Protection of distribution systems with distributed generation using current phase variation

With the increasing attention to the penetration of distributed generation (DG) in the distribution system, it has become important to propose an appropriate protection strategy that is effective in the new condition. Since the power output of DG is intermittent, the traditional protection scheme based on definite or inverse time overcurrent relays is not suitable to distribution system with DGs. This paper investigates the phase angle difference between the currents during fault and pre-fault conditions. And the relationship between the current phase angle variation and fault location has been found to present a new type pilot protection scheme. This scheme uses only current information to avoid the installation of voltage transformers. For a huge distribution network, this scheme is economical. As it is only needed to transmit the determination result signals, this reduces the demand to the communication channel. Finally, a verification of the protection scheme is carried out by the simulation analysis.