ABB REL650 Applications Manual page 160

Section 6
Impedance protection
154
en06000551_ansi.vsd
ANSI06000551 V1 EN
Figure 72: 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 Five zone distance protection, quadrilateral characteristic
function (ZQMPDIS, 21) and Phase selection with load encroachment, quadrilateral
characteristic function FDPSPDIS (21) as shown in figure 73. 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.
1MRK 506 334-UUS A
Application manual