Study on wide-area backup protection system for the smart grid

A graph theory based wide-area differential backup protection system which can be used on smart grid is proposed. By means of graph theory, the dynamic online partitioning of protection zones is implemented. Then through current differential calculation in the protection zones obtain the protection criterion and complete the protection function. The system implements primary and backup current differential protection in the whole grid by expanding the protection zones step by step. The system is composed of line protection and bus protection. The bus protection designing in different connection mode and the coordination of line protection and bus protection is considered. The protection system has high selectivity and reliability through simulation verification.