Study On The Electromagnetic Induction Of AC Cable Lines To Parallel DC Cable Lines

With the increase of the electricity load and the development of urbanization in China,more and more electricity load needs to be transmitted by power cables.At the same time,with the expansion of city and the consideration of city space and cityscape,more and more overhead lines should be replaced by power cables,which makes underground cable transmission lines more intensive and line coupling problems become more serious.Although the cable structure has better shielding properties than that of bare wires,due to the limited space of underground cable tunnel and the close distance between cable lines,line coupling problems are also obvious which can not be ignored.The parallel lines coupling on cable has not been studied fully and needs to be further researched.The basic principle of the electromagnetic coupling and coupling parameters are illustrated in this paper.A model of double-circuit AC cable lines coupling single-circuit DC cable lines laid in the same tunnel is established to study the regulation of influence of AC cable lines voltage,AC cable lines current,the distance between AC cable lines and DC cable lines,and the parallel length on electromagnetic induction current,electromagnetic induction voltage,electrostatic induction current and electrostatic induction voltage.The DC biasing and the various reasons to cause it are introduced.The principle of the power current in the bipolar DC circuit induced by AC circuit decomposed into DC while flowing through converter is expounded.Model of single-circuit AC cable lines coupling bipolar DC cable lines laid in the same tunnel is built.The induced voltage in the DC circuit under different AC cable and DC cable laying plans is calculated and compared.According to the principle that the bias current is proportional to the induced voltage,come to conclusion that the laying combination and phase sequence corresponding to the minimum induced voltage is the best plan.The basic shielding principle of metal sheath is expounded,and the influence of metal sheath grounding mode,sheath resistivity,sheath thickness and sheath location on shieldingfactor are studied.The metal sheath grounding mode,sheath resistivity,sheath thickness and sheath location influence regulation on shielding factor while the AC circuit is running on50 Hz and 60 Hz are compared.