The Research Of Traveling Wave Fault Location Method For Submarine Cable-Overhead Line Hybrid Lines

With the rapid development of modern industry,the techniques have been improved continually such as development of marine resources,transmission power to offshore drilling platform and the interconnection of regional power grid across the strait.It makes the submarine cable-overhead line hybrid transmission line develop rapidly.But the traveling wave fault location method which is suitable for uniform transmission line is not applicable to the three section submarine cable-overhead hybrid line-transmission line.At present,there are few traveling wave fault location methods for the three section submarine cable-overhead line hybrid transmission lines.The two terminal fault location method is commonly applied for the two-section hybrid transmission line.However,the two terminal traveling wave fault location method is affected by the line length and the time synchronization error,and it will lead to inaccurate ranging results.Therefore,the transmission characteristics of fault traveling wave in submarine cable-overhead line hybrid line has been studied deeply in this paper.And a distance ranging method of traveling wave has been proposed for three section hybrid transmission lines.The main work of this paper is as follows:(1)The propagation characteristics of fault traveling wave on the line are analyzed theoretically,and we analyze the refraction and reflection characteristics of fault traveling wave at the connection point of the submarine cable-overhead hybrid transmission lines.The polarity and amplitude characteristics of the voltage and current traveling wave at the connection point has been deeply studied.(2)According to submarine cable-overhead line hybrid transmission lines,it proposes the piecewise distance ranging of traveling wave fault location method,which suits any structure hybrid transmission line.First,according to the time difference of the initial traveling wave arrival between the two distance measuring equipment on the two ends,it calculates the possible fault distance when the fault is at the end of the line.Then,it searches the line from the back to front according to the possible fault distance.The fault section is judged out and the preliminary fault location is given out at the same time.Finally,according to the principle of the single terminal fault location method,we calculate the accurate ranging results.(3)According to submarine cable-overhead line hybrid transmission lines,it proposes the global distance searching method of traveling wave fault location method,which suits any structure hybrid transmission line.First,according to the time difference of the initial traveling wave arrival between the two distance measuring equipment on the two ends,it calculate the possible distance when the fault occurs at each section of line.Then the fault section is judged out and the preliminary fault location is given out.Finally,according to the principle of single terminal fault location method,we get the accurate ranging results.(4)According to submarine cable-overhead line hybrid transmission lines,it proposes the distance ranging of traveling wave fault location method of hybrid transmission line,which is based on multi-terminal information.First,according to the time difference of the initial traveling wave arrival between the two distance measuring equipment,which is on the end of each uniform section transmission line,it calculates the possible distance when the fault occurs at each section of line.Then the fault section is judged out and the preliminary fault location is given out.Finally,according to the principle of single terminal fault location method we get the accurate ranging results.(5)Simulation models have been built by PSCAD,and MATLAB is used to verify the above proposed methods.Different faults have been set to verify the feasibility of the proposed methods.The proposed new methods called distance ranging method of traveling wave are applicable for the submarine cable-overhead line hybrid line.In these methods,ranging results are given by the single terminal ranging principle which has the high reliability.When there is a fault at the submarine cable-overhead line hybrid transmission line,the fault location can be located quickly and accurately by using these methods.It has good engineering application value.