Research On Advanced Methods Of Single Phase Grounding Protection And Their Implementing With Information Fusion In Distribution Networks

Neutral ineffectively earthed systems include neutral unearthed, neutral earthed by high resistance and neutral resonance earthed systems. They are widely employed in medial and low voltage distribution networks of China. They are benefit to improve the reliability of power system. However when a single line-to-earth fault occurs, they are rather difficult to identify the fault feeder because the fault currents are much too small, especially under disturbance and detecting error. The problem of how to detect and isolate fault feeder correctly and reliably, and look for a protection method with high precision is always an important research task. Especially as the development of distribution automation (DA), the traditional fault line selecting methods are not easy to apply in feeder protection and install on FTU, so it is necessary to develop new protection scheme to meet the need of distribution automation.This thesis deals with these problems, aims to find the deficiency of existing method, to look for new selection method and research information fusion of many selection methods. Firstly, as a basis, the research actualities of fault detecting in neutral ineffectively earthed networks are discussed in this thesis, and the existing methods are analyzed systemically, the strongpoint and shortcoming of them are pointed out. Secondly, on the basis of them, grounding resistance protection method and phase current sampling value differential protection method are developed. They are simulated by EMIT software, the result of simulation show that they have high sensitivity and robustness. Because a single fault protection scheme has poor precision in ground fault detection, information fusion technology is discussed and many selection methods are fused. Thirdly, information fusion protection programs are written in C language on the basis of DSP chip, the function of protection is realized. Finally, tests have been done on a dynamic power system model in the laboratory and the program is debugged. Results show that the information fusion protection method developed in this thesis has high reliability and robustness. The problem of fault line selection in neutral ineffectively earthed system is solved with better effect.