4.134
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Group Settings (SET Command)
With this setting, the logic in the top of Figure 4.81 is operative. When an
open interval times out, the SEL
OGIC control equation reclose supervision
setting 79CLS is checked just once.
If 79CLS is asserted to logical 1 at the instant of an open interval time-out,
then the now-qualified open interval time-out propagates onto the final close
logic in Figure 4.81 to automatically reclose the circuit breaker.
If 79CLS is deasserted to logical 0 at the instant of an open interval time-out,
the following occurs:
➤ No automatic reclosing takes place.
➤ Relay Word bit RCSF (Reclose Supervision Failure indication)
asserts to logical 1 for one processing interval.
➤ If setting E79 := 1, 2, 3, or 4, the reclosing relay is driven to the
lockout state.
➤ If setting E79 := C1, C2, C3, or C4, the reclosing relay
increments the shot counter and starts timing on the next open
interval. This operation emulates a rotating drum timer style
reclosing relay—going on to the next open interval time and
reclose opportunity if supervising conditions for the present
reclose opportunity are not satisfied. If the reclosing relay
increments to the last shot value (no more open intervals left;
see Figure 4.86 and Tabl e 4.55), the reclosing relay is then
driven to the lockout state.
See Example 4.17.
For A Few, Unique Applications
Refer to the bottom of Figure 4.81 and Figure 4.82.
For a few unique applications, the Reclose Supervision Limit Time setting is
not set equal to zero seconds, e.g.,
79CLSD := 1.00 second
With this setting, the logic in the bottom of Figure 4.81 is operative. When an
open interval times out, the SEL
OGIC control equation reclose supervision set-
ting 79CLS is then checked for a time window equal to setting 79CLSD.
If 79CLS asserts to logical 1 at any time during this 79CLSD time window,
then the now-qualified open interval time-out propagates onto the final close
logic in Figure 4.80 to automatically reclose the circuit breaker.
If 79CLS remains deasserted to logical 0 during this entire 79CLSD time win-
dow, when the time window times out, the following occurs:
➤ No automatic reclosing takes place.
➤ Relay Word bit RCSF (Reclose Supervision Failure indication)
asserts to logical 1 for one processing interval.
➤ If setting E79 := 1, 2, 3, or 4, the reclosing relay is driven to
lockout state.
The logic in the bottom of Figure 4.81 is explained in more detail in the fol-
lowing text.
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