Calculation of Power System Overvoltages

This chapter presents a short description of the main causes and methods for limitation of overvoltages. It discusses the analysis and calculation of typical overvoltages. The chapter provides the modelling guidelines to be used with any class of overvoltage, a description of the phenomena that cause overvoltages and some illustrative cases. Standards distinguish several classes and shapes of overvoltages: temporary overvoltages (TOV), slow-front overvoltages, fast-front overvoltages and very-fast-front overvoltages. The chapter outlines the analysis and simulation of the most frequent causes of TOVs in power systems. Switching transients in power systems are caused by the operation of breakers and switches. The switching operations can be classified into two categories: energization and de-energization. Lightning strokes are one of the primary causes of fast-front transients in power systems. Very fast transients (VFT) in gas insulated substations (GISs) can arise any time there is an instantaneous change in voltage.