GE UR Series Instruction Manual page 161

5 SETTINGS 5.5 GROUPED ELEMENTS
The inner characteristic is also used by the power swing blocking function in the 2-step mode. Therefore, this angle must
be set large enough so that the characteristics of the distance elements are safely enclosed by the inner 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 pro-
duce out-of-step tripping in a secure manner. The timers should be set in consideration to the power swing detect charac-
teristics, 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 characteristics (2-step
operating mode), or between the outer and middle characteristics (3-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. Detection of a condition requiring a Block output
sets Latch 1 after time. When the impedance locus leaves the outer characteristic, timer
PICKUP DELAY 1 POWER SWING
is started. When the timer times-out the latch is reset.
RESET DELAY 1
This setting should be selected to give extra security for the power swing blocking action.
POWER SWING PICKUP DELAY 2:
This setting controls the out-of-step tripping function in the 3-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.
5
POWER SWING PICKUP DELAY 3:
This setting controls the out-of-step tripping function only. This timer defines the interval the impedance locus must spend
within the inner characteristic before the last step of the out-of-step tripping sequence is completed and the element is
armed to trip. The actual moment of tripping is controlled by the setting.
TRIP MODE
This time delay is provided for extra security before the out-of-step trip action is executed.
POWER SWING PICKUP DELAY 4:
This setting controls the out-of-step tripping function in the 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 gets
armed for the Delayed trip. The delayed trip will take place when the impedance leaves the outer characteristic.
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 character-
istic. 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.
GE Power Management L90 Line Differential Relay 5-77