1. The positive-sequence fault components based directional relay is a new type of unit for recognizing fault direction.

2. The scheme includes the transverse differential protection, the directional relay action on negative sequence power of fault component and the incomplete differential protection.

3. The zero sequence directional relay is an important relay component for transmission line.

4. A reliable digital directional relay based on positive sequence compensated voltage and current is proposed, which can be used on HV transmission lines as main protection.

5. A novel signal processing tool, mathematic morphology (MM), is introduced to improve the performance of fault transient based ultra-high-speed directional relay.

6. Analysis shows that the voltage operating dead zone is small and have more sensitivity than traditional power directional relay.

7. Based on the method of six sequence fault component, this paper analyses the performance of zero sequence directional relay on double circuit line on the same pole (DLSP).