Investigation On Aerodynamic Characteristics And Sub-span Galloping Of Bundle Conductors

Quad bundle conductor and eight bundle conductor are commonly used in UHVtransmission line. Because of the influence of wake interference between bundleconductors, the drag force on leeward sub-conductors will decrease, and lift force willoccur, so that the aerodynamic forces acting on each sub conductor are different.Because of the difference of drag force, it will cause the difference of wind pressurecoefficient; and the lift force will lead to the wake galloping, that is sub-span gallopingof bundle conductors. Meanwhile, there has sub-span galloping in galloping of icedconductors. These are urgent problems to ensure the safty in operation of transmissionline.Firstly, the wind tunnel test of aerodynamic coefficients of measurement for quadbundle conductor and eight bundle conductor was designed. Then, the staticaerodynamic coefficients like lift, drag and moment of each sub-conductor of quadbundle conductor and eight bundle conductor varying with attack angle were obtainedin wind tunnel. It is observed that the wake interference around sub-conductors on thedrag coefficients is obviously dropped; meanwhile it will be affected by lift force. Themoment acting on bare conductor is very small.Comparing with quad bundle conductor;the aerodynamic coefficients of eight bundle conductor varying with attack angle weremore complicated.In order to investigate the galloping of bundle conductors, the wind tunnel testproject of aerodynamic coefficients of measurement for quad bundle conductor andeight bundle conductor was designed. The static aerodynamic coefficients like lift, dragand moment of each sub-conductor of iced bundle conductor varying with attack angle,in the cases of different wind speeds and ice thickness, were obtained in wind tunnel. Itis observed that the wake interference around sub-conductors on the drag and liftcoefficients is obvious, the moment coefficient is less affected, the curves ofaerodynamic coefficients is nearly the same in the case of different wind speeds.Meanwhile, the effect of ice thickness on aerodynamic coefficients is obvious.Air flow around quad bundled conductor, six bundled conductor and eight bundledconductor at typical attack angles were determined by means of using the computationalfluid dynamics software FLUENT. Meanwhile, the drag coefficients are obtained bynumerical simulation method and the results are consistent with those by the wind tunnel test. Compared with the determination method of wind load on conductor incurrent Chinese code and the IEC code for the design of transmission line, the dragcoefficients defined in the Chinese code, and give suggestion for improving the value ofwind pressure coefficient of bundle conductors in design specification.Fluid flow around typical iced quad bundle conductor and iced eight bundleconductor is simulated in numerical method, and the aerodynamic coefficients varyingwith wind attack angle of the conductor are numerically investigated by means ofFLUENT software. Meanwhile, the coefficients are obtained by numerical simulationmethod and the results are consistent with those by the wind tunnel test. The DenHartog and Nigol coefficients determined by numerical simulation are agreed with thoseobtained by the wind tunnel test, which demonstrates that the availability applying thenumerical simulation method to obtain the aerodynamic coefficients of iced conductorsfor analysis of galloping of transmission lines.The numerical simulation method of wake galloping of conductor is investigated byfinite soft ABAQUS. The wake galloping of iced quad bundle conductor, eight bundleconductor and sub-span galloping caused by galloping were numerically analyzed bynumerical method. The wake galloping of quad bundle conductor and eight bundleconductor with different span lengths, wind speeds and spacer arrangement weresimulated. The results suggest, besides sub-span galloping, whole span galloping mayalso occur during wake galloping of quad bundle conductor. Amplitude of quad bundleconductor with non-equidistant spacer arrangement is greater than that quad bundleconductor with equidistant spacer arrangement. The wind speed is higher, to stabilizethe galloping required vibration state time is shorter, it is more easily excited wakegalloping. During wake galloping, the vibration amplitude and the tension of each subconductor of quad bundle conductor is different, and the motion direction of each subconductors may be different, cause "whip" phenomenon. The main mode of wakegalloping of eight bundle conductor is sub-span galloping; amplitude of eight bundleconductor with equidistant spacer arrangement is greater than that eight bundleconductor with non-equidistant spacer arrangement. The wind speed is higher, the moreeasily excited wake galloping, and amplitude of wake galloping is greater; the modes ofwake galloping of eight bundle conductor with different span length are different.Meanwhile, the numerical simulation result of galloping of iced quad bundle conductorsuggests, there have typical sub-span galloping during galloping of bundle conductor. The necessary wind tunnel test dates and effective numerical method for windageyaw, wind induced vibration and sub-span galloping problems of UHV transmissionlines produced by research achievements, so as to find the theory bases for anti-vibration method of bundle conductors.