Siemens siprotec 7SD5 User Manual page 203

At address 2101 FCT Telep. Dis. the use of a teleprotection scheme can be
turned ON or OFF.
If the teleprotection has to be applied to a three terminal line the setting in address
2102 must be Type of Line = Three terminals, if not, the setting remains Two
Terminals.
The following modes are possible with digital transmission using the protection data
interface:
PUTT (Z1B)
POTT
Dir.Comp.Pickup
The send and receive signals must in these cases be assigned to fast command chan-
nels of the protection data interface (DIGSI matrix).
Distance Protection For all applications of teleprotection schemes (except PUTT), it must be ensured that
Prerequisites the fault detection of the distance protection in the reverse direction has a greater
reach than the overreaching zone of the opposite line end (refer to the shaded areas
in Figure 2-87 on the right hand side)! This is normally predefined for the U/I/ϕ pickup
since the local voltage of a reverse fault is smaller than the voltage of the remote sup-
plying end. For impedance pickup at least one of the distance stages must be set to
Reverse or Non-Directional. During a fault in the shaded area (in the left section
of the picture), this fault would be in zone Z1B of the protection at B as zone Z1B is
set incorrectly. The distance protection at A would not pick up and therefore the pro-
tection in B would interpret this as a fault with single end infeed from B (echo from A
or no block signal at A). This would result in a false trip!
The blocking scheme needs furthermore a fast reverse stage to generate the blocking
signal. Apply zone 3 with non-delayed setting to this end.
Figure 2-87
The send signal prolongation Send Prolong.(address 2103) must ensure that the
Time Settings
send signal reliably reaches the opposite line end, even if there is very fast tripping at
the sending line end and/or the signal transmission time is relatively long. In the case
of the permissive overreaching schemes POTT, Dir.Comp.Pickup and
UNBLOCKING this signal prolongation time is only effective if the device has already
issued a trip command. This ensures the release of the other line ends even if the
short-circuit has been cleared very rapidly by the instantaneous zone Z1. In the case
of the blocking scheme BLOCKING the transmit signal is always prolonged by this
time. In this case it corresponds to a transient blocking following a reverse fault. This
setting is only possible via DIGSI
In order to detect steady-state line faults such as open circuits, a monitoring time
Delay for alarm is started when a fault is detected (address 2107). Upon expira-
7SD5 Manual
C53000-G1176-C169-1
2.7 Teleprotection for Distance Protection (optional)
Permissive Underreach Transfer Trip with Zone Accel-
eration Z1B (PUTT) via protection interface,
Permissive Overreach Transfer Trip (POTT),
Directional comparison pickup,
Distance protection setting with permissive overreach schemes
®
at Additional Settings.
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