2.7 Teleprotection for Distance Protection (optional)
199
7SD5 Manual
C53000-G1176-C169-1
Figure 2-84
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 2-85 shows the principle of the transient blocking for a directional comparison
and 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
(ad-
dress
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 prolongs the received block
signal as shown in the logic diagram Figure 2-85.
www
. ElectricalPartManuals
. com
