This book addresses the structure and application of expert systems in technical systems, using examples from electrical power supply. After a historical overview of the emergence and use of expert systems, the fundamentals of predicate logic as the foundation of knowledge-based systems are explained. The basic principles of knowledge-based systems, knowledge acquisition, and knowledge storage are discussed, along with selected intelligent techniques. Numerous illustrative examples from the field of electrical power supply are provided to explain the specific challenges of designing expert systems in this context. The work is primarily intended for students and engineers in technical disciplines, particularly electrical engineering, who are seeking an introduction to the topic.