Functions
2.7 Teleprotection for Distance Protection (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
210
Figure 2-100 Reverse interlocking - functional principle and grading example
2.7.12 Transient Blocking
In the overreach schemes, the transient blocking provides additional security against erroneous signals due to
transients caused by clearance of an external fault or by fault direction reversal during clearance of a fault on
a parallel line.
The principle of transient blocking scheme is that following the incidence of an external fault, the formation of
a release signal is prevented for a certain (settable) time. In the case of permissive schemes, this is achieved
by blocking of the transmit and receive circuit.
Figure 2-101 shows the principle of the transient blocking for a permissive scheme.
If, following fault detection, a non-directional fault or a fault in the reverse direction is determined within the
waiting time TrBlk Wait Time (address 2109), the transmit circuit and the release of the overreaching zone
Z1B are prevented. This blocking is maintained for the duration of the transient blocking time TrBlk
BlockTime (address 2110) also after the reset of the blocking criterion. But if a trip command is already
present in Z1, the transient blocking time TrBlk BlockTime is terminated and thus the blocking of the signal
transmission scheme in the event of an internal fault is prevented.
In the case of the blocking scheme, the transient blocking also prolongs the received block signal as shown in
the logic diagram Figure 2-101. After expiration of TrBlk BlockTime (address 2110) the delay time
Release Delay (address 2108) is restarted.
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