The problems encountered with such high voltage transmission lines exposed to nature are electrostatic fields near the lines, audible noise, radio interference, corona losses, carrier and TV interference, high voltage gradients, heavy bundled conductors, control of voltages at power frequency using shunt reactors of the switched type which inject harmonics into the system, switched capacitors, over voltages caused by lightning and switching operations, long air gaps with weak insulating properties for switching surges, ground-return effects, and many more. The important topic of EHV cable transmission up to 1200 kV is gaining ground with oil-filled, PPLP, XLPE, and SF6 insulation. The book covers all topics that are considered essential for understanding the operation and design of EHV ac overhead lines and Underground cables. Theoretical analyses of all problems combined with practical application are presented in detail. EHV laboratory equipment and testing are fully covered together with application of digital recorders, fibre optics, etc. for impulse measurements. Every chapter contains many worked examples in order to illustrate and reinforce the theory. All examples are taken from practical situations as far as possible.