Siemens siprotec 7SA522, User Manual

Page: 262 / 628

Functions
6-114
7SA522 Manual
C53000-G1176-C119-2
6.6.1 Method of Operation
Switching On and
Off The teleprotection function can be switched on and off by means of the parameter
)&77HOHS()
, or via the system interface (if available) and via binary input
(if this is allocated). The switched state is saved internally (refer to Figure 6-64) and
secured against loss of auxiliary supply. It is only possible to switch on from the source
where previously it had been switched off from. To be active, it is necessary that the
function is switched on from all three switching sources.
X
Figure 6-64 Switching on and off of the signal transmission logic
6.6.1.1 Directional Comparison Scheme
Principle The directional comparison scheme is a permissive scheme. In Figure 6-65 the
oper-
ation scheme
is shown.
When the earth fault protection recognizes a fault in the forward direction, it initially
sends a permissive signal to the opposite line end. If a permissive signal is also re-
ceived from the remote end, the trip signal is passed on to the tripping relay. Accord-
ingly it is a prerequisite for fast tripping that the fault is recognized in the forward direc-
tion at both line ends.
The send signal can be prolonged by T
S
(parameter setting). The prolongation of the
send signal only comes into effect if the protection has already issued a trip command.
This ensures that the permissive signal releases the opposite line end even if the earth
fault is very rapidly cleared by a different independent protection.
Figure 6-65 Operation scheme of the directional comparison method
≥
1
EF TeleprotOFF
EF Telep. OFF
ON
OFF
)&77HOHS()
EF Teleprot.ON
S
R
System port: EF Telep. OFF
S
R
„1“
System port: EF Telep. ON
rec.
transm.
A B
E/F.
frwd.
T
S
&
trip
rec.
&
≥
1
E/F.
frwd.
T
S
&
trip
transm
&
≥
1