A novel method of current-only directional overcurrent protection

As more and more distributed generations existing in the grid, the directional overcurrent protection is required in the modern distribution network. The traditional method needs the voltage phasor as the reference that adds the cost. The current-only directional overcurrent protection can solve this problem to a certain extent. But, it can't recognize the fault direction when the direction of power flow is not fixed in the normal situation. This paper proposes a novel method that utilizes the information of the current flowing in the cable shield to overcome the drawbacks of previous current-only directional overcurrent protection.