Functions
2.7 Teleprotection for Distance Protection (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
206
As soon as the distance protection has detected a fault in the reverse direction, a blocking signal is transmitted
(e.g.
„Dis.T.SEND“
, No. 4056). The transmitted signal may be prolonged by setting address
2103
accord-
ingly. The blocking signal is stopped if a fault is detected in the forward direction (e.g.
„Dis.T.BL STOP“
, No.
4070). Very rapid blocking is possible by transmitting also the output signal of the jump detector for measured
values. To do so, the output
„DisJumpBlocking“
(No. 4060) must also be allocated to the transmitter 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.
If there is a disturbance in the signal transmission path the overreaching zone can be blocked via a binary input.
The distance protection operates with the usual time grading characteristic (non delayed trip in Z1). The over-
reach zone Z1B may, however, be activated by internal automatic reclosure or external criteria via the binary
input
„>Enable ARzones“
.
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
2110
) if it has been present for at least the waiting time
TrBlk Wait Time
(address
2109
), see Figure 2-
101). After expiration of
TrBlk BlockTime
(address
2110
) the delay time
Release Delay
(address
2108
)
is restarted.
The blocking scheme inherently allows even single-end fed short-circuits to be tripped rapidly without any
special measures, as the non feeding end cannot generate a blocking signal.
2.7.10
Pilot Wire Comparison
In the pilot wire comparison the overreaching zone Z1B functions as instantaneous zone at both ends of the
protected line. Zone Z1B is set to reach beyond the next station. The pilot wire comparison avoids non-selective
tripping.
The information exchange between both line ends is carried out via a closed quiescent current loop (Figure 2-
97) fed by a substation battery. One NC contact must be allocated for each signal output, the receiving input
must be configured to „low“-active. As an alternative two auxiliary relay combinations (e.g. 7PA5210-3D) are
possible for inverting the contact.
In the quiescent state the pilot wires carry direct current that, at the same time, monitors the healthy state of
the connection.
If the distance protection picks up, the following signal appears:
„Dis.T.SEND“
. The NC contact is opened
and the pilot wire loop is initially interrupted. A trip by Z1B is blocked via the receiving input
„>DisTel
Rec.Ch1“
. If the protection system then detects a fault within the overreaching zone Z1B, the send signal
resets. The NC contact returns to its quiescent state (closed). If the loop in the remote station is also closed
after the same sequence, the loop is energized again: the tripping is again released at both ends.
In the case where the short-circuit occurred outside the protected line, the pilot wire loop is also interrupted by
the pickup of both devices (both NC contacts
„Dis.T.SEND“
are opened). Since the send signal will not be
reset at least one of the line ends (fault is not in line direction in zone Z1B), the loop at that end will remain
open. Both receiving inputs are deenergized and block the tripping (because of L-active). The other distance
stages including Z1, however, operate independently so that the back-up protection function is not affected.
For lines shorter than the shortest settable line, it must be considered that the first distance zone is either dis-
abled or that T1 is delayed for at least one grading time interval.
If the line has single-end infeed an instantaneous trip for the whole line is possible. Since no pickup occurs on
the non-feeding line end, the loop is not interrupted at that point, but only on the feeding line end. After the fault
is detected within Z1B, the loop will be closed again and the trip command is executed.
