end user to check for the directional criteria.
Table 171 gives an overview of the typical choices (but not the only possible ones)
for these two quantities for traditional directional relays.
Table 171: Typical current and voltage choices for directional feature
Set value for the Set value for the
parameter parameter
CurrentInput VoltageInput
PosSeq PosSeq
NegSeq -NegSeq
3ZeroSeq -3ZeroSeq
Phase1 Phase2-Phase3
Phase2 Phase3-Phase1
Phase3 Phase1-Phase2
Unbalance current or voltage measurement shall not be used when the directional
feature is enabled.
Two types of directional measurement principles are available, I & U and
IcosPhi&U. The first principle, referred to as "I & U" in the parameter setting tool,
checks that:
Multipurpose protection
Comment
Directional positive sequence overcurrent function is
obtained. Typical setting for RCADir is from -45° to
-90° depending on the power
Directional negative sequence overcurrent function is
RCADir is from -45° to
obtained. Typical setting for
-90° depending on the power system voltage level (X/
R ratio)
Directional zero sequence overcurrent function is
obtained. Typical setting for RCADir is from 0° to
-90° depending on the power system earthing (that
is, solidly earthed, earthed via resistor)
Directional overcurrent function for the first phase is
RCADir is +30° or +45°
obtained. Typical setting for
Directional overcurrent function for the second phase
is obtained. Typical setting for
Directional overcurrent function for the third phase is
RCADir is +30° or +45°
obtained. Typical setting for
Section 9
RCADir is +30° or +45°
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