Analytical Research In The Arrangement Forms Of Supervoltage Cross-linked Cable And The Shroud Induced Voltage

摘要

This paper expatiates that different arrangements of cables will lead to different shroud induced voltage number from detailed calculation in the design of the first domestic 220kV supervoltage, large length, big section cross-linked cable transmission line.When cables' position are not changed, if the arrangement of three-phase cables is symmetrical, the phase difference among shroud voltages of different subsection cables will be 120° in the cable lines, whose shrouds are cross-linked. Because the amplitudes are equal, the potential difference between two earthing points is zero. Thus there will not be circle current within shrouds. At this time, shroud induced voltages in different subsection cables are at the scope of permited number. When the arrangement of cable is dissymmetrical, the sum of vectors of three-phase cables' shroud voltages is not zero, although the lengthes of different subsection cables are equal, so the potential difference between two earthing points is not zero. Thus there will be circle current within shrouds of cables. Then, shroud induced voltages in different subsection cables in the cable line are far beyond the permited number. To improve transmission capability, prolong use life-span of cables and supply electricity safely, it's quite necessary to prove the validity of concerned topic.