GE L30, Инструкция по эксплуатации

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CHAPTER 10: THEORY OF OPERATION FAULT LOCATOR
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 10-21
10
Figure 10-9: Equivalent system for fault location
The following equations hold true for this equivalent system.
Eq. 10-37
where
m = sought pu distance to fault
Z = positive sequence impedance of the line
I
F
= fault current flowing through the fault point
The fault network during a fault can be decomposed into a pre-fault and a pure-fault network. Therefore, the fault current
I
F
is calculated as follows by using the current division rule in the pure-fault network.
Eq. 10-38
where
d is the current distribution factor, which is a complex value
Substituting the second equation into the first equation and multiplying both sides by the complex conjugate of IAF,
Eq. 10-39
where
* denotes complex conjugate
Assuming the system is homogeneous, d is then a real number. The fault resistance does not have any imaginary part. The
preceding equation solved for the unknown m yields the following fault location algorithm:
Eq. 10-40
where
Im( ) stands for the imaginary part of a complex number
Depending on the fault type, appropriate voltage and current signals are selected from the phase quantities before
applying the preceding equation (the superscripts denote phases, the subscripts denote stations).
For AG faults:
Eq. 10-41