A Contribution to the Frequency Analysis and Transient Response of Power Transformer Windings

Abstract—This article proposes a new approach to study the frequency response and the transient analysis of power transformer windings. For improved accuracy, the suggested model includes, among other equivalent circuit elements, the mutual magnetic couplings between any winding turn and all others. This implies that the equivalent inductance of any considered turn will be a location-dependent parameter. Accordingly, the winding will be analyzed as a non-uniform transmission line. Through the application of a recursive circuit reduction technique, a closed-form Laplace s-domain analytical expression for the winding's input impedance can be obtained for any neutral treatment. The resulting expression can be used to determine the winding's series and parallel resonance frequencies. The s-domain expression for the input impedance, in connection with the numerical inverse Laplace transform, will be utilized for determination of the winding's time-domain transient response for any input voltage or current time waveform. Accuracy increases with the assumed number of winding sections, which can be even increased to the actual number of turns, limited only by the available computation resources. The results of case studies are in good agreement with those available in the literature using the time-domain solution of the simultaneous differential equations in the state variables.     

Design of a soft-error robust microprocessor

The costs to protect a commercial microprocessor against soft errors are discussed in this work. Based on hardware and time redundancies, a protection scheme was designed at RT level to mitigate transient faults on combinational and memory circuits. A fault-tolerant IC version of a mass-produced 8-bit microprocessor is protected by the scheme. Design issues and results in area, performance and power are presented comparing the robust microprocessor with its non-protected version. The costs by flip-flop are also discussed permitting to estimate the overheads in area for any architecture. Furthermore, the RT-level protection scheme is compared with an electrical-level scheme based on a non-standard gate.     

LATTICE BOLTZMANN SCHEME TO SIMULATE TWO-DIMENSIONAL FLUID TRANSIENTS

ＮＯＭＥＮＣＬＡＴＵＲＥｐα ———ｐｒｅｓｓｕｒｅｄｉｓｔｒｉｂｕｔｉｏｎｆｕｎｃｔｉｏｎｐ(0 )α ———ｅｑｕｉｌｉｂｒｉｕｍｄｉｓｔｒｉｂｕｔｉｏｎｆｕｎｃｔｉｏｎｅα———ｌｏｃａｌｐａｒｔｉｃｌｅｓｔｒｅａｍｖｅｌｏｃｉｔｙｒ———ｌｏｃａｔｉｏｎｏｆｃｏｍｐｕｔａｔｉｏｎａｌｇｒｉｄｎｏｄｅδｔ ———ｔｉｍｅｉｎｃｒｅｍｅｎｔτ———ｔｈｅＢＧＫｒｅｌａｘａｔｉｏｎｐａｒａｍｅｔｅｒα———ｉｎｄｅｘｏｆｐａｒｔｉｃｌｅｓｔｒｅａｍｄｉｒｅｃｔｉｏｎｂ———ｔｈｅｎｕｍｂｅｒｏｆｐａ…     

Aliasing probability transients

Test data reduction for digital systems is often accomplished through the use of a feedback shift register. This method, known as signature analysis, can exhibit error masking or aliasing. Recent analysis has shown that the use of a primitive polynomial for the register feedback can reduce the probability of aliasing. In this work we demonstrate that not all primitive polynomials are created equal. Some primitive polynomials can have very large transients in their aliasing probability. For example, 1 +X ¹³ +X ³³ can exhibit an aliasing probability more than a million times larger than its asymptotic value of 2^–33. An evaluation procedure is presented which can identify polynomials with good transient characteristics. Some recommended feedback polynomials are given.     

Thermal restoration of a wall after the interruption of solar radiation flux

The transient phenomenon of the thermal restoration of an opaque wall of a room after the interruption of solar radiation flux was analysed. The wall, was initially, in thermal equilibrium under solar radiation. When the solar radiation flux was interrupted, the temperature distribution on the wall cross-section went through a transient state until it reached a final equilibrium state. During the thermal restoration of the wall, a thermal gain is maintained for the room as a result of the exploitation of a part of the thermal energy stored in the wall. Analytical expressions have been obtained for the duration of the thermal restoration, for the thermal gain of the room during this transient state and for the coefficients of storage and exploitation of the solar radiation by the wall.     

弱约束管道系统水锤研究与进展

充液管道中瞬变流的研究有着悠久的历史，积累了极为丰富的文献和资料。人们对系统不稳定流的认识也随着科学技术的进步不断发展开拓，内容及航空航天，石油化工，机械传动，水利电力等２０多个研究方向。     

Shunt capacitor placement in radial distribution networks considering switching transients decision making approach

This paper provides a new approach in decision making process for shunt capacitor placement in distribution networks. The main core of the evaluation process is a multi-objective framework to allocate the capacitor banks. The power loss and the total harmonic distortion (THD) are the objective functions of the system under study in a long-term planning horizon. In order to select the executive plan introduced by using a multi-objective model, transient switching overvoltages have been considered. As the size and location of shunt capacitors may result in unacceptable overvoltages, the proposed technical decision making framework can be applied to avoid corresponding damages. In this paper, an iterative conventional power flow technique is introduced. This technique can be applied to evaluate THD for distribution networks as well as other power flow based objectives, such as power losses calculation and voltage stability assessment. The presented framework is a two stage one where at the first stage, a non-dominated sorting genetic algorithm (NSGA-II) augmented with a local search technique is used in order to solve the addressed multi-objective optimization problem. Then, at the second stage, a decision making support technique is applied to determine the best solution from the obtained Pareto front. In order to evaluate the effectiveness of the proposed method, two benchmarks are addressed in this paper. The first test system is a 9-bus distribution network and the second one is an 85-bus large scale distribution network. The simulation results show that the presented method is satisfactory and consistent with the expectation.     

49-2游泳池式反应堆超设计基准事故的筛选与分析

为保证49-2游泳池式反应堆在超寿期下的安全运行,需进行超设计基准事故分析。由于难以采用概率安全评价(PSA)方法进行分析,所以本文无条件假设最严重事故来得到一保守结果。主要分析了全厂断电下未能紧急停堆的预期瞬变(ATWS)、水平孔道断裂和停堆后堆芯完全裸露的事故,以及应急能力。结果表明:在全厂断电ATWS下堆芯是安全的;水平孔道断裂及其他因素造成失水时,只要2.5h内堆芯不裸露即可保证燃料元件不熔化;非能动破坏虹吸能力和多样的应急补水方式能保证堆芯不裸露。     

机组转动惯量GD2的取值及对水电站过渡过程的影响

论述了水轮发电机组转动惯量的初步计算方法，说明转动惯量的优化应该结合导叶关闭规律优化及其他优化措施一起完成。通过对水电站过渡过程中机组转动惯量与转速上升率和调节时间的敏感性分析，发现转动惯量存在临界点，并且后者的临界值小于前者，验证了导叶关闭规律优化中尽量用足机组转速上升率的合理性。