GE UR Series Instruction Manual page 157

5 SETTINGS 5.5 GROUPED ELEMENTS
The Power Swing Detect element provides both power swing blocking and out-of-step tripping functions. The element mea-
sures the positive-sequence apparent impedance and traces its locus with respect to either two or three user-selectable
operating characteristic boundaries as per user choice. Upon detecting appropriate timing relations, the blocking and/or
tripping indication is given through FlexLogic™ operands. The POWER SWING OPERATING CHARACTERISTICS and
POWER SWING LOGIC figures should be viewed along with the following discussion to develop an understanding of the
operation of the element.
a) POWER SWING BLOCKING
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 characteristic (as indicated by set-
ting of the POWER SWING OUTER FlexLogic™ operand) but stays outside the middle characteristic (as indicated by set-
ting of the POWER SWING MIDDLE FlexLogic™ operand) for an interval longer than the
POWER SWING PICKUP DELAY 1
power swing blocking signal (POWER SWING BLOCK FlexLogic™ operand) is established and sealed-in. The blocking
signal resets when the locus leaves the outer characteristic, but not sooner than after time.
POWER SWING RESET DELAY 1
Two-step operation:
If the 2-step mode is selected, the sequence is identical, but it is the outer and inner characteristics that are used to time the
power swing locus.
b) OUT-OF-STEP TRIPPING
Three-step operation:
The out-of-step trip sequence identifies unstable power swings by determining if the impedance locus spends a finite time
between the outer and middle characteristics and then a finite time between the middle and inner characteristics.
5
The first step is similar to the power swing blocking sequence. After timer times out, Latch 1
POWER SWING PICKUP DELAY 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 character-
istic but stays outside the inner characteristic for a period of time defined as , Latch 2 is set as
POWER SWING PICKUP DELAY 2
long as the impedance stays inside the outer characteristic.
If afterwards, at any time (given the impedance stays within the outer characteristic), the locus enters the inner characteris-
tic and stays there for a period of time defined as , Latch 2 is set as long as the impedance
POWER SWING PICKUP DELAY 3
stays inside the outer characteristic - the element is now ready to trip.
If the "Early" trip mode is selected, operand POWER SWING TRIP is set immediately and is sealed-in for the interval estab-
lished by setting .
POWER SWING SEAL-IN DELAY
If the "Delayed" trip mode is selected, the element waits until the impedance locus leaves the inner characteristic, then
times out the delay, and sets Latch 4 - the element is now ready to trip. The trip operand will
POWER SWING PICKUP DELAY 2
be set later, when the impedance locus leaves the outer characteristic.
Two-step operation:
The 2-step mode of operation is similar to the 3-step mode with two exceptions. First, the initial stage monitors the time
spent by the impedance locus between the outer and inner characteristics. Second, the stage involving timer POWER
SWING PICKUP DELAY 2 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 output contacts in order to make this element fully operational.
GE Power Management L90 Line Differential Relay 5-73