Study On Fault Monitoring Method For Cyber Physical Distribution Network

The development and application of cyber physical system can promote the integration of distributed generation and the construction of power information.As two critical problem of developing smart distribution network,the high permeability of distributed generation and the heavy dependence on communication system interfere the protection and control of distribution network.Since the increasing integration of distributed generation,the traditional distribution with single source and radiant structure transforms into a complicated system with multi-power sources and uncertain bidirectional power flow.Especially,the infeed,outfeed and reversed current provided by distributed generation can severely lower the selectivity and sensitivity of protection devices.Moreover,although the advanced information and communication technology exert positive influence on the development of smart distribution network,sampling error,transmission error and the rejection of current breaker caused by abnormal communication system pose great threats to the safe and reliable operation of the whole system.In order to resolve these problems,this thesis studies on the protection method and fault identification method for cyber physical distribution network.The main research of this thesis is organized as follows:First,this thesis introduces the features and disadvantage of traditional over-current protection and automatic reclosure widely used in distribution network.And the mathematical analysis of influences on traditional relay protection caused by distributed generation is analyzed comprehensively.In addition,the negati-ve effects generated by abnormal communication system or distribution network is analyzed theoretically and simulated in detail.The above analyses and simulation provide great support for the design and research of protection scheme and fault identification method.Further,based on the traditional current differential protection,this thesis proposes the ideology of generalized node,and forms a novel protection scheme for distribution network.This method improve the operation criterion of current differential protection with the consideration of distributed generation,load and the distributed capacitance in cable line.In order to effectively resolve the problems generated by the integration of distributed generation,the rejection of breaker,sampling error and transmission error,this method establish the mechanisms of fault monitoring,generalized node establishment and extension,tripping confirmation and sampling error detection.Moreover,this thesis forms the matrix model of the mechanism of fault monitoring,generalized node establishment and extension,and introduces the communication architecture for the proposed protection scheme.Finally,based on the development of data mining technology,this thesis put forward a novel fault identification method based on local outlier factor detection(OFD)algorithm improved by ?-means clustering.Obviously,the nodes in fault area are definitely different from the normal nodes,therefore,this method utilizes the analysis results of ?-means clustering and OFD detection,and the OFD detection of generalized node,to monitor fault occurring in cyber physical distribution network.Compared to the traditional fault location methods,the proposed method makes it possible that the complicated relay setting calculation and comparison are not necessary for the fault identification,and can lower the data redundancy and enhance the data value.The proposed algorithm can not only identify where the fault occurs,but also locate the distribution network fault and faulted intelligent equipment.Hence,it provides an effective approach for the fault identification of smart distribution network.