Siemens siprotec 7SA6 User Manual page 353

Interrogation of
Circuit-Breaker
Ready
Processing the
Circuit Breaker
Auxiliary Contacts
7SA6 Manual
C53000-G1176-C133-1
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 reclaim time 75(&/$,0 is initiated along with every automatic reclosure
command. If the reclosure is successful, all the functions of the automatic reclosure
return to the quiescent state at the end of the reclaim 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
returns 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 discrepancy
switch via a binary input, refer also to Subsection 6.20.1), 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.
A precondition for automatic reclosure following clearance of a short-circuit is that the
circuit breaker is ready for at least one TRIP–CLOSE–TRIP–cycle when the automatic
reclosure 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 "!&% 5HDG\" (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-shot 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 CLOSE–TRIP–cycle.
The recovery time of the circuit-breaker can be monitored by the 7SA6. 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 6-
170).
If the circuit-breaker auxiliary contacts are connected to the device, a plausibility check
of the circuit-breaker response is also carried out.
In the case of single-pole tripping this applies to each individual breaker poles. A
precondition for this is that the auxiliary contacts must be connected to the appropriate
Functions
6-171