Siemens siprotec 7SA6, Manual

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Functions
6-197
7SA6 Manual
C53000-G1176-C156-2
Line A–B is tripped at both ends. There is therefore no voltage here, this identifies the
line at both ends as the faulted one. The normal dead time comes into service here.
Figure 6-103 Example of a reduced dead time (RDT)
Adaptive
Dead Time (ADT)
In all the previous alternatives it was assumed that defined and equal dead times were
set at both line ends, if necessary for different fault types and/or reclose cycles.
It is also possible to set the dead times (if necessary different for various fault types
and/or reclose cycles) at one line end only and to configure the adaptive dead time
(ADT) at the other end (or ends). This can be done on condition that the voltage trans-
formers are located on the line side of the circuit breaker or that means for the transfer
of a close command exist.
Figure 6-104 shows an example. It is assumed that the device
I
is operating with
defined dead times whereas the adaptive dead time is configured at position
II
. It is
important that the line is at least fed from busbar A, i.e. the side with the defined dead
times.
With the adaptive dead time the automatic reclosure function at line end
II
decides in-
dependently if and when reclosure is sensible and is therefore allowed and when it is
not. The criterion is the voltage on the line at end
II
, which is fed from end
I
following
reclosure there. Reclosure therefore takes place at end
II
as soon as it is apparent that
voltage has been re-applied to the line from end
I
.
In the illustrated case, the lines are tripped at positions I , II and III . At I reclosure takes
place after the dead time parameterized there. At III a reduced dead time can take
place (see above) if there is also an infeed on busbar B.
If the fault has been cleared (successful reclosure), line A–B is re-energised from bus-
bar A through position
I . Device II detects this voltage and also reclosed after a short
delay (to ensure a sufficient voltage measuring time). The system fault has ended.
If the fault has not been cleared after reclosure at
I
, a switch on to fault occurs at
I
, no
healthy voltage appear at
II
. The device there detects this and does not reclose.
In the case of multiple reclosure the sequence may be repeated several times follow-
ing an unsuccessful reclosure until one of the reclosures attempts is successful or a
final trip takes place.
Z1B
Z2
A, B, C busbars
I , II , III relay locations
tripped circuit-breakers
Z1
Z1B
Z2
Z1
A B C
I II III