Rapid isolation of faults in power networks with distributed generators

There are a number of technical issues that arise with increased penetration of Distributed Generation (DG) into distribution grids. Among them, foremost are the problems related to protection. With the interconnection of DG, distribution network protection systems may encounter situations which were unforeseen when they were originally designed and therefore fail to provide the required safety for the public, workers and equipment. Current DG operating practices overcomes these problems by disconnecting of all distributed generators when a fault occurs in the distribution network. This practice, though satisfies most of the safety related concerns, foregoes the opportunity for improving the power supply reliability using DG.; This thesis proposes an agent based protection scheme for distribution networks with distributed generators. The distribution network is divided into several network segments. The relay agents which are located at boundaries of these segments can determine the direction of fault currents using the transients, generated by the fault. Fault directions determined by the relay agents located at different points of the network are combined to determine the faulted segment. A fault direction identification technique which uses wavelet coefficient of the measured line currents was developed for relay agents. These relay agents are also capable of making the decisions based on the local information when they are unable to communicate with each other. A Decision Tree based transient classification scheme is proposed to distinguish the fault disturbances from non-fault disturbances which occur in the system. The operation of the proposed protection scheme was validated through extensive simulations.