Siemens siprotec 7SA6, Manual

Page: 289 / 876

Functions
6-99
7SA6 Manual
C53000-G1176-C156-2
6.6.1.5 Directional Comparison Pickup
The following scheme is suited for conventional transmission media.
Principle The directional comparison pickup uses a permissive release principle.
Figure 6-57 shows the operation scheme.
Figure 6-57 Operation scheme of the directional comparison pickup
If the distance protection detects a fault in line direction, it initially sends a release sig-
nal to the opposite line end. If a release signal is also received from the opposite line
end, a trip signal is transmitted to the trip relay. This is only the case if the opposite
line end also detects a fault in line direction. A prerequisite for fast tripping is therefore
that the fault is recognized in both line ends as well as in line direction. The distance
stages operate independent from the directional comparison pickup.
The send signal can be prolonged by T
S
(settable under address
2103A Send Pro-
long.
). The prolongation of the send signal is only active when the protection has al-
ready issued a trip command. This ensures the release from the opposite line end,
even when the fault was cleared locally very fast by the independent zone Z1.
Sequence Figure 6-58 shows the logic diagram of the signal comparison scheme for one line
end.
On lines with two ends, 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
send signal is transmitted to both opposite ends. The receive signals are then com-
bined with the logical AND function, as all three line ends must transmit during an in-
ternal fault. Via the setting
Line Config.
(address
2102
) the device is informed as
to whether it has one or two opposite line ends.
The influence of fault messages resulting from transients during clearance of external
faults or from direction reversal during the clearance of faults on parallel lines, is neu-
tralized by the “Transient Blocking” (refer to Subsubsection 6.6.1.10).
dir.
PU
receive
transmit
A B
Z1(A)
Z1(B)
PICKUP(A)
PICKUP(B)
T
S
&
≥
1
trip
receive
further
zones
&
Z1 or
≥
1
T
S
&
trip
transmit
further
zones
&
Z1 or
≥
1
(A)
dir.
PU
(B)
≥
1
PICKUP(A)
PICKUP(B)