ABB Relion 670 series - Setting Guidelines; Load Encroachment Characteristics

The heavy load transfer that is common in many transmission networks may in some cases
be in opposite to the wanted fault resistance coverage. Therefore, the function has a built
in algorithm for load encroachment, which gives the possibility to enlarge the resistive
setting of both the Phase selection with load encroachment and the measuring zones
without interfering with the load.
A current-based phase selection is also included. The measuring elements continuously
measure three phase currents and the residual current and, compare them with the set
values.
The extensive output signals from FDPSPDIS (21) give also important information about
faulty phase(s), which can be used for fault analysis.
8.11.3 Setting guidelines
The following setting guideline consider normal overhead lines applications where φloop
and φline is greater than 60°.
8.11.3.1 Load encroachment characteristics
The phase selector must at least cover the overreaching zone 2 in order to achieve correct
phase selection for utilizing single-phase autoreclosing for faults on the 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
PHSELZ or DLECND must be connected to input PHSEL 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
96.
L
L
X1
arctan
R1
+
j =
+
XN
RN
EQUATION2115 V1 EN (Equation 281)
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.
Section 8 1MRK 506 369-UUS -
Impedance protection
348 Line distance protection REL670 2.2 ANSI
Application manual