ABB Relion 670 series - Application; Setting Guidelines; Load Encroachment Characteristics

8.2.2 Application
The operation of transmission networks today is in many cases close to the stability limit.
The ability to accurately and reliably classify the different types of fault, so that single pole
tripping and autoreclosing can be used plays an important role in this matter. Phase
selection with load encroachment function FDPSPDIS (21) is designed to accurately
select the proper fault loop in the distance measuring function depending on the fault type.
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.
8.2.3 Setting guidelines
The following setting guideline consider normal overhead lines applications where φloop
and φline is greater than 60°.
8.2.3.1 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 96)
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
Section 8 1MRK 506 369-UUS -
Impedance protection
216 Line distance protection REL670 2.2 ANSI
Application manual