GE L90 Instruction Manual page 190

5.5 GROUPED ELEMENTS
• 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 middle
and inner characteristics. The first step is similar to the power swing blocking sequence. After timer
times out, Latch 1 is set as long as the impedance stays within the outer characteristic.
PICKUP DELAY 1
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
2 is set as 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 characteristic and stays there for a period of time
defined as
POWER SWING PICKUP DELAY 3
the element is now ready to trip.
If the "Early" trip mode is selected, the
by the
POWER SWING SEAL-IN DELAY
leaves the inner characteristic, then times out the
ready to trip. The trip operand is 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 the
POWER SWING PICKUP DELAY 2
) and tripping (
SWING BLOCK
tacts in order to make this element fully operational.
The element can be set to use either lens (mho) or rectangular (quad) characteristics as illustrated below. When set to
"Mho", the element applies the right and left blinders as well. If the blinders are not required, their settings should be set
high enough to effectively disable the blinders.
5
Figure 5–56: POWER SWING DETECT MHO OPERATING CHARACTERISTICS
5-100
, Latch 2 is set as long as the impedance stays inside the outer characteristic;
POWER SWING TRIP
. If the "Delayed" trip mode is selected, the element waits until the impedance locus
POWER SWING PICKUP DELAY 2
timer is bypassed. It is up to the user to integrate the blocking (
) FlexLogic™ operands with other protection functions and output con-
POWER SWING TRIP
X
L90 Line Differential Relay
POWER SWING PICKUP DELAY 2
operand is set immediately and sealed-in for the interval set
and sets Latch 4; the element is now
5 SETTINGS
POWER SWING
, Latch
POWER
R
GE Multilin