Differential Protection Based On EPON Communication For The Distribution Network With DGs

With the development of future distribution networks,Distributed Generation will be accessed in a large scale,which makes the phase current protection difficult apply to the distribution network with DGs.On one hand,the capacity,control strategies of DGs will have a huge impact on distribution networks;on the other hand,there are problems like scattered electrical information,simple communication conditions that still exist in distribution system with DGs.The differential protection strategy is under the guidance of the principles of sufficient protection,and research on the aspects of communication conditions and the protection criterion.Firstly,the article make a analysis on protection of traditional distribution networks and the differences on traditional distribution network relay protection after DG accessed,and put forwards the definition and superiority of sufficient protection principles.Compared to traditional relay protection,the sufficient protection strategy mainly focuses on the fault characteristics that can be identified.It is no longer necessary to protect the requirements for absolute selectivity for all fault conditions,but for the active distribution network in the vast majority of the failure of the common features to capture,which sacrifices the sensitivity and quickness of protection to achieve the low cost,high efficiency identificationidentification.Secondly,in order to solve the problems that DG accessed brings to distribution networks,differential protection is the best choice.However,the protecions' communication adopted a dedicated fiber channel or a multiplexing channel based on a synchronous digital hierarchy or a quasi synchronous digital hierarchy(SDH/PDH),which is costly and difficult to transformate.The EPON network combines the advantages of both Ethernet and passive optical networks,which have a natural advantage in the distribution network communication applications.With IEEE 1588 V2 clock synchronization algorithm,the synchronization accuracy can reach microsecond level,which meet the requirements of sufficient protection's precision.At last,the article put forwards the sufficient composite criterion of differential protection under the sufficient protection principles,which is combined current amplitude criterion and the phase differential protection criterion.Improving the performance of protection from two aspects of amplitude and phase difference,the sufficient composite criterion of differential protection has a recognition ability on most of the distribution network fault.Through the cooperation with DG bottom line removal technology and phase current protection,it achieved a full and multi-level security protection of distribution network with DGs.All the practicability,rationality and credibility were tested in the final simulation.