Facing the growth of energy demand and the worldwide interests in renewable energy sources, smart grid has been proposed in order to accommodate the needs of power grid development. In China, digital substations have been widely applied. Moreover, as the worldwide interest and development in smart grid have increased significantly, the digital information availability and communication capability of modern substation have been improved. Different with traditional substation protection configuration based on local information, Integrated Protection (IP) is used to denote the integration of several protective devices for multiple power equipment within the substation into one protective relay, obtaining all the real time information of the substation by communication network. The analysis of sharing information and cooperation among different protection functions helps to realize more reliable and sensitive fault detection. This paper describes several different integrated protection schemes and their respective advantages and disadvantages. The principles and functions applied in integrated protection systems are addressed to provide an overview of the current state of the technology. A new coordinated protection system based on inter-substation information is proposed and simulation study is discussed to verify the improved reliability and sensitivity.