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Sequence
The permissive overreach transfer trip only functions for faults in the „Forward" direc-
tion. Accordingly, the first overreach zone ZB1of the distance protection must definite-
ly be set to Forward in addresses 1651 Op. mode Z1B, refer also to Section 2.5.2
under the margin heading „Controlled Zone ZB1".
On two terminal lines, the signal transmission may be phase segregated. Send and
receive circuits in this case are built up for each phase. On three terminal lines, the
transmit signal is sent to both opposite line ends. The receive signals are then com-
bined with a logical AND gate, as all three line ends must transmit a send signal during
an internal fault.
With the parameter Type of Line (address 2102) the device is informed as to
whether it has one or two opposite line ends (Figure 2-73).
During disturbance of the signal transmission path, the overreaching zone Z1B may
be activated by an automatic reclosure (internal or external) via the binary input
„>Enable ARzones".
The occurrence of erroneous signals resulting from transients during clearance of ex-
ternal faults or from direction reversal resulting during the clearance of faults on par-
allel lines, is neutralized by the „Transient Blocking".
On feeders with single-sided infeed, the line end with no infeed cannot generate a
release signal, as no fault detection occurs there. To achieve tripping by the permis-
sive overreach transfer scheme even in this case, the device contains a special func-
tion. This „Weak Infeed Function" (echo function) is referred to in Section „Measures
for Weak and Zero Infeed". It is activated when a signal is received from the opposite
line end — in the case of three terminal lines from at least one of the opposite line ends
— without the device having detected a fault.
The circuit breaker can also be tripped at the line end with no or only weak infeed. This
„Weak-infeed tripping" is referred to in Section 2.10.1.
7SD5 Manual
C53000-G1176-C169-1
2.7 Teleprotection for Distance Protection (optional)
183
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