Numerical Simulation Study On Galloping Of Conductors In500kV Transmission Tower-line System

The galloping of an electrical transmission line is characterized by large amplitude,low frequency, self-excited oscillation, which is occurred under action of continuouswind forces. The tension of conductor may significantly increase by large amplitudeduring galloping. It may bring some huge damage such as rupture of conductor anddamage of tower or even collapse of the tower. Meanwhile, due to the change of tension,the dynamic load of the insulator string also increases exponentially, which would dogreat damage to the connection fittings, pensile fittings and insulator strings, and itseriously affect the operation of transmission lines. Therefore, it has great theoreticaland practical significance of the studies on the galloping characteristic of iced bundleconductors in a transmission tower-line system.Firstly, the influence laws on galloping of iced quad bundle conductor of continuousspans under different wind speed, different span lengths and different span numbers areinvestigated by the presented numerical simulation method for galloping of icedconductor. The results show that the natural frequency of iced quad bundle conductor ofcontinuous spans is lower than that of single span and the galloping frequency isobviously different from that of single span; With the increase of wind speed, thenumber of half-waves of two sides increased and the change of middle span is verysmall; The difference of galloping mode decreases with the increase of span numbersand large span is more complex; The galloping mode of iced conductor of continuousspans is obviously different from that of single span. Therefore, we should considerthese differences when the anti-galloping of iced bundle conductor is researched.Sub-span vibration is obvious during the galloping of iced conductor in continuousspans when the wind speed is larger.The numerical simulation method of galloping of iced conductor in transmissiontower-line system is investigated by ABAQUS software. The finite element models ofisolated transmission tower-line systems are set up, which include strain towers, bundleconductors, ground wires, spacers and insulator strings. And the galloping processesunder different wind speed and span lengths are numerically simulated. The resultsshow that galloping traces and vibration amplitude of conductors in different span anddifferent phase are different; The galloping frequencies calculated from tower-linesystems and line systems are basic agreement; The vertical vibration amplitudes obtained from tower-line systems are similar with those obtained from line systems, butthe horizontal vibration amplitudes obtained from tower-line systems are significantlygreater than those obtained from line systems; The change of stress on tower is obviousduring galloping. The max stresses of some bars exceed the allowable stress of materialunder some certain wind speed, which may cause the damage of towers.According to the continuous transmission line sections, the finite element models ofcontinuous transmission tower-line systems are set up and the processes of galloping arenumerically simulated. The results show that the characters of galloping with each spanand phase in tower-line systems are basic agree with those calculated from thecontinuous span systems; In general the stress of conductors and tangent towers duringgalloping under various wind speed and span length is smaller, which far less than theallowable stress of materials. So the rupture of conductor and damage of tangent towerduring galloping may cause by fatigue failure.The vibration amplitudes and stresses of conductors during galloping calculatedfrom the isolated and continuous tower-line systems are analyzed. Through thecomparative analysis with the existing simplified theoretical formula and empiricalformulas, it is found that the simplified formula presented by Hunt and Richards issuitable for galloping amplitude estimation of dead-end span; the empirical formulapresented by Lilien and Havard is suitable for galloping amplitude estimation ofsuspension span, and the simplified formula by Baenziger is suitable for dynamictension estimation of conductors in both dead-end and suspension spans. According tothe results of numerical simulation, the formulas were modified on the base of theexisting formula.The results of this study provide important theory bases for the study ofanti-galloping technology in transmission tower-line systems. And it has a certainreference value to consider the design of tower and the safety assessment of duringgalloping.