Abstract. Fault diagnosis expert system obtains the operation of power grid by monitoring the change of dynamic database. While all kinds of measurement, switching value and a part of status records and documents about the status of power grid operation transferred by fault information system and SCADA system are stored in the dynamic database. As the change of power grid operation state and the passage of time, we update the contents in the database. Once the failure and abnormality occur, the fault diagnosis expert system is started, so we can judge whether start core diagnostic program by starting detection. If the program starts, the whole diagnosis process should be under the unified dispatching. We can obtain the related information about the fault diagnosis continuously from dynamic database so as to form our own information chain and begin to carry out the reasoning. Finally, we make the diagnosis results be displayed to the dispatcher in a specified format so as to make the diagnosis results be as the reference of fault recovery processing.

The paper analyzes the influence of user lateral grid-connected PV generation on relay protection of distribution network, and proposes the opinions for the economic technique and selectivity of protection. The paper applies DIgSILENT PowerFactory software to make simulation calculation and analysis on the actual projects, and proposes relay protection allocation scheme and protection setting rules, which provides engineering references for the grid-connected PV power projects.