3
V
0
V
A
V
B
V
C
V
B
F
V
C
F
V
C
F
en06000551_ansi.vsd
ANSI06000551 V1 EN
Figure 244: The voltage increase on healthy phases and occurring neutral point
voltage (3V0) at a single phase-to-ground fault and an occurring cross-
country fault on different feeders in a sub-transmission network, high
impedance (resistance, reactance) grounded
PPLPHIZ is connected between Distance protection zone, quadrilateral characteristic
function ZMQPDIS (21) and ZMQAPDIS (21) and Phase selection with load
encroachment, quadrilateral characteristic function FDPSPDIS (21) as shown in
figure
245. The integer from the phase selection function, which gives the type of fault
undergoes a check and will release the distance protection zones as decided by the logic.
The logic includes a check of the fault loops given by the phase selection and if the fault
type indicates a two or three phase fault the integer releasing the zone is not changed.
If the fault indicates and ground-fault checks are done which mode of tripping to be used,
for example ABCAc, which means that fault in the phases are tripped in the cyclic order A
before B before C before A. Local conditions to check the phase-to-ground voltage levels
and occurring zero sequence current and voltages completes the logic.
Section 8 1MRK 506 369-UUS -
Impedance protection
478 Line distance protection REL670 2.2 ANSI
Application manual
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