| Along with the upgrade of the power grid and the development of the distributed generation,power cable has been widely used because it can beautify the city's appearance and optimize the distributed layout.There are more and more hybrid lines on the basis of the original overhead line.Therefore the research of fault protection and location in hybrid multi-terminal HVDC systems has very important practical significance for ensuring the safe and stable operation of power system.In this paper,the influence of the inductance terminal on the transient characteristics of the traveling wave is studied,and a protection scheme for multi-terminal system based on this characteristic is proposed.This method uses the difference of transient energy between the internal and external voltage waves as the basis for fault protection,and can identify the fault quickly and reliable.The simulation analysis shows that this method is not affected by fault type,fault distance and transition resistance,and can identify the internal and external fault accurately even when the case of high resistance fault in the internal remote area and the double-pole fault in the external bus.This paper also analyzes the characteristics of traveling wave between overhead lines and cable.In order to avoid the complex features of traveling wave processing in the multi-terminal hybrid line,a novel algorithm based on the double-terminal traveling wave method is proposed.This algorithm uses the arrival time of the initial traveling wave can select the fault line and locate the fault.Corresponding simulation cases were carried out to verify the adaptability and the high accuracy in different situation of the proposed algorithm.The research content of the paper has the practical significance for fault protection and location,which can provide the theoretical basis for constructing a quick and reliable fault protection system in hybrid multi-terminal HVDC systems. |
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