Application of enhanced dual-channel line differential protection in China Southern Grid

In 2008, very rare icing disaster suffered China Southern Grid (CSG). Many transmission lines, substations and ground lines are outage. Measurements had been taken to keep main grid working safely and stably. The experience, especially on protection field, absorbed from this case is introduced in this paper. By complement of public communication network, electric communication is strengthened. To overcome the difficulty that public communication channel can´t be used in differential protection, three types of improved differential protection relays are developed. The principle of those relays is explained in detail. In 2012, CSG experiences another ice disaster, the new type protection works perfectly.