输配电装备及系统安全与新技术国家重点实验室自主研究项目(2007DA10512709301);中央高校基本科研业务费资助项目(CDJXS11150020);Project Supported by Scientific Research Foundation of State Key Lab. of Power Transmission Equipment and System Security(2007DA10512709301);Project Supported by the Fundamental Research Funds for the Central Universities(CDJXS11150020)