GE T60 Instruction Manual page 518

GROUPED ELEMENTS
Settings
— This setting is used to select the breaker failure operating mode: single or three pole.
BF1 MODE
BF1 USE AMP SUPV
5
pickup level.
— If set to "Yes," the element is sealed-in if current flowing through the breaker is above the supervision
BF1 USE SEAL-IN
pickup level.
BF1 3-POLE INITIATE
BF1 RETRIP PICKUP DELAY
possible spurious contact input activation duration due to transients or temporary DC grounds, taking into account the
contact input de-bounce time to avoid re-trip operation for such transients.
BF1 PH AMP SUPV PICKUP
setting detects the lowest expected fault current on the protected breaker. It can be set as low as necessary (lower than
breaker resistor current or lower than load current)—high-set and low-set current supervision guarantee correct operation.
BF1 N AMP SUPV PICKUP
setting detects the lowest expected fault current on the protected breaker. Neutral current supervision is used only in the
three phase scheme to provide increased sensitivity. This setting is valid only for three-pole tripping schemes.
— If set to "Yes," the early path is operational.
BF1 USE TIMER 1
BF1 TIMER 1 PICKUP DELAY
the time the initial trip signal is applied to the breaker trip circuit, plus a safety margin.
— If set to "Yes," the main path is operational.
BF1 USE TIMER 2
BF1 TIMER 2 PICKUP DELAY
margin was historically intended to allow for measuring and timing errors in the breaker failure scheme equipment. In
microprocessor relays this time is not significant. In T60 relays, which use a Fourier transform, the calculated current
magnitude ramps-down to zero one power frequency cycle after the current is interrupted, and this lag needs to be
included in the overall margin duration, as it occurs after current interruption. The Breaker Failure Main Path Sequence
figure that follows shows a margin of two cycles; this interval is considered the minimum appropriate for most
applications.
Note that in bulk oil circuit breakers, the interrupting time for currents less than 25% of the interrupting rating can be
significantly longer than the normal interrupting time.
— If set to "Yes," the Slow Path is operational.
BF1 USE TIMER 3
5-300
Figure 5-170: Breaker failure overcurrent supervision reset time
— If set to "Yes," the element is initiated if current flowing through the breaker is above the supervision
— This setting selects the FlexLogic operand that initiates three-pole tripping of the breaker.
— This setting specifies a pickup delay for the re-trip command. Set this delay longer than the
— This setting is used to set the phase current initiation and seal-in supervision level. Generally this
— This setting is used to set the neutral current initiate and seal-in supervision level. Generally this
— Timer 1 is set to the shortest time required for breaker auxiliary contact Status-1 to open, from
— Timer 2 is set to the expected opening time of the breaker, plus a safety margin. This safety
T60 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS