GE T60 Instruction Manual page 463

CHAPTER 5: SETTINGS
Settings
— This setting is used to select the breaker failure operating mode: single or three pole.
BF1 MODE
— If set to "Yes," the element is initiated if current flowing through the breaker is above the supervision
BF1 USE AMP SUPV
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.
— This setting selects the FlexLogic operand that initiates three-pole tripping of the breaker.
BF1 3-POLE INITIATE
— This setting is used to set the phase current initiation and seal-in supervision level. Generally this
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.
— This setting is used to set the neutral current initiate and seal-in supervision level. Generally this
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
— Timer 1 is set to the shortest time required for breaker auxiliary contact Status-1 to open, from
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
— Timer 2 is set to the expected opening time of the breaker, plus a safety margin. This safety
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
— Timer 3 is set to the same interval as timer 2, plus an increased safety margin. Because this
BF1 TIMER 3 PICKUP DELAY
path is intended to operate only for low level faults, the delay can be in the order of 300 to 500 ms.
φ
— This setting selects the FlexLogic operand that represents the protected breaker early-type auxiliary
BF1 BKR POS1 A/3P
switch contact (52/a). When using the single-pole breaker failure scheme, this operand represents the protected breaker
early-type auxiliary switch contact on pole A. This is normally a non-multiplied form-A contact. The contact can even be
adjusted to have the shortest possible operating time.
φ
— This setting selects the FlexLogic operand that represents the breaker normal-type auxiliary switch
BF1 BKR POS2 A/3P
contact (52/a). When using the single-pole breaker failure scheme, this operand represents the protected breaker auxiliary
switch contact on pole A. This can be a multiplied contact.
— This setting is used to select the FlexLogic operand that represents the breaker in-service/out-of-
BF1 BREAKER TEST ON
service switch set to the out-of-service position.
— This setting sets the phase current output supervision level. Generally this setting is to detect
BF1 PH AMP HISET PICKUP
the lowest expected fault current on the protected breaker, before a breaker opening resistor is inserted.
— This setting sets the neutral current output supervision level. Generally this setting is to detect
BF1 N AMP HISET PICKUP
the lowest expected fault current on the protected breaker, before a breaker opening resistor is inserted. Neutral current
supervision is used only in the three pole scheme to provide increased sensitivity. This setting is valid only for three-pole
breaker failure schemes.
— This setting sets the phase current output supervision level. Generally this setting is to detect
BF1 PH AMP LOSET PICKUP
the lowest expected fault current on the protected breaker, after a breaker opening resistor is inserted (approximately 90%
of the resistor current).
T60 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
GROUPED ELEMENTS
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