GE L90 Instruction Manual page 732

FAULT LOCATOR
10.6.2.2 Estimation of fault resistance
Once the fault is located by the multi-ended location method, the fault resistance can be estimated by the following
equation.
where
R is the fault resistance
F
V is voltage at the fault point
F
I is current flowing into the fault point
F
Depending on the fault type, appropriate fault voltage and current signals are selected from the phase quantities before
applying the equation above. The following equations describe the voltage and current quantities for the three-terminal
applications, where the subscript (X) denotes the line terminal of the faulted segment/line, (TAP) denotes the tap point the
fault section, and current flowing towards the fault from the tap point is the summation of currents of the two unfaulted
line segments.
For AG faults:
where
Z0 is the impedance of the zero-sequence impedance of the faulted segment/line
Z0M is the mutual zero sequence impedance
For BG faults:
For CG faults:
For AB/ABG faults:
For BC/BCG faults:
10
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CHAPTER 10: THEORY OF OPERATION
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
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