| 摘要 |
Faults on power lines are detected by measuring the voltage and current at o ne end of a power line and uses these measurements, together with values of series and shunt parameters of the line, to calculate values of voltage and current at an intermediate point on the line - the so-called "reach point". At least the calculated voltage i s used to determine whether a fault lies within a particular zone on the line. The calculation utilizes a value of a derivative of said measured current with respect to time and is able to ta ke into account the sectioning of a line into discrete lengths corresponding to, for example , overhead and cable sections. To increase accuracy, the line or each discrete section of t he line is conceptually divided into subsections each having their own parameter values . In a second aspect of the invention, detection of whether a fault lies within a particul ar zone involves the measurement of first-end voltage and current both before and after the fault, the calculation of the complex impedance between an intermediate point of the li ne and a reference point, normally earth, using these measured values and values relating to line parameters and to a source impedance of the second end of the line, and the determination of the sign of the complex impedance.
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