Reliable and resilient future grid through T&D co-simulation and improved distribution systems protection using traveling-wave relays

Abstract

Over the past century, US electric grid has evolved into an extremely complex and large interconnected grid identified by the National Academy of Engineers (NAE) as the greatest engineering achievement of the century. During that period, the overwhelming accepted principle was “larger or bigger the better”. The AC transmission voltage went up to 765 kV and the individual generating units were in excess of 1,000 MW. This centralized generation model was considered to be efficient and reliable way to operate the grid. This grid continued to serve the nation well. It, however, faced serious challenges with the demands of the 21st century that will require high penetration of renewable energy, environmental impact of large power plants, global warming and climate change, carbon emission and global energy sustainability. New approach had to be taken to adopt the new regulatory policies. Emerging trends such as low-cost natural gas, increased deployment of renewable energy technologies in distribution, and continued evolution of electricity markets are transforming the ways to generate and deliver electricity. Other factors such as environmental policies to reduce the carbon footprint, maximize the energy efficiency by utilizing the distributed based renewable energy generation also influence the future grid structure. Aging infrastructure combined with the growth and the evolving de-centralized model will have significant impact on the future grid’s ability to provide the electricity more efficiently, reliably, with higher resiliency. This dissertation is divided into two parts: (1) to achieve greater resiliency, it proposes an integrated T\&D co-simulation framework that considers the effects of Distributed Energy Resources (DER) in the distribution. (2) to achieve greater reliability, improved system protection is needed at the distribution level that considers the DER affect such as two-way power flow, low fault currents, etc. This dissertation proposes and analyzes the travelling-wave (TW) based protection at the distribution level. Integrated T\&D framework and the TW based protection improves the grid to be more reliable and resilient.