Study On The New Technology Of Protection And Controlling For Distribution Networks

In this dissertation, new technology of protection and control of distribution networks is discussed. The dissertation is focused on the related protection and control techniques to realize distribution automation. Fault detection and fault isolation is the topic, so as to its realization in the intelligent electric devices.Based on the experiences of other countries, an integrate distribution automation system design and its fulfillment process are proposed to fit the status of distribution networks in china. The system structure and control mode of distribution automation system are mainly concerned. To analyze the performance of distribution networks, a digital simulation program based on EMTP/ATP is designed. Delicate models are setup for this program, such as lines, circuit transformers, loads, and Peterson Coil. And protection systems are embedded in it. All these measures can enhance the efficiency and flexibility of the simulation. It can also be a helpful simulation tool to validate the effectiveness of fault detection and fault isolation methods.An adaptive overcurrent relay based on the principle of phase-to-phase differential current (PDC) is presented. According to its inputs, it can be specified into two kinds. One is adaptive relay based on current inputs, which can recognize the fault type of distribution line. The other is adaptive relay based on both current and voltage inputs, which can recognize both fault type and operation mode of distribution networks. Then, some new ground-fault detection methods based on correlation analysis and evidence theory are proposed. Considered the fault property and the correlation of the waveform of different lines, the accuracy of ground-fault detection can be improved through data processing. A protection and control system based on multi-agent system (MAS) is proposed. The characteristics, structure, model and decision-making process of this system is elaborated. Through the coordination among many distributed protection agents, the process of relay tripping and fault detection can be accelerated. The control operation can be more effectively and quickly. At last, a novel intelligent terminal device integrated with protection, supervision and control functions for ring main units, named RMU, is researched and developed. Its hardware structure is based on multi-DSP system. And it can complete many functions, such as fault detection, fault isolation, data processing, power quality supervision, harmonic analysis, et al. All of the new technology of protection and control for distribution networks researched in this dissertation are put into use in this device.