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(vi) Delay of trip permission signal
Figure 2.12-4 shows POP sending circuit. The trip permission signals are (DISCAR-S: used for
the external carrier communication) and (INT.DISCAR-S-*: used for the integral carrier
communication). The selection of either the single-phase trip (1P) or the three-phase trip (3P)
is carried out using scheme switch [DisCAR-TPMD].
Transmission of the trip permission signal continues for setting [TSBCT-dis] even after
the local terminal issues a trip signal.
In many cases, at both ends of the line, the overreaching elements operate at the same
time. However, there may be some cases where they cannot operate simultaneously because
fault currents do not flow symmetrically. That is, the overreaching elements far from a fault
cannot operate by the fault, but the overreaching elements far from the fault will be operated
indirectly if the other terminals are induced to trip. To avoid this case, transmission of the trip
permission signal continues for a while set by [TSBCT-dis] after reset of ZCSF/ZCSG operation.
Consequently, the overreaching elements far from the fault can also generate a trip signal
because the trip permission signal is picked up delayed.
Thus, this command protection ensures its operation at the remote terminal.
800000EB55 DISCAR_F.BLOCK
used for the
integral carrier
communication
used for the
external carrier
communication
Figure 2.12-4 Sending circuit in POP and UOP
2.12.3 Unblocking overreach protection (UOP)
When information are exchanged using a transmission line (the power line carrier), PUP and
POP cannot trip dependably. This is because a trip permission signal may not be exchanged
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