The Power Disturbance Signal Technique Research In Fault Detection Of Distribution System

These years, with the increasing power demand of the society and high requirements of the power supply reliability, fault detection issue in distribution system is significantly attracting scholars’ attentions. Utilities devote to strengthen the power system reliability to reach the optimal operation state by online condition monitoring or offline data analysis techniques. Based on the current detection issues which cannot be accurately tackled in the distribution system, we propose a novel technique called power disturbance signal detection to solve issues like anti-islanding detection in the distributed system or micro-grid system and open conductor detection in the distribution system. This detection technique has several advantages such as simple operation principles, accurate detection results and modest economic cost. This paper mainly explains two parts of applications with the technique in the distribution system.The first part describes anti-islanding detection with power disturbance signal detection technique in the distributed micro-grid system, when the main grid suffers some faults while distributed generators connected with the main grid cannot detect the abnormal state, the situation of DG is called “islanding system”. The islanding system with long time lasting will result in voltage and frequency disturbance, which cause interruption of power supply and lifetime degeneration of distributed generators. The second part is the single wire earth return system open fault detection with power disturbance signal detection technique, in some power supply region with long distance and low load capacity, single wire earth return system is adopted to save infrastructure costs. However, the regular detection methods to detect open conductor in such a long power line and locate the fault point usually take a plenty of time and energy. With two-way communication system, utilities can detect immediately and locate the fault accurately.Power disturbance signal is produced by zero-crossing distortion technique, the principle of zero-crossing distortion technique is as follows, to control power electronic device such as thyristor to create an instant short-circuit to the ground in upstream substation side, the generated disturbance signal is propagated to the downstream customer side with the power line carrier and the signal is defined as detection signal to recognize the system features, for example, if the system is at the state of fault or not. Besides in this paper, the methodology of signal generation, signal propagation, signal attenuation and signal interference, etc. are all illustrated, the system and related device parameters are all formulated. The paper also theoretically analyzed the causes of interference signal and proposed an improved anti-islanding detection scheme to deal with the issues remaining in existing zero-crossing distortion based anti-islanding protection approach. Simulation and field tests have verified the effectiveness of this technique in the application of distribution system.