Schweitzer Engineering Laboratories SEL-351A, Manual

Page: 214 / 666

6.16
SEL-351A Relay Instruction Manual
Date Code 20080213
Close and Reclose Logic
Reclosing Relay
Open Interval Timers
The reclose enable setting, E79, determines the number of open interval time
settings that can be set. For example, if setting E79 = 3 or C3, the first three
open interval time settings in
Table 6.2 , are made available for setting.
If an open interval time is set to zero, then that open interval time is not
operable,
and neither are the open interval times that follow it.
In the factory settings in Table 6.2 , the open interval 2 time setting 79OI2 is
the first open interval time setting set equal to zero:
79OI2 =
0.00 cycles
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 cycles
79OI3 =
900.00 cycles
(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., 79OI3 = 0.00).
If open interval 1 time setting, 79OI1, is set to zero (79OI1 = 0.00 cycles), 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 = 30.00
cycles, and 79OI2 = 600.00 cycles, open interval 1 time setting, 79OI1, times
first. If the 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 6.6 .
Figure 6.6 Reclosing Sequence From Reset to Lockout With Example Settings
SEL
OGIC
control equation setting 79STL (stall open interval timing) can be
set to control open interval timing [see Skip Shot and Stall Open Interval
Timing Settings (79SKP and 79STL, respectively) on page 6.23 ].
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 above example settings, two set open interval times precede open
interval 3 time, which is set to zero (79OI3 = 0.00):
79OI1 =
30.00
Open Interval Time-out
Shot
Counter
0
52A
79OI1 = 30
Reset State
Trip Close Trip Close Trip
Reclose Cycle State Lockout State
(79OI3 = 0)
79OI2 = 600
(Last Shot = 2)
1 2
Courtesy of NationalSwitchgear.com