Study On Zoning Protection Scheme For Distribution Network Considering Wind Power Distributed Generation

With the emergence of the global energy crisis, environmental pollution, as well as defects of the traditional centralized grid power generation mode, the distributed generation (DG) technologies have been rapid developed. The distributed generation technologies include wind power, photovoltaic, fuel cell, biomass generation technology and so on. The access of distributed generation, especially wind power distributed generation, may cause traditional protection not to operate correctly, as the result of changed radiating structure and power flow distribution. The impacts on current protection of distribution network connected with wind power DG and zoning protection scheme need to be researched in this paper.First of all, the model of wind power DG and its operation characteristic simulation analysis were established by the PSCAD/EMTDC simulation software. In the model, the wind power DG is accessed to an infinite power system. Through the simulation experiments, the operation output performances of wind power DG are analyzed on the wind speed disturbance and fault in side of system. The output of wind power DG is random, can not be used the form of the constant power series impedance equivalent.Secondly, the influences that wind power DGs are accessed to distribution network current protection have been researched, as well as the countermeasures. The short circuit current calculation formulas under different fault in a distribution network with wind power DG are derived and analyzed. The access of wind power DG makes the current of the downstream protection increase, the upstream protection will flow reverse current. The influence of DG layout mode, access capacity, wind types and fault time to the current protection was analyzed by the simulation experiments.In order to ensure the protections can still correct cooperation after DG connected, the DG access capacity must be limited, that focused on two aspects. Firstly, as the increased current of DG, leading to expansion of the downstream protection, in order not to make the scope of protection extends to the downstream lines, resulting in losing selectivity with the downstream protection, the DG access capacity has a limit values; secondly, when the fault occures on the DG upstream line, the DG will provide reverse current to the upstream protection. the access capacity of the DG has a limit, that make the reverse current not exceed the Ⅱ zone protection setting value of the upstream line. Considering these two aspects, the smaller of the two limit values is choosed as available access maximum capacity of DG. For a10kV distribution network with wind power DG, obtained the access maximum capacity of DG. The simulation shows that the more distribtued with DG layout, the smaller impact on fault current, but the DG total access capacity can be increased. A kind of zoning protection scheme for distribution network with wind power DG has been researched. According to the wind power DG access location, the capacity and load distribution network, the whole system is divided into several sub-areas. Using distribution automation system and intelligent measurement and real-time monitoring and online analyses function of control protection device of. the fault location algorithm is researched, based on network structure matrix for distribution network with wind power DG distribution network. The fault location algorithm uses the network associated matrix and failure interval judgment matrix, to find the fault location with the criterion.The fault isolation and recovery strategy is provided. The validity of the fault location algorithm and fault isolation and recovery strategy are verified by the examples.