7SR11 & 7SR12 Description Of Operation
Chapter 1 Page 70 of 88 ©2017 Siemens Protection Devices Limited
The Relay goes to Lockout and the CB Alarm output is given where the DBI condition exists for longer than the
CB DBI Delay setting.
Hot Line In/Out
When ‘Hot Line’ is enabled all auto reclose sequences are inhibited and any fault causes an instantaneous trip to
lockout.
CB Open
CB Closed
&
&
&
&
CB Travel Alarm DTL
CB Alarm
≥1
CB Open
CB Closed
Figure 4-3 Logic Diagram: Circuit Breaker Status
79 Minimum LO Delay (Only in Auto-reclose models)
Sets the time that the Relay’s Lockout condition is maintained. After the last allowed Trip operation in a specific
sequence the Circuit Breaker will be left locked-out in the open position and can only be closed by manual or
remote SCADA operation. The 79 Minimum Lockout Delay timer can be set to delay a too-fast manual close
after lockout, this prevents an operator from manually closing onto the same fault too quickly and thus performing
multiple sequences and possibly burning-out Plant.
79 Reset LO by Timer(Only in Auto-reclose models)
Set to Enabled this ensures that the Lockout condition is reset when the timer expires, Lockout indication will be
cleared; otherwise, set to Disabled, the Lockout condition will be maintained until the CB is Closed by a Close
command.
Trip Time Alarm
The CB Trip Time meter displays the measured time between the trip being issued and the CB auxiliary contacts
changing state. If this measured time exceeds the Trip Time Alarm time, a Trip Time Alarm output is issued.
Trip Time Adjust
This allows for the internal delays caused by the relay – especially the delay before a binary input operates – to
be subtracted from the measured CB trip time. This gives a more accurate measurement of the time it took for the
CB to actually trip.
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