ABB REG670 - Page 207

L1L2 L1L2M
L1L2
0.85 U1 0.15 U1
ArgDir arg ArgNeg Res
I
× + ×
- < <
EQUATION1619 V1 EN (Equation 43)
Where:
ArgDir Setting for the lower boundary of the forward directional characteristic, by default set to 15
(= -15 degrees)
ArgNegRes Setting for the upper boundary of the forward directional characteristic, by default set to
115 degrees, see figure 79 for mho characteristics.
U1
L1
Positive sequence phase voltage in phase L1
U1
L1M
Positive sequence memorized phase voltage in phase L1
I
L1
Phase current in phase L1
U1
L1L2
Voltage difference between phase L1 and L2 (L2 lagging L1)
U1
L1L2M
Memorized voltage difference between phase L1 and L2 (L2 lagging L1)
I
L1L2
Current difference between phase L1 and L2 (L2 lagging L1)
The default settings for ArgDir and ArgNegRes are 15 (= -15) and 115 degrees
respectively (see figure 79) 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)
1MRK502052-UEN B Section 7
Impedance protection
201
Technical manual