Protection Scheme for Active Distribution System Based on Directions of Current Phase Angle Variation

With the increasing interconnection of distributed generators(DGs),the radial structure of conventional distribution system will change to multi-terminal.Because of the randomness of the DG power output,the traditional protection scheme based on the current amplitude is difficult to set.The difference in phase angle between the currents before and after fault conditions is investigated,and the relationship between the direction of current phase angle variation and fault location has been found to present a new current directional pilot protection scheme.This scheme uses only current information to avoid the installation of voltage transformers.For a huge distribution network,this scheme leads to a very high economy coefficient.As it only needs transmitting the determination result signals,the demand for the communication channel is reduced.Finally, verification of the protection scheme is carried out by simulation analysis.