2.6 Teleprotection for distance protection
147
7SA522 Manual
C53000-G1176-C155-3
Digital Transmis-
sion
The following modes are possible with digital transmission using the protection data
interface (described in Subsection 2.6):
3877=% Permissive Underreach Transfer Trip with Zone Accel-
eration Z1B (PUTT) via protection interface,
3277 Permissive Overreach Transfer Trip (POTT).
The desired mode is selected in address )&77HOHS'LV. The use of a tele-
protection scheme can also be turned 21 or 2)) here. Address 180%(52)
5(/$< indicates the number of ends and must be set identically in all devices. The
distance protection scheme via the protection data interface is only active if parameter
7HOHSURW'LVW was set to 6,*1$/Y3URW,QW for all devices in a constel-
lation.
Distance Protection
Prerequisites
For all applications of teleprotection schemes (except PUTT), it must be ensured that
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 2-62 on the right hand side)! To this end, at least one of the distance stages
must be set to 5HYHUVH or 1RQ'LUHFWLRQDO. 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 there-
fore the protection 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 2-62 Distance protection setting with permissive overreach schemes
Time Settings The send signal prolongation 6HQG3URORQJ(address ) must ensure that the
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 3277 and 81%/2&.,1* this signal prolon-
gation 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
%/2&.,1* the transmit signal is always prolonged by this time. In this case it corre-
sponds to a transient blocking following a reverse fault. This setting is only possible
via DIGSI
®
at Additional Settings.
In order to detect steady-state line faults such as open circuits, a monitoring time
'HOD\IRUDODUP is started when a fault is detected (address . Upon expira-
tion of this time the fault is considered a permanent failure. This setting is only possible
via DIGSI
®
at Additional Settings.
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