Siemens siprotec 7SA6 User Manual page 264

Functions
Sequence
6-82
A
Z1B(B)
Z1B
T1B
T
(A)
S
&
&
≥1
Z1 or
further
zones
Figure 6-47 Operation scheme of the permissive overreach transfer trip method
Figure 6-48 shows the logic diagram of the signal comparison scheme for one line
end.
The permissive overreach transfer trip only functions for faults in the forward direction.
Accordingly, the overreaching zone Z1B of the distance protection must definitely be
set to )RUZDUG: address  2S PRGH =%, refer also to Sub-section 6.2.4.2
under margin heading "Controlled Zone Z1B".
On lines with two ends 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
send signal is transmitted to both opposite ends. The receive signals are then
combined with the logical AND function, as all three line ends must transmit during an
internal fault. Via the setting /LQH &RQILJ (address ) the device is informed
as to whether it has one or two opposite line ends.
In the case of faults in the transmission path, the overreaching zone Z1B can be
activated by an automatic reclose device, via the binary input "!(QDEOH $5]RQHV"
and address  "1st AR -> Z1B" set to "Yes" (refer to Figure 6-38 bottom).
The influence of signals resulting from transients during clearance of external faults or
from direction reversal during the clearance of faults on parallel lines, is neutralized by
the "Transient Blocking" (refer to Sub-section 6.4.1.10).
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
permissive overreach transfer scheme even in this case, the device contains a special
function. This "Weak Infeed Function" (echo function) is referred to in Sub-section
6.4.1.11. 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 that has only weak or no infeed.
This "Weak-Infeed Tripping" is referred to in Section 6.7.
Z1(B)
≥1
transmit
trip
receive.
Z1(A)
B
Z1B(A)
≥1
transmit
T
S
&
&
≥1
trip
receive.
C53000-G1176-C133-1
Z1B
T1B
(B)
Z1 or
further
zones
7SA6 Manual