6.24
SEL-311C Relay Instruction Manual Date Code 20060320
Close and Reclose Logic
Reclosing Relay
When reset timing starts again, the reset timer is fully loaded. Thus, successful
reset timing has to be continuous. Use the RSTMN Relay Word bit to monitor
reset timing (see Monitoring Open Interval and Reset Timing on page 6.16).
Settings Example 1
The block reset timing setting is:
79BRS = (51P + 51G) * 79CY
Relay Word bit 79CY corresponds to the Reclose Cycle State. The reclosing
relay is in one of the three reclosing relay states at any one time (see
Figure 6.5).
When the relay is in the Reset or Lockout State, Relay Word bit 79CY is
deasserted to logical 0. Thus, the 79BRS setting has no effect when the relay
is in the Reset or Lockout State. When a circuit breaker is closed from
lockout, there could be cold load inrush current that momentarily picks up a
time-overcurrent element (e.g., phase time-overcurrent element 51PT pickup
[51P] asserts momentarily). But, this assertion of pickup 51P has no effect on
reset timing because the relay is in the Lockout State (79CY = logical 0). The
relay will time immediately on reset time 79RSLD and take the relay from the
Lockout State to the Reset State with no additional delay because 79BRS is
deasserted to logical 0.
When the relay is in the Reclose Cycle State, Relay Word bit 79CY is asserted
to logical 1. Thus, the 79BRS setting can function to block reset timing if
time-overcurrent pickup 51P or 51G is picked up while the relay is in the
Reclose Cycle State. This helps prevent repetitive “trip-reclose” cycling.
Additional Settings Example 2
If the block reset timing setting is:
79BRS = 51P + 51G
then reset timing is blocked if time-overcurrent pickup 51P or 51G is picked
up, regardless of the reclosing relay state.
Sequence
Coordination
Setting (79SEQ)
The 79SEQ setting is applicable to distribution applications; for transmission
system applications set 79SEQ = 0. See the SEL-351 Instruction Manual for a
description of setting 79SEQ.
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