GE N60 Instruction Manual page 353

CHAPTER 5: SETTINGS
The power swing detect element provides both power swing blocking and out-of-step tripping functions. The element
measures the positive-sequence apparent impedance and traces its locus with respect to either two or three user-
selectable operating characteristic boundaries. Upon detecting appropriate timing relations, the blocking and/or tripping
indications are given through FlexLogic operands. The element incorporates an adaptive disturbance detector. This
function does not trigger on power swings, but is capable of detecting faster disturbances—faults in particular—that can
occur during power swings. Operation of this dedicated disturbance detector is signaled via the
operand.
The power swing detect element asserts two operands intended for blocking selected protection elements on power
swings: is a traditional signal that is safely asserted for the entire duration of the power swing, and
POWER SWING BLOCK
is established in the same way, but resets when an extra disturbance is detected during the power
POWER SWING UN/BLOCK
swing. The
POWER SWING UN/BLOCK
respond to faults during power swing conditions.
Different protection elements respond differently to power swings. If tripping is required for faults during power swing
conditions, some elements can be blocked permanently (using the
blocked and dynamically unblocked upon fault detection (using the
View the operating characteristic and logic figures along with the following discussion to understand the operation of the
element.
The power swing detect element operates in three-step or two-step mode, as follows:
• 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
, the power swing blocking signal
PICKUP DELAY 1
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 to the three-step operation, 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
times out, latch 1 is set as long as the impedance stays within the outer characteristic.
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
POWER SWING PICKUP DELAY 3
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 for the
now ready to trip. The trip operand is set later, when the impedance locus leaves the outer characteristic.
N60 NETWORK STABILITY AND SYNCHROPHASOR MEASUREMENT SYSTEM – INSTRUCTION MANUAL
POWER SWING TRIP

MODE: Delayed
POWER SWING BLK:

Off
POWER SWING

TARGET: Self-reset
POWER SWING

EVENTS: Disabled
operand can be used for blocking selected protection elements if the intent is to
FlexLogic operand) but stays outside the middle
POWER SWING OUTER
FlexLogic operand) for an interval longer than
POWER SWING MIDDLE
(POWER SWING BLOCK
, 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 TRIP
. If the "Delayed" trip mode is selected, the element waits until the impedance locus
POWER SWING PICKUP DELAY 2
Range: Early, Delayed
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
operand), and others can be
POWER SWING BLOCK
operand).
POWER SWING UN/BLOCK
FlexLogic operand) is established and sealed-in.
POWER SWING PICKUP DELAY 2
and sets latch 4; the element is
GROUPED ELEMENTS
POWER SWING 50DD
POWER SWING
POWER SWING RESET
POWER
,
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