Siemens siprotec 7SA522, User Manual

Page: 303 / 628

Functions
6-155
7SA522 Manual
C53000-G1176-C119-2
Each individual cycle may also be blocked via binary input. In this case the cycle con-
cerned is declared as invalid and will is skipped in the sequence of permissible cycles.
If blocking takes place while the cycle concerned is already running, this leads to
aborting of the reclosure, i.e. no reclosure takes place even if other valid cycles have
been parameterized.
Internal blocking signals, with a limited duration, arise during the course of the reclose
cycles:
The blocking time
75(&/$,0
is initiated along with every automatic reclosure com-
mand. If the reclosure is successful, all the functions of the automatic reclosure return
to the quiescent state at the end of the blocking time; a fault after expiry of the reclaim
time is treated as a new fault in the network. Re-tripping by a protection function during
the reclaim time initiates the next reclose cycle in the case of multiple
reclosure; if no further reclosure is permitted, the last reclosure cycle is declared as
unsuccessful if re-tripping within the reclaim time takes place. The automatic
reclosure is blocked dynamically.
The dynamic blocking condition locks out the reclosure for the duration of the dynamic
blocking time (0.5 s). This occurs for example after a final trip or if other conditions
block the automatic reclosure function after starting has taken place. Restarting is
locked out for this time. When this time expires, the automatic reclosure function re-
turns to its quiescent state and is ready for a new fault in the power system.
If the circuit-breaker is closed manually (with the circuit breaker control switch via
a binary input, refer also to Subsection 6.17.1), the automatic reclosure is blocked for
a Manual–Close–blocking time
7%/2&.0&
. If a trip command is
issued during this time, it can be assumed that a metallic short-circuit is the cause (e.g.
closed earth switch). Every trip command within this time is therefore a final trip. With
the user definable logic functions (CFC) further control functions may also be treated
like a Manual–Close command.
Interrogation of
circuit-breaker
ready state A precondition for automatic reclosure following clearance of a short circuit is that the
circuit-breaker is ready for at least one BREAK–MAKE–BREAK–cycle when the auto-
matic reclosure circuit is started (i.e. at the time of the first trip command). The circuit
breaker ready state is signalled to the device via the binary input ">CB1 Ready" (FNo.
). If no such signal is available, the circuit-breaker interrogation (at the time of the
first trip) can be suppressed (presetting) as automatic reclosure would otherwise not
be possible at all.
In the event of a single cycle reclosure this interrogation is usually sufficient. Since, for
example, the air pressure or the spring tension for operation of the circuit-breaker
drops during the trip operation, no further interrogation should take place.
It is of advantage, particularly in the case of multiple reclosure, to interrogate the
readiness of the circuit-breaker not only at the time of the first trip command but also
before every reclosure . The reclosure is blocked as long as the CB does not signal it
is ready for another MAKE–BREAK–cycle.
The time needed by the circuit-breaker to regain the ready state can be monitored by
the 7SA522. This monitoring time
&%7,0(287
starts as soon as the CB indicates
the not ready state. The dead time may be extended if the ready state is not indicated
when it expires. However, if the circuit-breaker not ready state lasts longer than the
monitoring time, reclosure is blocked dynamically (refer also above to subtitle
"Reclose block", page 154).