Date Code 20020215
Factory-Set Logic
1-31
SEL-351R Instruction Manual
S
EQUENCE
C
OORDINATION
Refer to subsection
Sequence Coordination Setting (79SEQ)
in
Section 6: Close and Reclose
Logic
for background on the operation of the 79SEQ setting.
See Figure 1.27. Enable sequence coordination with EZ setting:
Sequence coordination = Y (asserts Relay Word bit SEQC to logical 1)
Besides the Sequence coordination EZ setting, the factory-set sequence coordination logic
requires both the following be true:
•
SEL-351R is in the Reset state (Relay Word bit 79RS = logical 1)
•
Fast curve - phase or Fast curve - ground is picked up (Relay Word bit pickup indicator
51P1 = logical 1, 51G1 = logical 1, or 51N1 = logical 1, respectively)
Then the sequence coordination SEL
OGIC
setting 79SEQ asserts to logical 1.
Relay
Word
Bits
79RS
51P1
51G1
51N1
reset state
phase
ground
sequence coordination enabled with
setting ESEQ (or corresponding EZ
setting Sequence coordination)
SEQC
fast phase or ground
curve picked up
SEL
OGIC
Setting
79SEQ
(input into
sequence
coordination
logic)
DWG: M351R027
Figure 1.27: Sequence Coordination Logic
Refer to the example in Figure 1.28. The sequence coordination logic in Figure 1.27 keeps
SEL-351R(1) from overtripping for a fault beyond SEL-351R(2).
Refer to Figure 1.29. The following are factory settings for SEL-351R(1):
79SEQ = 79RS * (51P1 + 51G1 + 51N1) * SEQC
51P1TC = !SV8 * OCP
(see Figure 1.2 and Figure 1.15)
Presuming the cold load pickup scheme is not active, !SV8 = NOT(SV8) = NOT (logical 0) =
logical 1. Setting 51P1TC is then controlled only by Relay Word bit OCP. With factory EZ
setting Operations - phase fast curve = 2, Relay Word bit OCP = logical 1 for shot counter = 0
and shot counter = 1. Fast curve - phase (51P1T) is then enabled for shot counter = 0 and shot
counter = 1.
Figure 1.29 gives a time-line of the operation of SEL-351R(1) sequence coordination logic for a
fault beyond downstream SEL-351R(2). Each time SEL-351R(2) interrupts the phase fault, the
SEL-351R(1) shot counter increments to the next shot. The shot counter in turn controls Fast
curve - phase (51P1T) via torque control setting 51P1TC.
Once shot counter = 2, Fast curve - phase is disabled. Then when downstream SEL-351R(2) is
operating on Delay curve - phase, the SEL-351R(1) Fast curves are out of the way—the
SEL-351R(1) does not overtrip for a fault beyond SEL-351R(2).
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