This course provides an in-depth study of power quality and reliability in modern electrical power systems. It examines the technical causes and impacts of voltage sags, swells, harmonics, flicker, frequency deviations, and power interruptions, along with methods for their analysis and mitigation. Emphasis is placed on maintaining stable and high-quality electricity supply in generation, transmission, and distribution networks. Students will explore reliability assessment techniques, including probabilistic modeling, contingency analysis, and standard reliability indices such as SAIFI, SAIDI, and CAIDI. The course also addresses the influence of renewable energy integration, distributed generation, and power electronic devices on system performance and grid resilience. Through analytical tools, case studies, and computational simulations, learners develop practical skills to evaluate system adequacy, improve operational reliability, and implement effective power quality solutions. The course equips future engineers and energy professionals with the technical competence required to design and manage sustainable, reliable, and resilient power systems.