Seismic Analysis Of The Porcelain High-Voltage Equipments System

Firstly, the importance and behaviors of high-voltage electric equipment with bushings in an earthquake are reviewed. The reasons of equipment damage are primarily brittle destroy of bushings as most earthquake data show. Hence, the seismic capability of equipments is just that of the bushings, namely the maximal strain of bushings controls the equipment damage. According to the structural characteristic of equipments a nd t he c ondition o f r unning e quipments, t he factors t hat i nfluence t he seismic capability of equipments would include bushings, flanges jointing bushings, bracket, dampers, cables, and so on. The goal of this paper is to discuss how these factors influence on the equipments.'Vibration table testing of LW11-252/Q SF6 Circuit Breaker Isolated With Lead Alloy Dampers', which is designed according to several codes, such as GB50260, IEEE693-1997, IEC68-3-3, IEC1166 etc., is reviewed into details. T he t esting d ata show that under the designed vibration waves, the Lead Alloy Dampers are well functioning, not only reducing the strain at the ankle of bushing, but limiting significantly the relative displacement and absolute acceleration at the top of bushing.However, b ecause t he d isplacement o f v ibration t able u sed i n t he t est i s 1 imited t o 4cm, the results of the testing could prove only partially the damping effect for ground motions with significant short-period contents. To investigating the damping effect under other types of ground motion, this paper constituted a three dimensional finite element model, in which the flange is simplified as an elastic joint and the dampers are as bar elements. To compare with the results of the testing, acceleration time-histories outputted from table-board of vibration table. It is proved that the three dimensional model is reasonable and can be used in future by comparing the results of calculation with the results of testing.After t hat, a further p roblem i s s tudied o n d amping effect of Lead A lloy Dampers under ground motions with significant long period contents and ground motions with velocity-pulse. For the first condition, the damping effect is not clear as all. For this case, this kind of damper seems not applicable because it doesn't reduce the strain at the ankle of bushing but increases it under some conditions.Cable connection made of flexible c onductors i s o ne o f the m ost i mportant factors influencing the seismic capability of electric equipments. It is not good to limit the seismic analysis without considering the dynamic cable effect. Therefore, the analysis of the whole system by using large distortion finite element is considered here. At first, based on Dastous' tests, the horizontal forces applied at the cable ends are calculated when they are fixed. And then, the effect of cables with two selected spans acting on two types of beam with different sections and different natural frequency is analyzed. It is found that (a) the existence of cable will increase the dynamic response of beams; (b) cutting down the span of cable will reduce the effect generally; (c) different from the traditional points considering that the cable cannot bring compressive stress, there is press stress a little less than tensile stress existing in cable; (d) under the different types of environment, i.e. to same or different beams at the ends of cable, the behavior of beams with higher natural frequency is almost equal, but the behavior of beams with lower natural frequency will be different. In a word, the influence of cable should be considered for analyzing the seismic capability of electric equipments.