GE L90 Instruction Manual page 287

CHAPTER 5: SETTINGS
Figure 5-41: Supported configurations of parallel lines in three-terminal applications
The
FAULT REP 1 REM1-TAP Z1 MAG
enter positive sequence section impedances (in secondary ohms) for the line segment from remote terminal 1 to the tap
point. The length of the line section from remote terminal 1 to the tap point is entered in the
setting.
The
FAULT REP 1 REM2-TAP Z1 MAG
above, but for the line segment from remote terminal 2 to the tap point.
The
FAULT REPORT 1 VT SUBSTITUTION
VTs are used, and the relay is supplied with the neutral (3V0) voltage, this setting is set to "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. See the
the delta and neutral voltages under the source indicated as input for the fault report. Also, the relay checks if the auxiliary
signal 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: V0 = –Z0 × I0. In order to enable this mode of operation, the
FAULT REPORT 1 VT SUBSTITUTION
The
FAULT REP 1 SYSTEM Z0 MAG
value is "I0". The magnitude is to be entered 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 is trusted accordingly. Keep in mind that grounding points in the vicinity of the installation impact the system
zero-sequence impedance (grounded loads, reactors, zig-zag transformers, shunt capacitor banks, and so on).
For proper operation of the multi-ended fault locator, the nominal primary voltage is expected to appear identical
at all line terminals as seen from the nominal secondary voltage, VT ratio, and VT connection settings of the first
87L source.
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
and
FAULT REP 1 REM1-TAP Z1 ANG
,
FAULT REP 1 REM2-TAP Z1 ANG
setting is set to "None" if the relay is fed from wye-connected VTs. If delta-connected
ACTUAL VALUES  RECORDS  FAULT REPORTS
setting is set to "I0".
and
FAULT REP 1 SYSTEM Z0 ANGLE
settings are used for three-terminal applications to
, and
FAULT REP 1 REM2-TAP LENGTH
menu for details. It is required to configure
settings are used only when the
PRODUCT SETUP
FAULT REP 1 REM1-TAP LENGTH
settings are used as
setting
VT SUBSTITUTION
5-101
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