ABB REL650 Applications Manual page 146

Section 6
Impedance protection
140
STCNDZI or DLECND must be connected to input STCNDZI on ZMQPDIS (21),
distance measuring block.
For normal overhead lines, the angle for the loop impedance φ for phase-to-ground fault
is defined according to equation 59.
+
X1 XN
j =
arctan L
+
R1 RN
L
EQUATION2115 V1 EN
In some applications, for instance cable lines, the angle of the loop might be less than 60°.
In these applications, the settings of fault resistance coverage in forward and reverse
direction, RFltFwdPG and RFltRevPG for phase-to-ground faults and RFltRevPP and
RFltRevPP for phase-to-phase faults have to be increased to avoid that FDPSPDIS (21)
characteristic shall cut off some part of the zone characteristic. The necessary increased
setting of the fault resistance coverage can be derived from trigonometric evaluation of the
basic characteristic for respectively fault type.
GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(VBase) and (SBase).
Phase-to-ground fault in forward direction
With reference to figure 67, the following equations for the setting calculations can be
obtained.
Index PHS in images and equations reference settings for Phase selection
with load encroachment function FDPSPDIS (21) and index Zm reference
settings for Distance protection function (ZQMPDIS, 21).
1MRK 506 334-UUS A
(Equation 59)
Application manual