Distributed Location Technology For Single Phase Earth Fault In Non-solidly Earthed Network

At present,the research on the small current earth fault mostly focus on the local location algorithm and centralized location algorithm.The local location method is easy to implement,but only uses the local information which is limited.So the control performance is not perfect.The centralized location method based on the master station can optimize the control performance with the use of the global information,but it involves many links and the response speed is slow.Distributed control can not only use the measurement information of multiple sites to improve the performance of protection and control,but also avoid the long delay of communication and data processing caused by centralized control of the main station.The application of the distributed control in the short circuit fault processing provides a new idea and new direction for the fault location of the small current earth fault.In this paper,the adaptability,of existing distributed fault processing technology for small current earth fault processing,is studied and analyzed from the aspects of system structure,dynamic topology identification,communication configuration and basic working mode.Secondly,a small current earth fault transient equivalent circuit which is suitable for distributed fault location is established.The correlation coefficient,for the transient current waveform,the transient current effective value and the ratio of the transient current peak to the steady current amplitude,are theoretically analyzed and deduced in the small current earth fault.A distributed location algorithm based on the correlation coefficient for the transient current waveform,the transient current effective value and the ratio of the transient current peak to the steady current amplitude is proposed.And the adaptability of the method is analyzed.Thirdly,the characteristics of transient power direction,the polarity of the maximum of transient current,the phase of steady current and attenuation DC component are analyzed and calculated.Two distributed localization algorithms for small current earth fault based on the attributes of monitoring points are proposed.The two methods include the fault location algorithm,based on the transient power direction,and the fault location algorithm,based on the steady state current phase and the maximum polarity of the transient current.And the adaptability of the method is analyzed.Fourthly,the MATLAB simulation platform is used to verify the proposed method systematically.Lastly,the performance of the proposed distributed algorithm of fault location is analyzed and compared.The results show that the distributed location algorithm is superior to the centralized location algorithm and the local location algorithm.The distributed location method based on monitoring point attributes is less pressure and the effect in positioning is better in distributed location algorithm.Through the work of this paper,the shortcomings of existing localized and centralized small current earth fault location methods are made up,which promotes the development of the distributed control in the small current earth fault location.It is of great significance to improve the earth fault handling technology and power supply reliability of distribution network.