phase identification with load encroachment for mho (FMPSPDIS, 21) function but the influence on
the zone measurement can be switched Enabled/Disabledin the respective impedance measuring
function.
The outline of the characteristic is presented in figure 119. As illustrated, the resistive reach in
forward and reverse direction and the angle of the sector is the same in all four quadrants. The
reach for the phase selector will be reduced by the load encroachment function, as shown in figure
119.
Blinder
Blinder provides a mean to discriminate high load from a fault. The operating characteristic is
illustrated in figure
119. There are six individual measuring loops with the blinder functionality.
Three phase-to-ground loops which estimate the impedance according to
Zn = Vph / Iph
and three phase-to-phase loops according to
Zph-ph = Vph-ph / Iph-ph
The start operations from respective loop are binary coded into one word and provides an output
signal PLECND.
RLd
RLd
LdAngle
LdAngle
LdAngle
LdAngle
R
X
jX
Operation area Operation area
R
Operation area
No operation area No operation area
en06000414_ansi.vsd
ANSI06000414 V1 EN-US
Figure 119: Influence on the characteristic by load encroachment logic
Outputs
SEMOD153832-327 v7
The output of the sequence components based phase selector and the delta logic phase selector
activates the output signals PU_A, PU_B and PU_C. If a ground fault is detected the signal
PHG_FLT gets activated.
The phase selector also gives binary coded signals that are connected to the zone measuring
element for opening the correct measuring loop(s). This is done by the signal PHSCND. If only one
phase is started (A, B or C), the corresponding phase-to-ground element is enabled. PHG_FLT is
expected to be made available for two-phase and three-phase faults for the correct output to be
selected. The fault loop is indicated by one of the decimal numbers below.
Section 7 1MRK 502 066-UUS B
Impedance protection
252
Technical manual
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