Distributed Energy Resources and Renewable Energy in Distribution Systems: Protection Considerations and Penetration Levels

Distributed Energy Resources (DER) including renewables of various designs and ratings have become increasingly common in the last decade. Many States and the Federal government have passed Laws mandating a certain amount of energy be generated using renewables and/or alternative fuels that lend themselves to smaller power plants being connected to the utility system at the distribution level. Power electronics have also made substantial progress allowing inverter-connected smaller power plants with diverse types of fuels to be interconnected with the grid. Optimization of overall electrical system performance at the distribution level is very important for the long-term economic viability of DER systems. It is becoming more important to understand the integration of these systems with the existing electric power system. This paper will address the system integration and utilization issues associated with DER including renewables and will examine protection considerations and penetration limits for DER in the existing distribution systems.