Influence of Short-Circuit Duration on Dynamic Stresses in Substations
The short-circuit peak current and the electromagnetic short-circuit peak force appear at about 10 ms after the short-circuit inception. However, the maximum value of dynamic stress due to the electromagnetic forces may occur much later and depends on the fundamental frequency of the structure. A decrease in dynamic stress can be obtained even if the short-circuit duration is much longer than 10 ms. In the presentwork, the dynamic stress on stiff conductors and insulators during the short-circuit, as well as, the subsequent free oscillation after fault clearing, are analytically determined and the influence of short-circuit duration on the dynamic stress in certain cases of busbar structures is investigated. Furthermore, the shortest short-circuit durationwhichresults in maximum dynamic stress is given for the entire range of the relevant mechanical fundamental frequencies.
Response of Bus Bars on Elastic Supports Subjected to a Suddenly Applied Force
The dynamic response of a bus bar subjected to a suddenly applied fault current has been determined by means of a mathematical model. The theoretical response was in good agreement with experimental results obtained with a small-scale bus-bar model. This theoretical technique permits the dynamic response of any bus-bar system to be predicted for any fault current.
Mechanical stresses in busbar supports during short circuits
THE design of busbar layouts calls for the determination of the stresses occurring in the bus supports during short circuits, because the stresses in question may become sufficiently large to weaken, or even rupture, the supports. Moreover, an understanding of the factors affecting the stresses will often permit the designer to modify the layout so as to reduce the stresses, and thus save material or prevent failure. Hence investigations have been directed towards the calculation of support stresses due to electromagnetic forces caused by short-circuit currents in busbar structures.