I. Introduction
The data of smart grid phenomenally increases, and almost all of nuclear power stations collect a large amount of data from wireless sensors, distribution network equipment, and even communication objects interacting with consumers. It is quite challenging to process such massive, multi-source and redundant data using existing technologies. In fact, only a partial set of massive data is meaningful to executing one task in the smart grid. Without effectively extracting useful data from huge information, the processing and decision of the corresponding task will be severely delayed. Therefore, data extraction becomes very important to improve the computing efficiency in temporal dimension.