GALLOPING OF BUNDLE CONDUCTOR

A useful design tool is developed for a bundle conductor of an electrical transmission line by using a three-degree-of-freedom hybrid model. The model is adaptable because it incorporates numerical mode shapes determined by numerically employing the finite element technique to form relevant matrices. On the other hand, it is quite computationally efficient because analytical expressions are used to investigate the initiation and steady state amplitudes of galloping. The model accommodates interactions of the vertical, horizontal and torsional movements, non-linear aerodynamic loads, a non-uniform ice geometry, distributed and discrete galloping control devices, and a variation of the wind along a span. By neglecting the sub-span motions between the conductors, a bundle is modelled as an equivalent single conductor so that the initiation conditions for galloping, periodic and quasi-periodic states and their stability conditions are considered by taking advantage of previous achievements for a single conductor. Numerical examples are presented to assess the accuracy of the results obtained from the model in comparison with analogous data from a more sophisticated finite element analysis. Parametric studies are reported for limit cycle amplitudes with variations of the critical wind speed, wind speed above the critical wind speed, static tension and span length.