Studies of air breakdown began in the eighteenth century. Two names are pre-eminent: Franklin and Lichtenberg, although contemporaries were active. Franklin's work grew out of his interest in lightning a long spark while Lichtenberg drew tree-like discharges, now called corona, across the surface of a large cake of resin. These two men defined two broad approaches to the study of breakdown which are perpetuated to this day in experimental and theoretical work. In the late 19th century, the emergence of modern physics, exemplified by the work of Townsend and his successors, permitted knowledge of the process of ionisation to be applied to these phenomena. The two approaches were thus linked and another concept from the 18th century, the electric field, became established as paramount in all discussions of the subject.

Benjamin Franklin was born in 1706, and was fascinated in his youth by electrical phenomena. In 1732 he founded with his collaborators the Library Company of Philadelphia with the support of the Perm family, and achieved a new insight into electrical science with his definition of a 'single electric fire'. This is equivalent to the free-electron concept, and implies the principle of the conservation of charge.

High voltage systems are often subject to transient overvoltages of internal or external origin. The resultant surges travel along the transmission line and can cause damage to unprotected terminal equipment. Corona losses and the earth return path can attenuate and distort the surges, but the magnitude of the surge may still exceed the insulation level of the equipment. Surge arresters provide a limitation of the overvoltage to a chosen protective level. The superiority of the recently developed zinc oxide (ZnO) material over earlier silicon carbide (SiC) renewed interest and boosted the use of surge arrester protection.

This chapter reviews some aspects of insulation coordination and overvoltages on transmission networks. The purpose of insulation coordination is to ensure that the probability of insulation breakdown is limited to an acceptable value and that any breakdown is restricted to self-restoring insulation. It is based on computing the most severe overvoltages occurring on the network and relating these to the breakdown characteristics of the insulation through appropriate margins to obtain withstand voltages for the network components together with the statistical risk of insulation failure.

This chapter provides a general introduction to the vast subject of circuit breakers, interruption strategies, characterisation and performance evaluation of gaseous/solid insulation systems, the identification of strategic online condition monitoring (CM) methods and diagnostic techniques (DT) as applied to modern switchgear systems, before and post deregulation. Although it has only been possible to touch very briefly on these aspects together with certain related strategic issues including sub station control systems (SCS), also working networks harder and environmental matters, important strategic issues have been considered briefly and a generous listof references, including CIGRE electronic sources is included, which will enable the reader to explore this developing topic in greater depth.

This chapter discusses the different numerical analysis method for the determination of electrical field distribution in high voltage equipment. It discusses and compares the finite-difference method and the boundary element method.

Pulsed power originated with the invention of the Marx bank in the early 1920s, enabling the simulation of lightning strikes and switching operations on power system components. Between the 1960s and the beginning of the twenty-first century, the demands of high energy pulsed power applications have stretched Marx bank techniques enormously. Refinements of triggering and switching techniques, and control and exploitation of the stray capacitances in the systems, enable 100-200 ns rise times to MV levels and above with MJ of energy being stored and delivered. The requirements of exotic radiographic, e-beam and plasma pinch loads have demanded the use of pulse forming networks or lines interposed between the Marx and the load to provide the requisite pulse shaping and power levels. Meanwhile the rise time capability of low energy Marxes has been reduced to nanosecond levels as a result of developments in capacitor and switching technologies. The latest direction is now for the development of ultrafast high energy Marxes with adequately low inductance for direct feed of compact e-beam loads.Pulsed power has principally developed in response to high energy physics and weapons programme requirements; plasma drivers, x-ray drivers, magnetron drivers, laser drivers, ion beam steering and acceleration. However, the industrial application of pulsed power is increasing.