4.1.2 Auto Reclose Sequences; Figure 4.1-1 Typical Auto Reclose Sequence With 3 Instantaneous And 1 Delayed Trip - Siemens 7SR21 Manual

4.1.2 Auto Reclose sequences

The CONTROL & LOGIC>AUTO RECLOSE PROT'N and CONTROL & LOGIC>AUTORECLOSE CONFIG'
menus, allow the user to set independent Protection and Auto Reclose sequences for each type of fault i.e. Phase
Fault (P/F), Derived/Measured Earth Fault (E/F), Sensitive Earth Fault (SEF) or External Protections (EXTERN).
Each Auto Reclose sequence can be user set to up to four-shots i.e. five trips + four reclose sequence, with
independently configurable type of Protection Trip. Overcurrent and earth fault elements can be assigned to any
combination of Fast (Inst), Delayed or highset (HS) trips. Deadtime Delay time settings are independent for
each AR shot. The user has programming options for Auto Reclose Sequences up to the maximum shot count
i.e.:-
Inst or Delayed Trip 1 + (DeadTime 1: 0.1s-14400s)
+ Inst or Delayed Trip 2 + (DeadTime 2: 0.1s-14400s)
+ Inst or Delayed Trip 3 + (DeadTime 3: 0.1s-14400s)
+ Inst or Delayed Trip 4 + (DeadTime 4: 0.1s-14400s)
+ Inst or Delayed Trip 5 – Lockout.
The AR function recognizes developing faults and, as the shot count advances, automatically applies the correct
type of Protection and associated Dead time for that fault-type at that point in the sequence.
A typical sequence would consist of two Inst trips followed by at least one Delayed trip. This sequence enables
transient faults to be cleared quickly by the Inst trip(s) and permanent fault to be cleared by the combined
Delayed trip. The delayed trip must be 'graded' with other Recloser/CB's to ensure system discrimination is
maintained, ie. that as much of the system as possible is live after the fault is cleared.
A HS trips to lockout setting is provided such that when the number of operations of elements assigned as HS
trips reach the setting the relay will go to lockout.
The number of Shots (Closes) is user programmable, note: - only one Shot Counter is used to advance the
sequence, the Controller selects the next Protection characteristic/Dead time according to the type of the last Trip
in the sequence e.g. PF, EF, SEF or EXTERNAL.
Reclose Dead Time
User programmable dead times are available for each protection trip operation.
The dead time is initiated when the trip output contact reset, the pickup is reset and the CB is open.
The CB close output relay is energised after the dead time has elapsed.
st
1 Trip (Inst)
st
1 Dead Time

Figure 4.1-1 Typical Auto Reclose Sequence with 3 Instantaneous and 1 Delayed trip

©2010 Siemens Protection Devices Limited
rd
nd
2 Trip (Inst) 3 Trip (Inst)
nd
2 Dead Time
3
7SR21 & 7SR22 Argus Description of Operation
th
4 Trip (Delayed)
rd
th
Dead Time
4 Dead Time
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