To be adaptable to smart dispatch, overall renovation of existing protective relaying fault information system of North China power grid is performed. The renovation scheme is analyzed in detail in system structure, communication protocol, information format and fault diagnosis. Firstly, according to the differences between newly built substations and renovated substations several typical system structures are conceived and proposed, and the necessity of independent networking for protection devices and fault recorders is analyzed. Then adopting proven technique and combining with related international standards such as IEC 61850 and so on, the speed and quality of information uploading are improved; based on the standard of extensible markup language （XML） the content of fault report and the format of HDR are standardized with detail to perfect device information and fault character information, thus in master station system the convenience in information filtering is swinging implemented. Finally, several different fault diagnosis methods are explored to improve overall operation level of this system. Actual operational experiences of several months show that the proposed renovation scheme for existing protective relaying fault information system is reasonable and effective.

This paper introduces the basic principle of the synchronization of sample time,the synchronization of sample number and the channel time delay computation used in pilot current differential protection using the digital channel,compares the difference of protection performance of adopting different synchronization methods,and deeply researches the influence of channel time delay change on differential protection brought by the switch process of double longitudinal channel in different switching modes.Through the study,this paper makes it clear that the synchronization of pilot current differential protection is incorrect in a period after the channel switching or in the switching process,and the countermeasure of protections must be considered,otherwise,false tripping would occur.

With the development of southern Beijing-Tianjin power grid, the problem of security and stability caused by the power grid structure has great influence on the operation of the whole Northern China power grid. The stability control system for the southern Beijing-Tianjin power grid consists of 14 stations, covering Langfang, Tianjin, Beijing area. When serious fault occurs on the power receiving section of southern Beijing-Tianjin power grid, including Dafang double circuit lines, Fangbao line and Baoba line, generator tripping and load shedding should be done to ensure the stability of the power grid. The research and application of the stability control system for southern Beijing-Tianjin power grid is introduced in this paper. The key technology of regional stability control system is generalized, which is helpful and meaningful for its future application.