Blocking - Siemens SIPROTEC 7SJ62 Manual

2.14.2

Blocking

Static Blocking
Static blocking means that the automatic reclosing system is not ready to initiate reclosing, and cannot initiate
reclosing as long as the blocking signal is present. A corresponding message „79 is NOT ready" (FNo.
2784) is generated. The static blocking signal is also used internally to block the protection elements that are
only supposed to work when reclosing is enabled (see also side title "Reclosing Before Selectivity" further
above).
The automatic reclosing system is statically blocked if:
• The signal „>BLOCK 79" FNo.2703) is present at a binary input, as long as the automatic reclosing system
is not initiated (associated message: „>BLOCK 79"),
• The signal „>CB Ready" (FNo. 2730) indicates that the circuit breaker disappears via the binary input, if
the automatic reclosing system is not initiated (associated message: „>CB Ready"),
• The number of allowable reclosing attempts set for both reclosing programs is zero (associated message:
„79 no cycle"),
• No protective functions (parameters 7150 to 7163) or binary inputs are set to initiate the automatic reclosing
system (associated message: „79 no starter"),
• The circuit breaker position is reported as being "open" and no trip command applies (associated message:
„79 BLK: CB open"). This presumes that 7SJ62/64 is informed of the circuit breaker position via the aux-
iliary contacts of the circuit breaker.
Dynamic Blocking
Dynamic blocking of the automatic reclosing program occurs in those cases where the reclosing program is
active and one of the conditions for blocking is fulfilled. The dynamic blocking is signaled by the message „79
DynBlock". The dynamic blocking is associated with the configurable blocking time SAFETY 79 ready. This
blocking time is usually started by a blocking condition that has been fulfilled. After the blocking time has
elapsed, the device checks whether or not the blocking condition can be reset. If the blocking condition is still
present or if a new blocking condition is fulfilled, the blocking time is restarted. If, however, the blocking condi-
tion no longer holds after the blocking time has elapsed, the dynamic blocking will be reset.
Dynamic blocking is initiated if:
• The maximum number of reclosure attempts has been achieved. If a trip command now occurs within the
dynamic blocking time, the automatic reclosure program will be blocked dynamically, (indicated by „79
Max. No. Cyc").
• The protection function has detected a three-phase fault and the device is programmed not to reclose after
three-phase faults, (indicated by „79 BLK:3ph p.u.").
• if the maximum waiting period T DEAD DELAY for the delay of the dead time initiation by binary inputs
expires without binary input „>79 DT St.Delay" having been disabled during this time period.
• The action time has elapsed without a TRIP command being issued. Each TRIP command that occurs after
the action time has expired and before the picked-up element drops out, will initiate the dynamic blocking
(indicated by „79 Tact expired").
• A protective function trips which is to block the automatic reclosure function (as configured). This applies
irrespective of the status of the automatic reclosure system (started / not started) if a TRIP command of a
blocking element occurs (indicated by „79 BLK by trip").
• The circuit breaker failure function is initiated.
• The circuit breaker does not trip within the configured time T-Start MONITOR after a trip command was
issued, thus leading to the assumption that the circuit breaker has failed. (The breaker failure monitoring is
primarily intended for commissionnig purposes. Commissionnig safety checks are often conducted with the
circuit breaker disconnected. The breaker failure monitoring prevents unexpected reclosing after the circuit
breaker has been reconnected, indicated by „79 T-Start Exp").
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
Functions
2.14 Automatic Reclosing System 79
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