6.25
Date Code 20080213
Instruction Manual
SEL-351A Relay
Close and Reclose Logic
Reclosing Relay
Other Settings Considerations
If no special skip shot or stall open interval timing conditions are desired,
make the following settings:
79SKP =
0
(numeral 0)
79STL =
0
(numeral 0)
Block Reset Timing
Setting (79BRS)
The block reset timing setting 79BRS keeps the reset timer from timing.
Depending on the reclosing relay state, the reset timer can be loaded with
either reset time:
79RSD (Reset Time from Reclose Cycle)
or
79RSLD (Reset Time from Lockout)
Depending on how setting 79BRS is set, none, one, or both of these reset
times can be controlled. If the reset timer is timing and then 79BRS asserts to:
79BRS = logical 1
reset timing is stopped and does not begin timing again until 79BRS deasserts
to:
79BRS = logical 0
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 6.17
Factory Settings Example
The block reset function is not enabled in the factory settings:
79BRS =
0
(numeral 0)
Additional 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
When the relay is in the Reset or Lockout States, 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 States. 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 factory 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.
Summary of Contents for SEL-351A
Page 10: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 16: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 34: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 126: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 184: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 198: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 228: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 278: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 384: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 410: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 450: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 454: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 472: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 504: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 558: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 562: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 586: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 608: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 666: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...