Study and Realizing of Method of AC Locating Fault in Distribution System

The idea of AC locating fault method in distribution system is that inject an AC signal into the fault phase after a single line to ground fault happened and then diagnose the fault along the transmission line with the handled AC signal detector utilizing dichotomy method until the fault is determined. The frequency of the injected AC signal used in this study is 60 Hz. Compared with the injected S signal technique, this method is called low frequency AC signal injection method. In this paper, the hardware of the signal source and the software design are introduced. The SCM managing pulse is used in the control section of the hardware, and the application of PWM control technique in this hardware is discussed in this reference; as the software design, the PWM signal is generated by coding based on the relation between the injected signal and PWM waveforms. The high frequency PWM signal excited a couple of breakers in the inversion source and then the output terminal will get high stable injected signals by filtering and generate AC signal with invariable frequency and adjustable voltage, based on which the signal detector could detect the required signal easily. The proposed signal source device reduces the difficulty of high impedance to ground detecting and improves the accuracy and reliability of locating fault. This technique, which allows the ground detecting and is convenient for engineers´ operation, reduces the locating fault time, improves its efficiency and is proved by simulation and analysis on its validity.