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Zhang W.,Jicheng Electronics Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

Fault judgment criteria independent of operation mode is proposed to solve the problems of fast removal of the fault and avoiding re-tuning of device parameters in the operation mode changes. A distribution network switch group model is established, based on which and relying on fault currents and active power direction, the criteria is converted to a series of logical operations. Logical value of a switch and the logic of the switch group value are calculated, and the logical value of the switch group is used to calculate the action of each switch logic value. Using this method, distribution network open/closed loop operation mode are analyzed in detail. For temporary failure, the coincidence mechanism is introduced which does not depend on the communication side of the switch voltage, effectively avoiding the fault isolation scope expansion in the exceptional circumstances of the communication. A grid distribution network with 4 mains and 15 disconnected switches is taken as an example when two failures simultaneously occur. It demonstrates the feasibility of the proposed method.


Zhang W.,Jicheng Electronics Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

A short-term load forecasting method is made based on the load curve shape similarity and human comfort index for distribution load characteristics. The characteristics of the load curve shape similarity are researched. Based on the expectation of each moment load difference, a load curve shape similarity calculation method is given. Based on the impact of meteorological factors on the load, a human comfort index is introduced, and according to the daily maximum temperature and minimum temperature, the similarity calculation method of a day human comfort index is given. According to the distribution load type characteristics, the load change characteristics of various types are researched on holidays and normal working days. Combining these features, this paper gives a distribution network short term load forecasting method, and discusses the method and its steps in detail. Nine days of historical data and weather data of a distribution network power point are taken as examples to verify the feasibility of the proposed method.


Zhang W.,Jicheng Electronics Corporation | Leng Y.-J.,Jicheng Electronics Corporation | Yan J.-F.,Jicheng Electronics Corporation | Yao D.-P.,Jicheng Electronics Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

To solve the issue of distribution network operation comprehensive status assessment, the concepts of minimum distribution island and minimum distribution subnet are proposed. Five levels of minimum distribution subnet operation state are given. A detailed analysis of the characteristics of each state is made. Based on minimum distribution subnet, index score of each state in the subnet and the corresponding formula are given. In accordance with the precautionary principle, the running state and index score of the worst distribution subnet are regarded as the entire distribution network operations and index score. Based on improved radar chart analysis, a description of the five state levels of concentric circles drawn is given. In accordance with the current status assessment indicator, 15 minutes status assessment indicator and 60 minutes status assessment indicator, combined with the radar chart area and perimeter, three distribution network status assessment indicators are presented. The characteristics of the three indicators are analyzed with an example. The example analysis shows that the proposed method is feasible. The case research shows that the proposed method can clearly reflect the reaction operating status of the distribution network. It provides a reliable basis for real-time operation of the distribution network, and has good practical significance.


Zhang W.,Jicheng Electronics Corporation | Xu S.-H.,Jicheng Electronics Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

To improve the reliability of distributed feeder automation fault location, a distribution network switch group model is established. Based on switch group model, the failure process due to switch rejecting is researched. The fault handing principles are proposed based on logic operations. By supplementing the principle of single-shot reclosing, the extension of fault isolation scope is avoided effectively when the switch rejects to break. Through analyzing the switch rejecting to close, a secondary reclosing processing method is proposed to avoid fault isolation extending. The fault handling process is researched in three cases of communication failure of the adjacent switch. A uniform failure determination method is given. Incidental interference and permanent failure are discussed in switch protection signal failure. The research shows that incidental interference has no effect on fault isolation, while permanent failure will expand the scope of fault isolation. The results of many cases study show the feasibility and effectiveness of the proposed approaches.

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