Research On Fault Identification And Location Method Of Hydropower Station Transmission System

China's hydropower industry is developing very rapidly,but hydropower stations are generally built in the deep mountain valleys where the terrain is dangerous.Therefore,transmission lines have always occupied an extremely important position in China's power system.Most of the transmission line failures are caused by lightning strikes.Effective identification of lightning strikes and fault types is a prerequisite for fault location of transmission lines using the traveling wave method.Traveling wave ranging method is widely used in fault location of transmission lines,but the accuracy of its ranging results needs to be improved.This paper mainly studies the lightning strike identification method of transmission line,the method of traveling wave head detection and the traveling wave ranging algorithm.In order to solve the problem that lightning strikes and lightning strikes can not quickly and accurately identify the types of lightning strikes and make effective defense measures,this paper proposes an improved comprehensive lightning strike type identification method.Firstly,the method of constructing the integral criterion based on the monotonicity and symmetry of the lightning transient voltage signal waveform is used to identify the non-fault and fault lightning strikes.Then,the high and low frequency energy ratio criterion is constructed based on the distribution characteristics of the energy characteristic values of the transient voltage signal.,identify non-lightning strikes,lightning strikes and short-circuit faults.In order to solve the problem of marginal effect and modal aliasing of the original signal layering by the Empirical Mode Decomposition(EMD)in the Hilbert-Huang Transform(HHT).In this paper,the modified HHT algorithm is proposed by combining Variational Mode Decomposition(VMD)with Hilbert Huang transform.Finally,the effectiveness of the improved HHT algorithm is verified by PSCAD simulation.In order to solve the problem of inaccurate fault location caused by insufficient or excessive decomposition of fault traveling wave signal in the process of variational mode decomposition,this paper proposes a traveling wave fault location method with parameter alternately optimized VMD.Firstly,the method of alternately optimizing the VMD by parameters is used to obtain a more reasonable k value and ? value.Secondly,according to the Teager Energy Operator(TEO),the single component signal has the advantages of fast demodulation speed and high precision.The improved VMD and TEO are applied to the fault traveling wave detection of the transmission line,and the effectiveness of the detection method is verified by simulation.In order to solve the influence of factors such as traveling wave velocity and sag during fault location,this paper deduces a new algorithm for traveling-line ranging of double-ended faults on transmission lines that is not affected by wave velocity and line sag and fault location.The PSCAD simulation shows that the positioning method is correct,the calculation is simple,and the positioning accuracy is high.