Research On Traveling Wave Protection Of High Voltage Direct Current Transmission Lines

HVDC(High Voltage Direct Current)transmission takes an increasingly important position in the long distance and high-power transmission project,for its large power of transmission,low cost and good performance advantages of control.It is regarded as the principal means of high-capacity,long-distance transmission and asynchronous networking in developed countries.In China,HVDC transmission become the hot spot of the electric power construction of our country because of the power of west to east,north and south for the national network.With HVDC transmission play a more and more importance role in power grid,how to enhance the security and reliability of the system has become a emergency problem to solve,so it is necessary to make a simulation study of the protection and control mode characteristics of HVDC transmission system,analyzes the fault characteristic and improve protection scheme further.This article first introduced the general situation of HVDC transmission project,the composition of DC transmission system and the characteristics of DC line.Based on the analysis of the process of DC line fault,the concept of travelling wave was introduced,and the principle of traveling wave protection was further elaborated.And then the paper builts a simulation model of the bipolar 12 pulse HVDC system on the basis of GezhoubaShanghai Bridge DC Transmission System by using the simulation software PSCAD/EMTDC.Aiming at the development trend and status quo of line protection at home and abroad,the principle of traveling wave protection based on transient fault components is analyzed.The principle of traveling wave protection criterion for HVDC transmission lines with polar-wave traveling wave and voltage traveling wave is studied and compared,and the protection scheme is compared.The performance,and its application was discussed in depth.The results show that these two protection scheme have a degree of lack of vulnerability to noise interference.To that end,this paper introduces and applies the wavelet transform mathematical tool to the HVDC lines protection,which forms the distance protection and direction protection of current polarity comparative based on wavelet transform for HVDC lines.Having been taken full simulation analysis in detail,these two kinds of protection principle performance feasibility in practice.Finally,this will provide a theoretical basis and technical support for the protection of HVDC transmission line.Finally,with the current existing high-voltage DC line traveling wave protection scheme,a specific line protection configuration is proposed.The primary protection of traveling wave protection is combined with differential under-voltage protection and line differential protection and simulated by the PSCAD/EMTDC software in the HVDC transmission model,then the scheme is simulation analysised and verificationed.At the end of the paper the results towards these research mentioned above are concluded and the direction of further work is pointed out.