GE D90 Plus Instruction Manual page 187

CHAPTER 7: PROTECTION
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Function
Range: Enabled, Disabled
Default: Disabled
This setting enables and disables the power swing detection element. The setting
applies to both power swing blocking and out-of-step tripping functions.
Source
Range: LINE (SRC 1), BKR 1 (SRC 2), BKR 2 (SRC 3)
Default: LINE (SRC 1)
This setting selects the signal source for both blocking and tripping functions.
Shape
Range: Mho, Quad
Default: Mho
This setting selects the shapes (either mho or quadrilateral) of the outer, middle and,
inner characteristics of the power swing detect element. The operating principle is not
affected. The mho characteristics use the left and right blinders.
Mode
Range: Two Step, Three Step
Default: Two Step
This setting selects the two-step or three-step operating mode and applies it to both
power swing blocking and out-of-step tripping functions. The three-step mode applies if
there is enough space between the maximum load impedances and distance
characteristics of the relay that all three (outer, middle, and inner) characteristics can be
placed between the load and the distance characteristics. Whether the spans between
the outer and middle as well as the middle and inner characteristics are sufficient
should be determined by analysis of the fastest power swings expected in correlation
with settings of the power swing timers.
The two-step mode uses only the outer and inner characteristics for both blocking and
tripping functions. This leaves more space in heavily loaded systems to place two power
swing characteristics between the distance characteristics and the maximum load, but
allows for only one determination of the impedance trajectory.
Supervision
Range: 0.050 to 30.000 pu in steps of 0.001
Default: 0.600
A common overcurrent pickup level supervises all three power swing characteristics. The
supervision responds to the positive-sequence current.
Forward Reach
Range: 0.10 to 500.00 ohms in steps of 0.01
Default: 2.50 ohms
This setting specifies the forward reach of all three mho characteristics and the inner
quadrilateral characteristic. For a simple system consisting of a line and two equivalent
sources, this reach should be higher than the sum of the line and remote source
positive-sequence impedances. Detailed transient stability studies may be needed for
complex systems in order to determine this setting. The angle of this reach impedance is
specified by the
Forward RCA
Quadrilateral Forward Middle
Range: 0.10 to 500.00 ohms in steps of 0.01
Default: 60.00 ohms
This setting specifies the forward reach of the middle quadrilateral characteristic. The
angle of this reach impedance is specified by the
used if the shape setting is "Mho".
GROUPED PROTECTION ELEMENTS
setting.
Forward RCA setting. The setting is not
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