4.143
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
Reset Timer
The reset timer qualifies circuit breaker closure before taking the relay to the
reset state from the reclose cycle state or the lockout state. Circuit breaker sta-
tus is determined by the SEL
OGIC control equation setting 52A. (See Trip/
Close Logic on page 4.128 for more discussion on SEL
OGIC control equation
setting 52A.
Setting 79RSD. Qualifies closures when the relay is in the reclose cycle
state. These closures are usually automatic reclosures resulting from open
interval time-out.
It is also the reset time that the sequence coordination schemes (see Sequence
Coordination Setting (79SEQ) on page 4.150) use.
Setting 79RSLD. Qualifies closures when the relay is in the lockout state.
These closures are usually manual closures. These manual closures can
originate external to the relay, via the CLOSE command, or via the SEL
OGIC
control equation setting CL (see Figure 4.80).
Setting 79RSLD is also the reset timer the relay uses when it powers up, has
individual settings changed for the active setting group, or the active setting
group is changed (see Reclosing Relay States and Settings/Setting Group
Changes on page 4.140).
Typically, setting 79RSLD is set less than setting 79RSD. Setting 79RSLD
emulates reclosing relays with motor-driven timers that have a relatively short
reset time from the lockout position to the reset position.
The 79RSD and 79RSLD settings are set independently (setting 79RSLD can
even be set greater than setting 79RSD, if desired). SEL
OGIC control equation
setting 79BRS (block reset timing) can be set to control reset timing (see
Block Reset Timing Setting (79BRS) on page 4.149).
Monitoring Open Interval and Reset Timing
Open interval and reset timing can be monitored with the following Relay
Word bits:
If the open interval timer is actively timing, OPTMN asserts to logical 1.
When the relay is not timing on an open interval (e.g., it is in the reset state or
in the lockout state), OPTMN deasserts to logical 0. The relay can only time
on an open interval when it is in the reclose cycle state, but just because the
relay is in the reclose cycle state does not necessarily mean the relay is timing
on an open interval. The relay only times on an open interval after successful
reclose initiation and no stall conditions are present (see Skip Shot (79SKP)
and Stall Open Interval Timing (79STL) Settings on page 4.147).
If the reset timer is actively timing, RSTMN asserts to logical 1. If the reset
timer is not timing, RSTMN deasserts to logical 0. See Block Reset Timing
Setting (79BRS) on page 4.149.
Relay Word Bits Definition
OPTMN Indicates that the open interval timer is actively timing
RSTMN Indicates that the reset timer is actively timing
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