ABB Relion 670 Series Technical Reference Manual page 284

Section 6
Impedance protection
278
The default settings for AngDir and AngNegRes are 15 (= -15) and 115 degrees
respectively (see figure 142) and they should not be changed unless system studies
show the necessity.
If one sets DirEvalType to Comparator (which is recommended when using the mho
characteristic) then the directional lines are computed by means of a comparator-type
calculation, meaning that the directional lines are based on mho-circles (of infinite
radius). The default setting value Impedance otherwise means that the directional lines
are implemented based on an impedance calculation equivalent to the one used for the
quadrilateral impedance characteristics.
When Directional impedance element for mho characteristic
(ZDMRDIR) is used together with Fullscheme distance protection,
mho characteristic (ZMHPDIS) the following settings for parameter
DirEvalType is vital:
• alternative Comparator is strongly recommended
• alternative Imp/Comp should generally not be used
• alternative Impedance should not be used. This altenative is
intended for use together with Distance protection zone,
quadrilateral characteristic (ZMQPDIS)
X
Zset reach point
AngNegRes
-Zs
en06000416_ansi.vsd
ANSI06000416 V1 EN
Figure 142: Setting angles for discrimination of forward fault
The reverse directional characteristic is equal to the forward characteristic rotated by
180 degrees.
-AngDir R
1MRK505222-UUS C
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