| Reliability, economy and quality is three important aspects of power system. Single-phase ground faults are the most common faults in power system. In order to improve the reliability of power supply, most 6～35kV distribution networks in China have been running in non-effective grounded mode. The current of ground fault is small, so the fault line selection problem has not been commendably solved, which affects the reliability of power supply. As an important aspect of power system, with the increasing of nonlinear loads, power quality problem has been more and more concerned by electric power departments and eletricity users, so it's very necessary to monitort power quality online.This paper designs a system, named LLJ-JDS, which is a distributed network. The system, whose platform is 32 bits digital signal processor, combines traditional line selection methods and capacitors injection method, and combines local line selection and concentrated line selection. It not only solves the problem of fault line selection, but also achieves the purpose of power quality monitoring. The system meets the power providers and users' urgent demands, so has good practicability and economic benefits.At the beginning of this thesis, the research status and related standards of fault line selection in non-effetive earthed system and power quality online analysis are introduced. Then, the characteristics during single phase ground fault in neutral-point ungrounded system and neutral-point earthed via petersen coil system are respectively analyzed, and capacitor injection method is put forward. Technology requirements and basic algorithm of power quality monitoring devices are described in detail. On this basis, overall design of the system is brought forward, and stress is laid on the hardware and software design of the system's terminal. Finally, base on the situation of practical application and results of type testing, summery and prespect of LLJ-JDS system are proposed. |
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