| Submarine cables act as lifelines in the transmission of electricity between inland,island and offshore drilling platforms.In recent years,there have been more and more offshore wind power platforms and offshore oil drilling platforms.Submarine cables have been used in large quantities,and the incidence of submarine cables fault has been increasing.Due to the complex and variable environment of submarine cables,it is necessary to perform fault diagnosis when fault occurs,include fault signal detection and fault location.And use professional cable salvage vessels and professionals to accurately locate,salvage,inspect and repair and re-lay.The fault phase selection can be completed by measuring the insulation resistance.Long fault repair time and large economic loss.Therefore,it is very important to improve the accuracy of submarine cable fault location and shorten the repair time.Short circuit faults are the main fault types.By consulting relevant data,it is found that the submarine cable fault can be studied from two aspects.First,analyzing the current and voltage physical characteristics caused by the submarine cable fault in the early stage,and strengthened maintenance in the submarine cable with insulation degradation;second,research on the method of location and improve the accuracy of submarine cable short circuits fault location.The following works were be taken by this article:Firstly,introducing the analysis of the composition of submarine cables and summarizing the causes and types of aging of submarine cable insulation.The variation of the shape of the electric branch caused by the insulation aging of the submarine cable with voltage and the rectification effect of the water branch are analyzed.The fault voltage and fault current characteristics of single-phase short-circuit faults of submarine cables caused by insulation degradation are analyzed by Simulink simulation.Secondly,based on the theory of arc,the early fault model of submarine cable was built,and the fault current,fault voltage and fault resistance characteristics caused by fault arc are analyzed by the principle of energy balance.Based on the mathematical derivation formula of energy balance principle,by changing the physical parameters of the submarine cable fault arc module to analyze and summarize the trend of the peak and incremental changes of the early short-circuit fault current and the differences between the characteristics of each operating state.Summarizing the effects and key factors of early short-circuit faults.Again,because of the source of the interference noise of the signal during the detectionprocess is complex,it is analyzed based on statistical characteristics.Add random interference noise,Gaussian distribution noise,Rayleigh distribution noise and Exponential distribution noise to the early failure module of submarine cable,and pass moving Average filtering,Median filtering,Wiener filtering,Traditional LMS adaptive filtering,S-function variable step size LMS and Improved LMS algorithm,and compares the convergence speed and average mean square error of each algorithm in the simulation experiment.The results show that Improved LMS adaptive filtering algorithm has better filtering effect.Finally,the superiority and inferiority of single-ended and double-ended methods in traveling wave ranging theory are analyzed and compared.The single-ended ranging method in traveling wave fault location is selected,but the single-end method has the effect of traveling wave-folding reflection.Therefore,the wavelet recognition of the db4 wavelet of the wavelet transform is proposed.The 35 kv cross-linked polyethylene submarine cable fault location model is built in MATLAB/Simulink.And to extract the fault traveling wave head information by wavelet transform and calculate the modulus maximum.The single-ended fault location error based on wavelet transform is verified under different fault distances and fault types.The measurement results show that the method has higher measurement accuracy. |
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