To achieve the highest level of availability and cost-effectiveness the steam turbine generator set in power plants must be operated professionally at optimum thermodynamic performance. The modern I&C equipment (Instrumentation & Control) of Siemens Power Generation (KWU) and the on-line diagnostic system DIGEST help accomplish this by providing a comprehensive overview of the operating status and by analyzing the condition of the steam turbine generator set during operation. This equipment enables the early detection of incipient faults and lowers the burden of the operating crew. This book provides a broad overview of the state-of-the-art of I&C equipment and the use of diagnostic systems. The target group for this book are power plant operators, planning engineers and consultants.