The Research Of Grounding Protection Based On Fuzzy Clustering For Ditribution Systems

Neutral ineffectively earthed systems are widely operated in medial and low voltage distribution networks of China,when single phase ground fault occurs in the neutral ineffectively earthed systems,it’s rather difficult to identify the fault feeder because the fault current is very small,especially under the effects of disturbance and determination error,so a novel protection method with high precision is always an important research task.On these problems,the mechanism and feature of single-phase fault occurred in neutral ineffectively earthed networks are discussed in this paper, the advantage and disadvantage of some typical protection methods are analyzed both in steady process and transient process.Because the single fault protection method is with poor precision of ground fault detection and narrow application range,the novel clustering protection method is presented,meanwhile the derivation and analysis of fuzzy C means clustering algorithm are made in detail.Then in order to get the original sample matrix of cluster analysis,the simulations of some typical protection methods are carried out by EMTP. Finally a novel protection method that based on fuzzy clustering is introduced,in this method fault line and non-fault line are clustered by the differences among some fault characteristic parameters, then the category of unknown fault line is estimated by Euclidean distance,the protective settings are no need to change by the system operating mode.The clustering process is simulated by MATLAB,the simulation results shows that the fuzzy clustering protection method has high reliability.As stated previously, this clustering protection method has the advantage of non-setting protection and the fault feeders could be identified accurately, it is likely be widely used in distribution networks.