GE Multilin L60 Line Phase Comparison System 5-1675 SETTINGS 5.5 GROUPED ELEMENTS5The operating characteristic and logic figures should be viewed along with the following discussion to develop an under-standing of the operation of the element.The power swing detect element operates in three-step or two-step mode:• Three-step operation: The power swing blocking sequence essentially times the passage of the locus of the positive-sequence impedance between the outer and the middle characteristic boundaries. If the locus enters the outer charac-teristic (indicated by the POWER SWING OUTER FlexLogic operand) but stays outside the middle characteristic (indi-cated by the POWER SWING MIDDLE FlexLogic operand) for an interval longer than POWER SWING PICKUP DELAY 1, thepower swing blocking signal ( POWER SWING BLOCK FlexLogic operand) is established and sealed-in. The blocking sig-nal resets when the locus leaves the outer characteristic, but not sooner than the POWER SWING RESET DELAY 1 time.• Two-step operation: If the two-step mode is selected, the sequence is identical, but it is the outer and inner character-istics that are used to time the power swing locus.The out-of-step tripping feature operates as follows for three-step and two-step power swing detection modes:• Three-step operation: The out-of-step trip sequence identifies unstable power swings by determining if the imped-ance locus spends a finite time between the outer and middle characteristics and then a finite time between the middleand inner characteristics. The first step is similar to the power swing blocking sequence. After timer POWER SWINGPICKUP DELAY 1 times out, latch 1 is set as long as the impedance stays within the outer characteristic.If afterwards, at any time (given the impedance stays within the outer characteristic), the locus enters the middle char-acteristic but stays outside the inner characteristic for a period of time defined as POWER SWING PICKUP DELAY 2, latch2 is set as long as the impedance stays inside the outer characteristic. If afterwards, at any time (given the impedancestays within the outer characteristic), the locus enters the inner characteristic and stays there for a period of timedefined as POWER SWING PICKUP DELAY 3, latch 2 is set as long as the impedance stays inside the outer characteristic;the element is now ready to trip.If the "Early" trip mode is selected, the POWER SWING TRIP operand is set immediately and sealed-in for the intervalset by the POWER SWING SEAL-IN DELAY. If the "Delayed" trip mode is selected, the element waits until the impedancelocus leaves the inner characteristic, then times out the POWER SWING PICKUP DELAY 2 and sets Latch 4; the element isnow ready to trip. The trip operand is set later, when the impedance locus leaves the outer characteristic.• Two-step operation: The two-step mode of operation is similar to the three-step mode with two exceptions. First, theinitial stage monitors the time spent by the impedance locus between the outer and inner characteristics. Second, thestage involving the POWER SWING PICKUP DELAY 2 timer is bypassed. It is up to the user to integrate the blocking( POWER SWING BLOCK ) and tripping (POWER SWING TRIP) FlexLogic operands with other protection functions and out-put contacts in order to make this element fully operational.The element can be set to use either lens (mho) or rectangular (quadrilateral) characteristics as illustrated below. When setto “Mho”, the element applies the right and left blinders as well. If the blinders are not required, their settings should be sethigh enough to effectively disable the blinders.
