4-42
Protection and Control
BE1-951
7 9 R T D
7 9 R T D
7 9 R T D
7 9 R T D
7 9 R T D
R E S E T
791TD
792TD
793TD
794TD
L O C K O U T
R E S E T
Manual Close
1
2
3
4
5
1
1
2
3
4
5
1
Closed
B R E A K E R S T A T U S
Open
R E S E T
T I M E R
79C
S C B
S T E P
7 9 S C B
D2635-09
03-27-98
Figure 4-23. S#-79SCB=1/2/3/4/5 Logic Timing Diagram
79RTD
79RTD
79RTD
79RTD
79RTD
RESET
791TD
792TD
793TD
794TD
LOCKOUT
RESET
Manual Close
1
2
3
4
5
1
1
2
3
4
5
1
Closed
BREAKER STATUS
Open
RESET
TIMER
79C
SCB
STEP
79SCB
D2635-10
11-29-98
Figure 4-24. S#-79SCB=2/3/4/5 Logic Timing Diagram
step list = step number(s).
A forward slash can be used between numbers if more than
one condition is required. (Example S1-79SCB=1/2/3). See Table 4-30 for S<g>-79SCB
settings information.
S<g>-79SCB Command Example
1. Program the 79SCB output to be TRUE except during Reset and Lockout for all setting groups.
Figure 4-23 illustrates the logic timing diagram for this example.
>S#-79SCB=2/3/4/5
Figure 4-23 shows a logic timing diagram showing all possible sequence control blocks enabled (TRUE).
In Figure 4-24, 79RTD is the reclose reset time delay and 79#TD is the reclose time delay where # is the
reclose shot number.
Zone Sequence Coordination
To coordinate tripping and reclosing sequences with downstream protective relays and reclosers, the
BE1-951 senses fault current from downstream faults when a user programmable logic, set by the SP-
79ZONE command, picks up and then drops out without a trip output (defined with the SG-TRIGGER
command) occurring. Typically, the low-set instantaneous pickup outputs (50TPPU and 50TNPU) or the
time-overcurrent pickup outputs (51PPU and 51NPU) are used for the zone sequence settings
(SP-79ZONE = 50TNPU or SP79ZONE = 51PPU+51NPU).
If the upstream relay (BE1-951) senses that fault current has been interrupted by a downstream device, the
BE1-951 will increment the trip/reclose sequence by one operation. This occurs because the BE1-951
