Direct-current transmission line protection method and system based on pure current characteristics

The invention provides a direct-current transmission line protection method and system based on pure current characteristics. The method is characterized in that a current difference value and a current break variable of a line are determined by collecting the current of a direct-current transmission line, and whether a preset protection criterion is established or not is determined according to the current difference value and the current break variable of the line, so that whether the direct-current protection action is outputted or not is determined. The method is advantaged in that the action speed of metallic fault protection can be further increased, the action speed of high-resistance fault protection is greatly improved, protection is reliable and does not act when lightning strokeor abnormal large number occurs, the protection of a non-fault pole line is reliable and does not malfunction under a single-pole grounding fault working condition, and protection performance of thedirect-current transmissio