8.2.2 Application
M13138-3 v3
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
IP14959-1 v2
The following setting guideline consider normal overhead lines applications where
φloop and φline is greater than 60°.
8.2.3.1 Load encroachment characteristics
M13142-3 v6
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
101.
EQUATION2115 V1 EN-US (Equation 101)
1MRK 504 163-UUS A Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI 249
Application manual
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