6–92 345 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
S4 CONTROLS CHAPTER 6: SETPOINTS
Winding breaker failure
There are two Breaker Failure functions, one per winding breaker. The BF function monitors
the phase currents after a trip command from a protection element is initiated. If any
phase current is above the set current level after the BF DELAY timer/timers expire, a
Breaker Failure will be declared, and will operate the selected output relays. The Breaker
Failure scheme also provides the setup for BF initiate from the external input via Contact
Input, Virtual Input, Remote Input, or Logic Element.
The operation of the filter that reduces the overreaching effect of the assymetrical offset
currents will cause the measured current to ramp down to zero after the breaker trips. It is
strongly recommended that a margin of 1.5 power cycle time is added to the expected
breaker time-to-trip time for the BF DELAY1 and BF DELAY 2 timers.
NOTE:
W1 BREAKER FAIL logic is triggered only upon operation of a protection element with a
function set to Trip, and the CT INPUT associated with Winding 1 CT - i.e. CT(W1). Similarly,
the W2 BREAKER FAIL logic will be triggered only upon operation of a protection element
with the function set to Trip, and the CT INPUT set to CT(W2).
When the 345 relay allows the configuration of only one breaker failure function, this
function is always associated with the Winding 1 breaker, and will be triggered upon
operation of any protection element with a FUNCTION setting set to Trip, and the CT INPUT
set to CT(W1).
The following path is available using the keypad. For instructions on how to use the
keypad, please refer to Chapter 3 - Working with the Keypad.
PATH:
SETPOINTS > S4 CONTROLS > W1(W2) BREAKER FAIL
BF FUNCTION
Range: Disabled, Alarm, Latched Alarm
Default: Disabled
For details see Common setpoints
.
BF CURRENT
Range: 0.05 to 20.00 x CT in steps of 0.01 x CT
Default: 1.00 x CT
This setting selects the current level to be monitored by the BF logic after the
programmed time delays.
BF EXT INITIATE
Range: Off, Contact Input 1 to 10, Virtual Input 1 to 32, Remote Input 1 to 32, Logic
Element 1 to 16
Default: Off
This setting selects the external initiate signal to launch the Breaker Failure function.
BF TIME DELAY 1
Range: 0.03 to 1.00 s in steps of 0.01 s
Default: 0.1 s
This timer starts when breaker trip command is issued from any of the protection
elements.
BF TIME DELAY 2
Range: 0.00 to 1.00 s in steps of 0.01 s
Default: 0.00 s
This timer does not start before a trip condition is recognized, BF TIMER DELAY 1 has
expired, and at least one of the phase currents is above the BF CURRENT setpoint.
OUTPUT RELAY X
For details see Common setpoints
.
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