Siemens siprotec 7SD5 User Manual page 193

Sequence Figure 2-80 shows the logic diagram of the blocking scheme for one line end.
The overreach zone Z1B is blocked which is why it must be set to Forward (address
1651 Op. mode Z1B, see also Section 2.5.1 at margin heading „Controlled Zone
Z1B").
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 signals are sent to both opposite line ends. The receive signals are then com-
bined with a logical OR gate as no blocking signal must be received from any line end
during an internal fault. With the setting parameter Type of Line (address 2102)
the device is informed as to whether it has one or two opposite line ends.
7SD5 Manual
C53000-G1176-C169-1
2.7 Teleprotection for Distance Protection (optional)
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