ABB RES670 Technical Manual page 346

Section 11
Multipurpose protection
340
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 189) and measured voltage phasor
(see table 190). 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 (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 190) and
measured current phasor (see table 189) 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 192 gives an overview of the typical choices (but not the only possible ones) for
these two quantities from traditional directional relays.
Table 192: 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.
Comment
Directional positive sequence overcurrent function is
RCADir is from 45° to 90°
obtained. Typical setting for
depending on the power system voltage level (X/R ratio)
Directional negative sequence overcurrent function is
RCADir is from 45° to 90°
obtained. Typical setting for
depending on the power system voltage level (X/R ratio)
Directional zero sequence overcurrent function is
RCADir is from 0° to 90°
obtained. Typical setting for
depending on the power system grounding (that is, solidly
grounding, grounding 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
RCADir is +30° or +45°
obtained. Typical setting for
Directional overcurrent function for the third phase is
obtained. Typical setting for RCADir is +30° or +45°
Phasor measurement unit RES670 2.2 ANSI
1MRK 511 408-UUS A
M13751-263 v5
Technical manual