Protection of high-voltage AC cables

High-voltage underground ac cables have signiflcantly different electrical characteristics than overhead transmission lines. The cable sheath or shield grounding method has a major impact on the zero-sequence impedance of underground cables. Understanding how the underground cable grounding method affects the series sequence impedances is very fundamental to underground cable protection. In the paper we briefly discuss the types of underground cables, their bonding and grounding methods, and the fundamental differences between overhead transmission lines and cable electrical characteristics. Finally we discuss the application of short-circuit protection for highvoltage ac cables.