ABSTRACT
Underground cables can supersede overhead lines for electric power transmission over short distances. Cables are usually more expensive than overhead lines at all supply voltages, with a cost ratio of about 20, 8, and 2 at 400, 132, and 11 kV, respectively. This chapter provides the many aspects of AC high-voltage cables, with particular emphasis on fundamentals. Insulating materials for power cables are generally classified as impregnated paper, synthetic materials, and compressed gases. Cable insulation used to be oil-impregnated paper, with oil under high pressure in high voltage (HV) and extra high voltage (EHV) cables. Three-core belted cables use impregnated paper wherein each of the conductors is insulated for half of the line voltage. The breakdown strength of the cable dielectric is greatly influenced by the time span during which the voltage is applied. A voltage pulse from a suitable source is applied between the faulty conductor and a sound conductor or the metal sheath.
