Date Code 20010731
Breaker Logic
3-15
SEL-352-1, -2 Instruction Manual
Setting Description
Trip Inputs (TRIPA, TRIPB, TRIPC)
Use
SET G <ENTER>
to associate the breaker failure initiate logic inputs (TRIPA, TRIPB,
TRIPC) with physical inputs.
Any optoisolated input can be used to control the logic inputs. For example, if IN101 is used to
initiate an A-phase breaker fail condition from the protective relay, set TRIPA = IN101. Repeat
this for each trip input. The same input may be used for all three trip input conditions if single-
pole tripping is not used. The trip input settings are actually SEL
OGIC
control equations. Use
any combination of Relay Word bits according to the SEL
OGIC
control equation criterion in
Section 5: Control Logic
.
Fault Detector (50FT)
Range:
0.50–45.00 A in 0.01-A steps (5 A)
0.10–9.00 A in 0.01-A steps (1 A)
Use
SET <ENTER>
to access the 50FT setting, needed for all fault condition breaker failure
schemes. This setting selection is based on the minimum fault current for which the scheme
must operate. The fault current logic operates each time the breaker is called on to trip phase
current greater than the 50FT setting. Note that the 50FT setting for Scheme 4 must be greater
than the maximum load current. The 50FT element is the only overcurrent element that includes
the subsidence current logic discussed earlier in this section.
The SEL-352 Relay does not discriminate between phase faults and ground faults. Fault
discrimination is based strictly on phase current magnitude. Breaker operations for ground faults
with current duties above the 50FT setting are protected under the failure-to-break fault current
logic. A separate 50N fault detector is available for customizing your scheme.
RMS Overcurrent (50RMS) (SEL-352-2 Relay)
Range:
0.50–45.00 A in 0.10-A steps
0.10–9.00 A in 0.02-A steps
Use the 50RA, 50RB, 50RC, or 50R elements to detect an RMS overcurrent condition on a
per-pole or three-phase basis. The 50R elements can be used to block tripping when the RMS
current exceeds some percentage of the maximum interrupt rating for the breaker. You may then
transfer the trip to adjacent breakers with higher fault duty.
Set 50RMS to the value at which the element should pick up. See Figure 3.16. This feature is
only available in the SEL-352-2 Relay.
Содержание SEL-352-1
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