The present disclosure relates to real-time data management for a power grid and presents a real-time data management system, a system, method, apparatus and tangible computer readable medium for accessing data in a power grid, a system, method, apparatus and tangible computer readable medium for controlling a transmission delay of real-time data delivered via a real-time bus, and a system, method, apparatus and tangible computer readable medium for delivering real-time data in a power grid. In the real-time data management system of the present disclosure, a unified data model covering various organizations and various data resource is designed and a management scheme for clustered data is used to provide a transparent and high speed data access. Besides, multi-bus collaboration and bus performance optimization approaches are utilized to improve efficiency and performance of the buses. The real-time data management system may also include an event integration and complex event process component to provide a credible prediction on status of the power grid. With embodiments of the present disclosure, it may efficiently manage the high volume of real-time data and events, provide data transmission with a low latency, provide flexible extension of both the number of data clusters and the number of databases to ensure high volume data storage, and achieve a high speed and transparent data access, Additionally, it also enable the rapid design and development of analytical applications, and support the near real-time enterprise decision-making business.