A Faulty Line Selection Study And The Corresponding Equipment Of Non-effectively Grounded System Single-phase-to-ground Fault Based On Integrative Methods

Due to its irreplaceable superiority,non-effectively grounded system has been widely used in our country and other distribution networks in many countries. However, for single-phase-to-ground fault,the faulty line selection has been one of the major technical problems of the relay protection in power system because of the weak fault current, instable arc light and other reasons. Therefore,further study of small current grounding line selection and development of fault-line selection instrument with high accuracy,has an important theoretical and practical value.Based on the analysis of faulty characteristics when single-phase-to-ground fault occurs in small current grounding system,this paper looks over a variety of existing line selection methods,and raises a information integration and continuous line selection strategy aiming at the deficiency of single line selection principle. In accordance with the different kind of neutral grounding, this paper selects multiple complementary steady-state and transient line selection methods for the integrative methods, and establishes a small current grounding system simulation model based on Matlab and makes a large number of simulation, and subsequently conducts a in-depth analysis and comparison of the methods selected in the integrative methods.For the benefit of information fusion, this paper defines a variety of faulty measurement function, gives the relative faulty measurement function and determines the detailed structure of faulty measurement function. This paper uses wavelet decomposition and reconstruction algorithm, making the detail coefficient of the transient fault information detail band additive, and takes full advantage of the size and polarity information of all details signal at different sampling points to construct the faulty measurement function, improving traditional methods which just applies only a single polarity information.On this basis,this paper puts forward a continuous line selection program using the fuzzy theory to fuse steady-state and transient fault information. Aiming at the deficiency of information fusion with fuzzy theory, this paper proposes a continuous selection line program using evidence theory to fuse steady-state and transient fault information. The implementation of the two programs is detailed.According to the established line selection program, this paper develops a line selection equipment,and introduces the structure of hardware devices and software processes. The hardware devise is based on a 32-bit high-performance ARM chip STM32F103VET6, and pays attention to the design of weak signal processing capability, basically satisfying the data processing and signal acquisition requirements. Applying modular design, the software processes are of clear structure and easy to be tested.