Functions
2.9 Teleprotection for Earth Fault Protection (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
259
As soon as the earth fault protection has detected a fault in the reverse direction, a blocking signal is transmit-
ted (e.g.
„EF Tele SEND“
, No. 1384). The transmitted signal may be prolonged by setting address
3203
accordingly. The blocking signal is stopped if a fault is detected in the forward direction (e.g.
„EF Tele BL
STOP“
, No. 1389). Very rapid blocking is possible by transmitting also the output signal of the jump detector for
measured values. To do so, the output
„EF Tele BL Jump“
(No. 1390) must also be allocated to the trans-
mitter output relay. As this jump signal appears at every measured value jump, it should only be used if the
transmission channel can be relied upon to respond promptly to the disappearance of the transmitted signal.
The occurrence of erroneous signals resulting from transients during clearance of external faults or from direc-
tion reversal resulting during the clearance of faults on parallel lines is neutralised by „Transient blocking“. The
received blocking signals also prolong the release by the transient blocking time
TrBlk BlockTime
(address
3210
) if it has been present for at least the waiting time
TrBlk Wait Time
(address
3209
), see Figure 2-
126). After expiration of
TrBlk BlockTime
(address
3210
) the delay time
Release Delay
(address
3208
)
is restarted.
It lies in the nature of the blocking scheme that single end fed short-circuits can also be tripped rapidly without
any special measures, as the non-feeding end cannot generate a blocking signal.
2.9.5
Transient Blocking
Transient blocking provides additional security against erroneous signals due to transients caused by clear-
ance 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 2-126 shows the principle of the transient blocking.
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
3209
), the transmit circuit and the trip release are prevented. This
blocking is maintained for the duration of the transient blocking time
TrBlk BlockTime
(address
3210
) also
after the reset of the blocking criterion.
With the blocking scheme the transient blocking prolongs also the received blocking signal as shown in the
logic diagram Figure 2-126. After expiration of
TrBlk BlockTime
(address
3210
) the delay time
Release
Delay
(address
3208
) is restarted.
Figure 2-126
Transient blocking
