GE G60 UR Series, Instruction Manual

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GE Multilin G60 Generator Protection System 5-135
5 SETTINGS 5.6 GROUPED ELEMENTS
5
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 middle
and inner characteristics. The first step is similar to the power swing blocking sequence. After timer
POWER SWING
PICKUP 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
, latch
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
, 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 interval
set by the
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
POWER SWING PICKUP DELAY 2
and sets Latch 4; the element is
now 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, 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
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
output 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 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.
Figure 5–64: POWER SWING DETECT MHO OPERATING CHARACTERISTICS
OUTER
MIDDLE
INNER
REV RCA
FWD RCA
REV REACH
INNER LIMIT ANGLE
MIDDLE LIMIT ANGLE
OUTER LIMIT ANGLE
827843A2.CDR
FWD REACH
R
X