GE N60 Instruction Manual page 288

GROUPED ELEMENTS
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 characteristic (indicated by the
characteristic (indicated by the
1, the power swing blocking signal
PICKUP DELAY
The blocking signal resets when the locus leaves the outer characteristic, but not sooner than the
time.
DELAY 1
• Two-step operation — If the two-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.
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
impedance 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
SWING PICKUP DELAY 1
If afterwards, at any time (given the impedance stays within the outer characteristic), the locus enters the middle
characteristic but stays outside the inner characteristic for a period of time defined as
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
characteristic; 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
5
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
contacts in order to make this element fully operational.
The element can be set to use either lens (mho) or rectangular (quadrilateral) characteristics, as shown in the figure. When
set to "Mho", the element applies the right and left blinders as well. If the blinders are not required, set their settings high
enough to effectively disable the blinders.
5-172
POWER SWING OUTER
POWER SWING MIDDLE
times out, latch 1 is set as long as the impedance stays within the outer characteristic.
POWER SWING PICKUP DELAY 3
POWER SWING TRIP
. If the "Delayed" trip mode is selected, the element waits until the impedance locus
POWER SWING PICKUP DELAY 2
BLOCK) and tripping (POWER SWING
Figure 5-78: Power swing detect mho operating characteristics
N60 NETWORK STABILITY AND SYNCHROPHASOR MEASUREMENT SYSTEM – INSTRUCTION MANUAL
FlexLogic operand) but stays outside the middle
FlexLogic operand) for an interval longer than
(POWER SWING BLOCK FlexLogic operand) is established and sealed-in.
, latch 2 is set as long as the impedance stays inside the outer
operand is set immediately and sealed-in for the interval set
POWER SWING PICKUP DELAY 2
timer is bypassed. It is up to the user to integrate the blocking
TRIP) FlexLogic operands with other protection functions and output
X
CHAPTER 5: SETTINGS
POWER SWING
POWER SWING RESET
POWER SWING PICKUP DELAY 2
and sets Latch 4; the element is now
R
POWER
,