Research on the electric unbalance degree of multiple transmission lines non-parallelly erected entirely in one common corridor

Abstract

When multiple transmission lines are not entirely parallel erected in one common corridor, the electric unbalance degree of double-circuit ultra-high voltage (UHV) AC transmission line can be affected by several factors, such as severe electromagnetic coupling between lines in parallel section, various phase sequence arrangements and transposing modes of the lines, active power of the lines changing constantly. This paper presents a detailed analysis on the electric unbalance degree of double-circuit UHV AC line in common corridor, with particular attention to the effects of the parallel section’s length, number and the active power of the lines. The causes and factors of unbalanced currents of double-circuit UHV AC line were taken into account by phase-sequence conversion of current and voltage, and the above effects were proved by an actual example. The main factors were studied by simulating in PSCAD/EMTDC. The results show that the parallel section’s length, number and the active power of lines have considerable influences on the electric unbalance degree of double-circuit UHV AC line in common corridor. Finally, some suggestions have been proposed to provide as a construction reference to confine the level of electric unbalance degree of double-circuit UHV AC line which is not entirely parallel erected with other lines in common corridor.