A New Fault-Location Algorithm for Extra-High-Voltage Mixed Lines Based on Phase Characteristics of the Hyperbolic Tangent Function

A new fault-location algorithm for extra-high-voltage mixed lines based on phase characteristics of the hyperbolic tangent function is proposed. This paper takes overhead-cable-overhead mixed lines for example. The faulted section identification functions for overhead cable connections described by the hyperbolic tangent are developed separately when faults occur on the first overhead line, the middle cable, and the last overhead line. When a fault occurs on different sections, the faulted section identification functions appear as obviously different phase characteristics according to the phase characteristics of the hyperbolic tangent function. Thus, the faulted section can be identified. The fault location can be therefore accurately determined with the voltage and current positive-sequence fault components on both ends of the faulted section. Simulations and calculations with PSCAD and MATLAB show that the fault-location algorithm is correct and accurate.

I. Introduction

Underground cables have been widely implemented due to reliability and environmental concerns [1]. Basically, the location methods for cables are divided into the offline [2], [3] and online methods [4], [5]. Reference [5] proposes a fault-location method based on voltage and current phasors measured from a single terminal. Fault types, such as core-sheath-ground fault, core-ground fault, and core-sheath fault can be determined prior to the calculation of fault distance. A traveling-wave-based fault-location scheme for multiend aged cables is proposed in [6]. The faulted section is identified according to the first detected transient wave and then the exact fault location is estimated.