Research On Protection Of Medium And Low Voltage Distribution Network With Distributed Generation

Distributed generation is developing rapidly with its advantages in terms ofresource utilization and environmental protection in the world, which, as a usefulsupplement to the large centralized power grid, has become an inevitable trend inthe development of power system around the world. However, the characteristics ofthe distribution network failure has been changed after DG is connected to thedistribution network, which brings about a variety of effects on distribution networkprotection. First, muti-terminal power change the direction of the fault current,andthe part of current protection will be reduced in sensitivity or lose the selectivity.Besides, the uncertainty of fault current may be increased for the volatility andintermittent of photovoltaic, wind and other types of distributed generation as wellas the start and stop of it in the integration of high shares of distributed generation.What’s more, the operation and fault characteristics of distributed network, whichis connected with DG via an inverter, are very different from the traditionalgenerator. All these contributes to reducing its original adaptive distribution or evenits failing to correctly identify and isolate the fault.After that, this essay studies in depth the failure characteristics of thedistributed generation, starting from doing research on the principle of varioustypes of DG and its methods that connected to the grid. By controlling the type andcharacteristics of distributed generation inverters, it also draws its equivalent modelwith the analysis of the transient output characteristics under fault. In addition, it also offers the detailed analysis of the impact of the number ofdistributed generation, its capacity and the access to the original location. Also, itstates clearly the influence of transformers in distributed power grid and theselection of grounding on ground current protection and points out reasonablealternatives, combining the low voltage distribution network operation and differenttypes of wiring. Analyzing the impact of distributed power on the cooperationbetween protection and automatic reclosing and proposing solutions are part of thearticle as well.It puts forward protection setting optimization raised by a single DG line and Tline and network access with examples on the basis of the analysis of problems inthe existing protection, and then raise an adaptive protection scheme combined withexamples of simulation when integrating high shares of DG in the same wiring.Finally, a combination of grid-connected photovoltaic industrial park instance，proposed protection configuration design, and simulation analysis of the impact ofmultiple DG connected to the grid of the original line protection, and verify thefeasibility of adaptive protection.