Functions
6-126 7SA6 Manual
C53000-G1176-C133-1
Figure 6-74 Logic diagram of the unblocking scheme (one line end)
6.6.1.3 Directional Blocking Scheme
Principle In the case of the blocking scheme, the transmission channel is used to send a block
signal from one line end to the other. The signal transmission is started as soon as a
fault in reverse direction is detected, optionally also right after fault inception (jump
detector via dashed line). It is stopped as soon as the earth fault protection detects a
fault in forward direction, alternatively the signal is only sent when the earth fault
protection detects the fault in the reverse direction. On the other hand the signal will
be maintained if the fault is in reverse direction. If the signal is sent with jump
detections (i. e. ()7HOH%/-XPS is routed in parallel with ()7HOH
6(1'), only a short delay to allow for signal transmission is required before the
directional E/F trips. Tripping is possible with this scheme even if no signal is received
from the opposite line end. It is therefore mainly used for long lines when the signal
must be transmitted across the protected feeder by means of power line carrier (PLC)
and the attenuation of the transmitted signal at the fault location may be so severe that
reception at the other line cannot necessarily be guaranteed.
In Figure 6-75 the operation scheme is shown.
Earth faults in the forward direction cause tripping if a blocking signal is not received
from the opposite line end. Due to possible differences in the pick up time delays of
the devices at both line ends and due to the signal transmission time delay, the tripping
must be somewhat delayed by T
V
in this case.
To avoid signal race conditions, a transmit signal can be prolonged by the settable
time T
S
once it has been initiated.
EF Pickup
&
EF forward
6HQG3URORQJ
T0
&
≥1
&
Trip command
&
Transient blocking
&
≥1
&
≥1
≥1
100100020
ms ms
>EF UB ub 1
&
&
&
&
Two terminals
Three terminals
Two terminals
Three terminals
„1“
/LQH&RQILJ
Two terminals
Three terminals
≥1
≥1
&
&
≥1
≥1
EF Telep. off
1313
>EF TeleprotBLK
1320
>EF UB bl 1
1321
>EF UB bl 2
1323
>EF UB ub 2
1322
EF Telep. OFF
1381
EF Tele SEND
1384
Echo function
section 6.6.1.5
EF Enable Trip
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