Date Code 20010515
Specifications
2-15
SEL-2BFR, -2/BFR Instruction Manual
When the trip input is asserted, the 62FC pickup timer starts. If 50FT is asserted when the 62FC
timer expires, the Relay Word FBF bit asserts. If the trip input is deasserted or the 50FT element
drops out before 62FC expires, the logic resets and FBF does not assert.
This scheme is similar to Scheme 3 because the trip input must remain asserted while current still
flows in the protected breaker.
Figure 2.5: A-Phase Failure to Trip for Fault Logic, Scheme 5
Scheme 6
Figure 2.6 illustrates Scheme 6 A-phase and three-phase breaker protection. Use Scheme 6
breaker protection in single breaker, ring-bus, or breaker-and-a-half installations.
When the SEL-2BFR Relay trip input is asserted, the 62TT pickup timer starts. The trip input is
latched and may be deasserted after a single quarter-cycle assertion. Following trip input
assertion and 62TT pickup time, the 62TT timer output asserts. The timer output remains
asserted for one cycle. Relay Word bit FBF asserts if 50FT picks up and asserts during the one-
cycle window.
DWG: IM2006
DATE: 06-07-00
50FT
OR
2
RELAY OR
MANUAL TRIPS
AND
1
TRIP A
TRIP B
TRIP C
OR
1
1CY
62FC
FCpu
THREE-POLE
SINGLE-POLE
. . . TO B-PHASE AND C-PHASE LOGIC
1CY
62TT
TTpu
TIMEOUT A (TIMEOUT A=0 -- SWITCH OPEN;
TIMEOUT A=1 -- SWITCH CLOSED)
TRIP A
IA
SWITCH
RELAY OR
MANUAL TRIP
FBF
A-PHASE LOGIC SHOWN
B-PHASE AND C-PHASE LOGIC SIMILAR
FROM B-PHASE LOGIC . . .
FROM C-PHASE LOGIC . . .
Figure 2.6: A-Phase and Three-Phase Failure to Trip for Fault Logic, Scheme 6
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