| The Distributed Generation technology is predicted to play an increasing role in power system of the near future in the light of its character of high efficiency, environmental. However, with the interconnection of distributed generation (DG), the distribution system has developed from the traditional simple single-source radial-network to complicated multi-source loop-network, bringing traditional feeder protection new problems in distribution network, such as sensitivity decrease, misoperation and malfunction, which deeply affects system operating and controlling. Therefore it is necessary to analyze the influence of the DG to the distribution network protection and propose its countermeasures, which is very useful to the development and practicality for the distributed generation technology.The different capacity, type and location of the DG source have different impacts on the current flowing through the feeder protection in distribution network. In this paper, improvement schemes are proposed in the light of the existing distribution protection, mainly including installing the direction element, modifying the setting value and using the longitudinal differential protection. Two new protection principles based on wide-area protection in distribution network are also proposed:â‘ the zoneâ… ,â…¡relay of direction and current protection on every line composes a communication unit with the zoneâ… ,â…¡relay of the next stage protection on the adjacent line at the upriver last line of DG, finally isolate the fault in the minimum section according to the result of the action of two stages protection.â‘¡Combining the direction information detected by the direction element at the termination of the line with section result divided by the current protection at the exit of the first line, exactly distinguish the fault section, ensure the upriver protection's selectivity and rapidity. Meanwhile the simulation of PSCAD/EMTDC verified the effectiveness of the scheme proposed in the paper.
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