2.15 Automatic Reclosure Function (optional)
295
7SD5 Manual
C53000-G1176-C169-1
Figure 2-123 Example of adaptive dead time (ADT)
As is shown by the example, the adaptive dead time has the following advantages:
• The circuit breaker at position II is not reclosed at all if the fault persists and is not
unnecessarily stressed as a result.
• With non-selective tripping on an external fault by an overreaching time-graded pro-
tection, no further auto-reclosure attempts can be generated there because the fault
current path via busbar B and position II remains interrupted even after several re-
closure attempts.
• At position I overreach is allowed in the case of multiple reclosures and even in the
event of final tripping because the line remains open at position II and therefore no
actual overreach can occur at I.
CLOSE-Command
Transmission
(Remote-CLOSE)
With close command transmission, the dead times are only set at one line end. The
other (or the others in lines with more than two ends) are set to „Adaptive Dead Time
(ADT)“. The latter only react to the received close commands from the transmitting
end. An adaptive dead time is thus possible even without a voltage.
At the sending line end, the trasmission of the close command is delayed until it is sure
that the local reclosure was successful. This means that after reclosure still a possible
local pickup is waited for. This delay prevents unnecessary closing at the remote end
on the one hand but also increases the time until reclosure takes place there. This is
not critical for a single-pole interruption or in radial or meshed networks if no stability
problems are expected under these conditions.
The existing protection data interfaces are used to transmit the close command.
Connecting an Ex-
ternal Auto-Reclo-
sure Device
If the 7SD5 has to work with an external reclosure device, the binary inputs and
outputs provided for this purpose must be taken into consideration. The following
inputs and outputs are recommended:
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