Schweitzer Engineering SEL-351P, Quick Start Manual

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1-38 Factory-Set Logic Date Code 990215
SEL-351P Manual Técnico
Refer to the example in Figure SECTION 1: .28. The sequence coordination logic in Figure
SECTION 1: .27 keeps SEL-351P(1) from overtripping for a fault beyond SEL-351P(2).
Refer to Figure SECTION 1: .29. The following are factory settings for SEL-351P(1):
79SEQ = 79RS * (51P1 + 51G1 + 51N1) * SEQC (see Figure SECTION 1: .27)
51P1TC = !SV8 * OCP (see Figure SECTION 1: .2 and
Figure SECTION 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 SECTION 1: .29 gives a time-line of the operation of SEL-351P(1) sequence
coordination logic for a fault beyond downstream SEL-351P(2). Each time SEL-351P(2)
interrupts the phase fault, the SEL-351P(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-351P(2) is
operating on Delay curve - phase, the SEL-351P(1) Fast curves are out of the way – the
SEL-351P(1) does not overtrip for a fault beyond SEL-351P(2).
As stated in subsection Sequence Coordination Setting (79SEQ) in Section 6: Close and
Reclose Logic , the reset timer setting 79RSD (corresponding EZ setting Reset time for auto
reclose) takes the shot counter back to shot counter = 0 after a sequence coordination operation
increments the shot counter. Make sure that reset timer setting 79RSD is set long enough to
maintain the shot counter at shot = 2 as shown in Figure SECTION 1: .29.
Other sequence coordination details involving ground elements:
•
If setting Min. trip - ground is set below 0.1 Amp secondary, 51N1 provides the
indication that the ground fault current is above the normal Min. trip - ground setting
value and the Fast curve - ground is picked up (51G1 is turned off automatically).
Otherwise, 51G1 provides the indication (51N1 is turned off automatically).