GE D90 Plus Instruction Manual page 521

CHAPTER 10: DIGITAL FAULT RECORDER
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Line Length Units
Range: km, miles
Default: km
This setting selects the units used for fault location calculations.
Line Length
Range: 0.0 to 2000.0 in steps of 0.1
Default: 100.0
This setting specifies the length of the transmission line or feeder in the defined line
length units.
Fault Report VT Substitution
Range: None, I0, V0
Default: None
Program this setting to "None" if the D90
connected VTs are used, and the D90
"V0." The method is still exact, as the fault locator combines the line-to-line voltage
measurements with the neutral voltage measurement to re-create the line-to-ground
voltages. It required to configure the delta and neutral voltages under the source
indicated as input for the fault report. Also, the D90
configured is marked as "Vn" by the user (under VT setup) and inhibits the fault location if
the auxiliary signal is labeled differently.
If the broken-delta neutral voltage is not available to the relay, an approximation is
possible by assuming the missing zero-sequence voltage to be an inverted voltage drop
produced by the zero-sequence current and the user-specified equivalent zero-
sequence system impedance behind the relay: V_0 = –Z_0 × I_0. In order to enable this
mode of operation, set the value to "I0".
Fault Report System Z0 Magnitude
Range: 0.01 to 650.00 ohms in steps of 0.01
Default: 2.00 ohms
This setting is used when the
magnitude in secondary ohms. This impedance is an average system equivalent behind
the relay. It can be calculated as zero-sequence Thevenin impedance at the local bus
with the protected line/feeder disconnected. The method is accurate only if this setting
matches perfectly the actual system impedance during the fault. If the system exhibits
too much variability, this approach is questionable and the fault location results for
single-line-to-ground faults are trusted accordingly. Keep in mind that grounding points
in vicinity of the installation impact the system zero-sequence impedance (grounded
loads, reactors, zig-zag transformers, shunt capacitor banks, and so on).
Fault Report System Z0 Angle
Range: 25 to 90° in steps of 1
Default: 75°
This setting is used when the
corresponding angle for the
The figure shows the fault locator logic.
Plus
is fed from wye-connected VTs. If delta-
Plus
is supplied with the neutral (3V0) voltage, set to
Plus
Fault Report VT Substitution
Fault Report VT Substitution
Fault Report System Z0 Magnitude
FAULT REPORT
checks if the auxiliary signal
value is "I0". Enter the
value is "I0" and represents the
setting.
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