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Fan Y.,Xinjiang University | Zhong X.,Xinjiang University | Chang X.,Xinjiang Communication Center for Power Dispatching | Wang H.,Xinjiang Communication Center for Power Dispatching | Zhou Z.,State Grid Corporation of China
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2015

With the impact of grid structure, generators distribution, generator units parameters, and load type, the system's frequency characteristics presents temporal and spatial distribution. However, system frequency is the reference for formulating the UFLS scheme, which makes the action of UFLS device unsatisfactory. Based on the grid splitting in some region, this paper analyzes the dynamic characteristics of system frequency and the action of UFLS device in detail under the power shortage. Considering the impact factors such as frequency recovery effect, load shedding values and its types, etc., it studies the influence of load characteristics on frequency and proposes two research programs including decentralized load shedding and centralized cutting industrial load of large consumer. The research results show that cutting industrial load of large user can quickly restore the system frequency and have smaller influence on the residents' load, therefore it has significant reference value on control strategy of frequency recovery in the grid operation and making the program of the UFLS. ©, 2015, Power System Protection and Control Press. All right reserved. Source

Zhou Z.,Xinjiang University | Yao X.-P.,Xinjiang University | Yao X.-P.,Xinjiang Communication Center for Power Dispatching | Wang W.-Q.,Xinjiang University | And 3 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

With the increasing of grid electricity load and transfer power, power grid is also strengthening, which leads to the emergence of looped network and a grid structure of higher voltage level. Because the space truss construction of high voltage level is still in initial stage, grid structures of electromagnetic loop network appear in many places. Electromagnetic looped network frame is beneficial for the increase of power supply reliability of power grid. But looped network operation has its shortcomings in the aspects of the protection configuration, the power transfer caused by normal looping-off of looped network and fault, operation line overload and so on. When the multi-terminal active looped network is opened, the power is transferred, which has effects on supply network, including the setting of automatic safety devices, operational control and accident handling. To analyze the power distribution in advance after the opening of the looped network is very important for arranging operation modes, handling accidents, setting the automatic safety device, preventing accidents from enlarging and ensuring the safety and stable operation of the looped network. Based on the analysis of power transfer of the opening looped network, the paper also offers the definition of power transfer ratio and the factors which affect power transfer. Some precautions about power transfer after the opening of the looped network are provided. The PSASP procedure is used to analyze looped network in the way of analog simulation, which proves the correctness of the related conclusion. Source

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