Schweitzer Engineering Laboratories SEL-351A, Руководство пользователя

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6.26
SEL-351A Relay Instruction Manual
Date Code 20080213
Close and Reclose Logic
Reclosing Relay
Additional Settings Example 2
If the block reset timing setting is:
79BRS = 51P + 51G
then reset timing is blocked if time-overcurrent pickup 51P or 51G is picked
up, regardless of the reclosing relay state.
Sequence
Coordination Setting
(79SEQ)
The sequence coordination setting 79SEQ keeps the relay in step with a
downstream line recloser in a sequence coordination scheme, which prevents
overreaching SEL-351A overcurrent elements from tripping for faults beyond
the line recloser. This is accomplished by incrementing the shot counter and
supervising overcurrent elements with resultant shot counter elements.
In order for the sequence coordination setting 79SEQ to increment the shot
counter,
both the following conditions must be true:
➤
No trip present (Relay Word bit TRIP = logical 0)
➤
Circuit breaker closed (SEL
OGIC
control equation setting
52A = logical 1, effectively)
The sequence coordination setting 79SEQ is usually set with some overcurrent
element pickups. If the above two conditions are both true, and a set
overcurrent element pickup asserts for at least 1.25 cycles and then deasserts,
the shot counter increments by one count. This assertion/deassertion indicates
that a downstream device (e.g., line recloser—see
Figure 6.8 ) has operated to
clear a fault. Incrementing the shot counter keeps the SEL-351A “in step”
with the downstream device, as is shown in the following
Additional Settings
Example 1 and Additional Settings Example 2 .
Every time a sequence coordination operation occurs, the shot counter is
incremented, and the reset timer is loaded up with reset time 79RSD.
Sequence coordination can increment the shot counter beyond last shot, but no
further than shot = 4. The shot counter returns to shot = 0 after the reset timer
times out. Reset timing is subject to SEL
OGIC
control equation setting 79BRS
[see Block Reset Timing Setting (79BRS) on page 6.25 ].
Sequence coordination operation does not change the reclosing relay state. For
example, if the relay is in the Reset State and there is a sequence coordination
operation, it remains in the Reset State.
Factory Settings Example
Sequence coordination is not enabled in the factory settings:
79SEQ =
0
Additional Settings Example 1
With sequence coordination setting:
79SEQ = 79RS * 51P
sequence coordination is operable only when the relay is in the Reset State
(79RS = logical 1). Refer to
Figure 6.8 and Figure 6.9 .
Courtesy of NationalSwitchgear.com