EMTDC Simulation Study Of Electromagnetic Coupling In DC Line Faults

With the development of HVDC transmission technology,The schemes of double circuits erected on the same tower have been adopted in many existing HVDC project.The projects that applying multi-circuit HVDC transmission lines on the same tower may bring about some new problems.Due to the electromagnetic coupling among the nearby transmission lines,grounding fault occurred in one of the polar conductors may affect another polar conductor and the circuits nearby on the some tower and bring new problems on steady-state operation of HVDC project.PSCAD/EMTDC is used to establish the model of two bi-polar HVDC power system According to the actual DC transmission engineering system parameters,and the interaction between two ± 500 k V HVDC project erected on the some tower under different faults would be simulated in detail and analyzed in depth.The research items include: The influence of the fault HVDC system on the other HVDC system that involved in double HVDC system erected on the some tower,as a fault occur at the AC system of the first HVDC system;The electromagnetic coupling among the nearby transmission lines when unexpected touch between one polar conductor and the other polar conductor(unlike polar belong to the same circuit or like polar on the nearby circuit)occur;The influence of fault pole on the health one,The recovery of health system and the transient overvoltage in healthy system when 0.4s or0.8s metallic grounding fault occurs at the beginning,mid-point and ending terminal in monopole line and bi-pole(like polar and unlike polar)line and tri-pole line respectively;What's more,the differences between conventional HVDC system and double HVDC system erected on the some tower are compared while the fault occurs at the beginning,mid-point and ending terminal in monopole line,as well as the faults that occur at the AC system of HVDC.A comparative analysis of electromagnetic coupling about fault lines under different tower model also included.In this paper,the key factors affecting the coupling characteristics under the fault of HVDC transmission system are found through simulation analysis,which provides support for subsequent theoretical research and engineering application.