Overvoltage analysis and protection of lightning arresters in distribution systems with distributed generation

The objective of this paper is to address an issue that arises from the increasing penetration of distributed energy resources in power systems: the design and analysis of protective devices with more complex topology and power flow patterns. In particular, this paper investigates lightning arrester overloading and failure from fault induced overvoltages. Currently, the length of time from the fault inception until the lightning arrester's failure is unknown, forcing utility companies to assume the worst-case scenario and install more costly and complex protection schemes than might otherwise be needed. In this paper, the Thevenin Equivalent Impedance method is proposed to analyze a distributed generation (DG) source's effect on the transformer high side voltage. After examining the voltage transients and determining the magnitude of the overvoltage, an optimal and cost-effective protective relaying strategy is developed and implemented. To complete this study, various types of DG sources were modeled and simulated using two test systems. Finally, the implementation of the suggested solution of intentional islanding operation of the distribution system is discussed. This solution allows the DG source to continue to supply a portion of the distribution system's load, thereby increasing the reliability of the system.