ABB REL670 2.2 IEC Applications Manual page 209

1MRK 506 369-UEN B
Line distance protection REL670 2.2 IEC
Application manual
entire line. It is not necessary to cover all distance protection zones. A safety
margin of at least 10% is recommended. In order to get operation from distance
zones , the phase selection outputs STCNDZ or STCNDLE must be connected to
input on ZMQPDIS, distance measuring block.
For normal overhead lines, the angle for the loop impedance φ for phase-to-earth
fault is defined according to equation 93.
+
X1 XN
j =
arctan L
+
R1 RN
L
EQUATION2115 V1 EN-US
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, RFFwPE and RFRvPE for phase-to-earth faults and
RFFwPP and RFRvPP for phase-to-phase faults have to be increased to avoid that
FDPSPDIS 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.
Phase-to-earth fault in forward direction
With reference to figure 104, 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 and index
Zm reference settings for Distance protection function (ZMQPDIS).
Section 8
Impedance protection
(Equation 93)
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