Schweitzer Engineering Laboratories SEL-751 - Figure 4.85 Reclosing Sequence from Reset to Lockout with Example Settings

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SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Group Settings (SET Command)
Thus, open interval times 79OI2, 79OI3, and 79OI4 are not operable. In the
factory settings, both open interval times 79OI3 and 79OI4 are set to zero. But
if the settings were:
79OI2 := 0.00 seconds
79OI3 := 15.00 seconds (set to some value other than zero)
open interval time 79OI3 would still be inoperative, because a preceding open
interval time is set to zero (i.e., 79OI2 := 0.00).
If open interval 1 time setting, 79OI1, is set to zero (79OI1 := 0.00 seconds),
no open interval timing takes place, and the reclosing relay is defeated.
The open interval timers time consecutively; they do not have the same
beginning time reference point. For example, with settings 79OI1 := 0.50, and
79OI2 := 10.00, open interval 1 time setting, 79OI1, times first. If subsequent
first reclosure is not successful, then open interval 2 time setting, 79OI2, starts
timing. If the subsequent second reclosure is not successful, the relay goes to
the lockout state. See the example time line in Figure 4.85.
Figure 4.85 Reclosing Sequence From Reset to Lockout With Example Settings
SELOGIC control equation setting 79STL (stall open interval timing) can be
set to control open interval timing (see Skip Shot (79SKP) and Stall Open
Interval Timing (79STL) Settings on page 4.147).
Determination of Number of Reclosures (Last Shot)
The number of reclosures is equal to the number of open interval time settings
that precede the first open interval time setting set equal to zero. The “last
shot” value is also equal to the number of reclosures.
In the previous example settings, two set open interval times precede open
interval 3 time, which is set to zero (79OI3 := 0.00):
79OI1 := 0.50
79OI2 := 10.00
79OI3 := 0.00
For this example:
Number of reclosures (last shot) = 2 = the number of set open interval
times that precede the first open interval set to zero.
Observe Shot Counter Operation
Observe the reclosing relay shot counter operation, especially during testing,
using ASCII command TARGET (e.g., TARGET Command (Display Relay
Word Bit Status) on page 7.53 for detail).
Open Interval Time-out
Shot
Counter
0
52A
79OI1 = 0.5
Reset State
Trip Close Trip Close Trip
Reclose Cycle State Lockout State
(79OI3 = 0)
79OI2 = 10.0
(Last Shot = 2)
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