GE T60, Instruction Manual

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GE Multilin T60 Transformer Protection System 5-207
5 SETTINGS 5.6 GROUPED ELEMENTS
5
nite (the actual trip may be delayed as per the
TRIP MODE
setting). Therefore, this angle must be selected in consider-
ation to the power swing angle beyond which the system becomes unstable and cannot recover.
The inner characteristic is also used by the power swing blocking function in the two-step mode. In this case, set this
angle large enough so that the characteristics of the distance elements are safely enclosed by the inner characteristic.
This setting applies to mho shapes only.
• POWER SWING OUTER , MIDDLE , and INNER RGT BLD : These settings specify the resistive reach of the right
blinder. The blinder applies to both “Mho” and “Quad” characteristics. Set these value high if no blinder is required for
the “Mho” characteristic.
• POWER SWING OUTER , MIDDLE , and INNER LFT BLD : These settings specify the resistive reach of the left blinder.
Enter a positive value; the relay automatically uses a negative value. The blinder applies to both “Mho” and “Quad”
characteristics. Set this value high if no blinder is required for the “Mho” characteristic.
• POWER SWING PICKUP DELAY 1: All the coordinating timers are related to each other and should be set to detect
the fastest expected power swing and produce out-of-step tripping in a secure manner. The timers should be set in
consideration to the power swing detect characteristics, mode of power swing detect operation and mode of out-of-
step tripping. This timer defines the interval that the impedance locus must spend between the outer and inner charac-
teristics (two-step operating mode), or between the outer and middle characteristics (three-step operating mode)
before the power swing blocking signal is established. This time delay must be set shorter than the time required for
the impedance locus to travel between the two selected characteristics during the fastest expected power swing. This
setting is relevant for both power swing blocking and out-of-step tripping.
• POWER SWING RESET DELAY 1: This setting defines the dropout delay for the power swing blocking signal. Detec-
tion of a condition requiring a block output sets latch 1 after
PICKUP DELAY 1
time. When the impedance locus leaves
the outer characteristic, timer
POWER SWING RESET DELAY 1
is started. When the timer times-out the latch is reset. This
setting should be selected to give extra security for the power swing blocking action.
• POWER SWING PICKUP DELAY 2: Controls the out-of-step tripping function in the three-step mode only. This timer
defines the interval the impedance locus must spend between the middle and inner characteristics before the second
step of the out-of-step tripping sequence is completed. This time delay must be set shorter than the time required for
the impedance locus to travel between the two characteristics during the fastest expected power swing.
• POWER SWING PICKUP DELAY 3: Controls the out-of-step tripping function only. It defines the interval the imped-
ance locus must spend within the inner characteristic before the last step of the out-of-step tripping sequence is com-
pleted and the element is armed to trip. The actual moment of tripping is controlled by the
TRIP MODE
setting. This time
delay is provided for extra security before the out-of-step trip action is executed.
• POWER SWING PICKUP DELAY 4: Controls the out-of-step tripping function in “Delayed” trip mode only. This timer
defines the interval the impedance locus must spend outside the inner characteristic but within the outer characteristic
before the element is armed for the delayed trip. The delayed trip occurs when the impedance leaves the outer charac-
teristic. This time delay is provided for extra security and should be set considering the fastest expected power swing.
• POWER SWING SEAL-IN DELAY: The out-of-step trip FlexLogic operand (
POWER SWING TRIP
) is sealed-in for the
specified period of time. The sealing-in is crucial in the delayed trip mode, as the original trip signal is a very short
pulse occurring when the impedance locus leaves the outer characteristic after the out-of-step sequence is completed.
• POWER SWING TRIP MODE: Selection of the “Early” trip mode results in an instantaneous trip after the last step in
the out-of-step tripping sequence is completed. The early trip mode will stress the circuit breakers as the currents at
that moment are high (the electromotive forces of the two equivalent systems are approximately 180° apart). Selection
of the “Delayed” trip mode results in a trip at the moment when the impedance locus leaves the outer characteristic.
delayed trip mode will relax the operating conditions for the breakers as the currents at that moment are low. The
selection should be made considering the capability of the breakers in the system.
• POWER SWING BLK: This setting specifies the FlexLogic operand used for blocking the out-of-step function only. The
power swing blocking function is operational all the time as long as the element is enabled. The blocking signal resets
the output
POWER SWING TRIP
operand but does not stop the out-of-step tripping sequence.