Transient voltages affecting long cables

Long cables are subjected to lower lightning overvoltages than short cables due to the cable “self-protective” effect. This paper investigates the possibility of utilizing the full range of IEC impulse levels instead of the current practice of using the highest level. Calculated results of lightning overvoltages vs. impulse levels are provided for a cable inserted in an overhead line, for a number of cable types and system voltages. It is shown that for cable lengths that are of tens of kilometers it may sometimes be possible to even adopt the lowest IEC impulse level.