3-40 Breaker Logic Date Code 20010731
SEL-352-1, -2 Instruction Manual
Phase Current Unbalance Ratio (46UB)
Range: 8, 16, 32, 64
Use SET <ENTER> to access the 46UB setting. This setting defines the divisor the relay uses
to determine whether an unbalance exists between the three-phase current magnitudes.
Phase Current Unbalance Enable (UBLOG)
Range: OFF, ON, CUSTOM
Use SET <ENTER> to access the UBLOG setting. Enable, modify, or disable the phase current
unbalance logic to detect open conductors.
Set UBLOG = ON to enable the phase current unbalance logic. If you do not need phase current
unbalance logic, set UBLOG = Off. If you need logic for your application different from that
available with the default logic, set UBLOG=CUSTOM and modify logic settings to meet your
specific application needs.
Close Input (UCpu)
Range: 0–16383 cycles in 1/4-cycle steps
Use SET <ENTER> to access the UCpu setting and define the close input timer pickup time.
Set the UCpu timer higher than the nominal closing time of the protected breaker. The timer
may be set the same as the SlowCl setting. A recommended setting is 125 percent to 150 percent
of timing tests. For the example breaker, assuming a closing time of four cycles, we select a
setting:
UCpu = 6 cycles
The margin, in this case an additional two cycles, allows for possible pole scatter upon closure.
Unbalance Pending Failure (UPpu)
Range: 0–16383 cycles in 1/4-cycle steps
Use SET <ENTER> to access the UPpu setting and define the pending failure timer pickup
time.
Set the current unbalance pending failure timer (UPpu) shorter than the UFpu setting. A
recommended setting is UPpu = 50 cycles. The setting for UPpu is based on the breaker trip
time and the time calculated for UFpu. If you use the UPpu to trip the breaker, the UBPF bit
should assert in enough time to let the breaker trip before tripping the lockout relay with the
UBBF bit. The recommended setting for UPpu is the UFpu time minus the nominal breaker trip
time and some margin.
To Next Page
