Research on automatic location of single-phase leakage fault zone in coal mine power network

Abstract

The necessity of automatic single-phase leakage fault zone location is analyzed in this paper from two aspects, namely, the need for leakage detection and the value of leakage fault zone location. Three single-phase leakage fault mechanism models' principles are introduced, namely, fault steady-state process sequence network model, fault transient state process sequence network model and transient steady-state integrated sequence network model, and the problems are pointed out as follows. The steady-state characteristics are applicable to systems with ungrounded neutral points, and in the system with grounded arc suppression coil, there are blind spots in the steady-state characteristics. The inconsistency of transient steady-state modeling methods leads to inconsistent subsequent fault signals. For research on single-phase leakage fault mechanism models, it is suggested to integrate the transient and steady-state processes for accurate modeling and explore the data-driven fault process research. The principle of the fault characteristic signal processing method based on wavelet (packet) and other algorithms is introduced, and the problems are pointed out as follows. The existing fault characteristic law studies mainly focus on line selection and distance measurement. There are few research on the signal characteristics and its distribution of the upstream and downstream zones of the fault. The obtained fault characteristic law is mainly for permanent faults, and there are few researches on arc faults. The extracted signal characteristics are aliased. For the study of fault characteristic law, it is suggested to study the mechanism and characteristic law of arc faults and study the practical and effective signal analysis and characteristic extraction algorithms. The principle of single-phase leakage fault zone location method based on steady state and transient state quantities is introduced, and the problems are pointed out as follows. The steady-state characteristics are easily affected by the compensation effect of the arc suppression coil, which leads to inaccurate zone location. The transient characteristics are fast decaying and unstable, and cannot be used to locate faults such as voltage zero crossing and high resistance grounding. The single-phase leakage fault characteristics are weak and easily affected by unstable fault arcs and random factors. For research on automatic single-phase leakage fault zone location methods, it is suggested to apply pattern identification, artificial intelligence, digital twin and other technologies. These technologies are used to explore fault zone location methods for small-current grounding systems applicable to different neutral point operation modes, and eliminate the influence of arc suppression coils on fault identification. For weak and complex fault signals, special high-precision sensors are studied to achieve accurate acquisition of signal detection.

Keywords

• coal mine power network; single-phase leakage fault; zone location; transient zero sequence current; fault line selection