Research On Wear Characteristics Of Overhead Line Of Electrified Railway In Aeolian Vibration

Overhead line is the important carrier to transmit power for the electrifiedrailway and an important part to ensure the safety operation of the railway system.With the rapid development of the electrified railway and the improvement of thetransmission voltage levels, how to reduce the line loss is a hot research area incurrent study. Because most line loss is caused by the wire wear, and the aeolianvibration is the main factor to cause the aeolian vibration, it is of great significance toresearch the wire wear characteristic in aeolian vibration in improving the reliabilityof the transmission line and reducing the line loss.This research is supported by the National Natural Science Fund project. In thispaper, the LGJ150/25aluminum conductor steel reinforced (ACSR) which often usedin the35kV overhead transmission lines is taken as research object. The aeolianvibration of line under various conditions was simulated, and the wear characteristicsand the corona loss characteristics of the worn wires were researched. The maincontents of this thesis are as follows:(1)The contact finite element model of the whole overhead line was establishedby analyzing the overhead line with statics and contact mechanics. The contact stressdistributions of the layers of the aluminum wire strands under static tensions wereanalyzed, and the changing rules of the contact stress of wire strands have beenconcluded. By simulating the aeolian vibration with loading the sinusoidal excitationon the finite element model of the overhead line, the contact stress distribution lawamong the inside strands of the line under the aeolian vibration condition wasrevealed, and the impact of the vibration frequency on the stress distribution ofstrands and the micro-displacement have been analyzed.(2)The overhead lines aeolian vibration simulation test-bed was established. Andthe wear simulation tests of the overhead lines have been finished under differentvibration frequency, vibration cycles, loads and atmospheric and other parametersconditions. By orthogonal experimental design, the effects of experimentalparameters on fretting wear of the wire were analyzed, and the results show that, theintensity of electric current and atmospheric environmental impact on the fretting wear of the wire was the largest, the pretension is the second and the influence ofvibration frequency is relatively small. Meanwhile the influence rules of the current,the pretension, the vibration frequency and the atmosphere on the wear of conductorsare revealed. By the controlling the parameters variation tests, a relation model of theaxis direction location of the test conductor and the wear area was built, and thelocation of the most wear on test conductor could be found. Took the wires in middlelocal and the exit local of the middle clip, for example, the relation models of theinfluencing factors and the wear areas were built. The analysis results of the modelsare the same basically with the orthogonal experimental, and the models can providethe relevant data for the further research about the conductor wear character.(3) Morphology characteristics and composition of the worn wires and theserviced wires were observed by JMS-7500F Cold field emission scanning electronmicroscope (SEM) and X-ray (EDS)，and the result revealed the influence mechanismof current and voltage on the contact characteristic between inner and outeraluminium wires and between the steel core and inner aluminium, which showedthofat the change of the current had more sensitive influence on the conductor wear.By observing the surface morphology and composition of the conductors which weretested under different current and different corrosion medium condition, the influencelaw of different corrosion medium on the wire wear has been analyzed, and theanalysis results reveal the contact wear mechanism of the current-carrying wire undersome kinds of conditions, which is basically in accord with the working wires.(4) The influence of the size, shape and distribution of the wear particles on thecorona discharge of the wire was researched by the finite element simulation, and theresults of the corona test of the weared conductors were analyzed. The simulationresults show that the wear particle attached to the surface of the wire will lower theoriginal corona onset voltage and the different sizes of the wear particle (especiallythe different height) and different intensity influence the corona discharge in differentdegree. A system was established to test the wire corona characteristic, and CoroCAMIV+ultraviolet imager was used to measure the discharge photos number of the wornwires at different loaded voltages. Tangent method was used to determine the wear ofthe wire corona onset voltage. The influence of the different parameters, such asvibration cycle number, pretension, frequency, atmospheric environment and loaded voltages, on the corona discharge was researched. By comparing the relationship ofthe corona onset voltage at each position of the single wire and the correspondingwear mass loss, it was known that there was no linear relationship but a link betweenthe corona onset voltage and the wear mass loss at each point of the wire. The changetrend of the corona onset voltage is basic contrary to the wear mass loss. The studyfind that the corona onset voltage at the same position of the wires which workeddifferent cycle times decrease with wear mass loss increasing.