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.
The Short Circuit Electromagnetic Force of the Three-Phase Encapsulated Gas Insulated Bus-Bar
This paper discribes various optimum design conditions for a three-phase encapsulated gas insulated bus-bar (3 phase GIB) on the basis of the results of the quantitative analysis and the experiments with respect to the short circuit electromagnetic force. It reveals that the characteristics of the short circuit oscillation in 3 phase GIB are notably different from those in single phase bus-bars. The experiments showed that the fundamental mode oscillation of conductors was dominant with strong attenuation of 10 ~ 12%. The effect of enclosure current should also be taken into account in case of aluminuim enclosure.
Vibration of a string with attached concentrated masses
Abstract The free and forced vibration of a string with a concentrated mass attached at the middle is formulated and solved with the aid of the Dirac δ-function. The method developed is extended to the case where many masses are attached to the string. Compactness in presentation and manipulation is achieved by this new method.