直流电缆上交流分量的计算及其屏蔽

Calculation and Shielding of AC Component on DC Cables

交直流电缆并行敷设时,交流电缆会在直流电缆上产生感应电动势,进而产生工频电流分量。为此,针对上海柔性直流输电工程中可能的几种敷设方式下,对交流电缆在直流电缆上的感应电动势进行了计算,并且实测了不同接地方式下直流电缆金属屏蔽层对交流分量的屏蔽系数。计算结果表明,不同的敷设方式下交流电缆在直流电缆上产生的纵向感应电动势不同,三相交流电缆对直流电缆电磁耦合距离的不同是产生纵向感应电动势的根本原因;计算结果还发现在三相交流电缆与直流电缆耦合距离越远,所产生的纵向感应电动势越小;在4种敷设方式下,耦合距离超过2m后纵向感应电动势趋近于0。最后,还给出了实际工程中考虑屏蔽效应的直流电缆上感应电动势的计算方法,并且提出了屏蔽直流电缆上交流分量的方法。

When AC and DC power cables are laid in parallel,the induced electromotive force and power frequency current component will be generated in DC cables.The induced electromotive force is calculated with different layout in Shanghai HVDC project.The DC cable shielding factor is also measured in different grounding methods.The result shows that the difference of induced electromotive force under different layout is caused by different electromagnetic coupling distance between three phase AC and DC cables.The further the coupling distance,the less induced electromotive force is.The testing results show that induced electromotive force is close to zero when the coupling distance exceeds two meters in all four kinds of layout.The induced electromotive force calculation method considering DC cable shielding effect is proposed and method to shield AC component in DC cable is also described.