The insulation of components and devices in high-voltage technology is of vital importance and is often the decisive factor in design and construction. Knowledge of the physical processes which limit the electric strength of an arrangement is essential for economical manufacture and reliable performance. The development of high-voltage insulation technology since the beginning of this century has produced very different solutions for diverse insulations. Characteristic terminology is frequently used pertaining to specific devices, and this often obscures the clear view of the basic scientific principles. Manifold solutions, as a consequence of different properties of the working materials, also impede the understanding of common ground. This book is principally intended for students of electrical engineering who, towards the end of their course, aim to pursue the difficult path of applying their fundamentals to practice. Very often one has to be satisfied with a solution comprising rough approxi- mations and simplifications, yet one must not lose sight of the basic prinCiples because knowledge of these and their proper application are prerequisites for further development in virgin technological territories. In full consciousness of this continuity Prof. Dr.-Ing. E .h. Hans Prinz, our mutual academic tutor at the Technische Hochschule Mtinchen, trained his students accordingly. We are honour-bound to gratefully acknowledge this in these pages.