System Transient Analysis Research Articles

Exploring the power of wavelet analysis

Wavelets are a recently developed mathematical tool for signal analysis. Informally, a wavelet is a short-term duration wave. Wavelets are used as a kernel function in an integral transform, much in the same way that sines and cosines are used in Fourier analysis or the Walsh functions in Walsh analysis. To date, the primary application of wavelets has been in the areas of signal processing, image compression, subband coding, medical imaging, data compression, seismic studies, denoising data, computer vision and sound synthesis. Here, the authors describe how wavelets may be used in the analysis of power system transients using computer implementation.

An inherent parallel algorithm for analyzing power system transient characteristics on a multiprocessor system

This paper will present an inherent parallel algorithm for power system transient analysis with detailed generator stator and network transients taken into account. The component connection model (CCM) will be applied to the modeling and assembling of the power system components for developing an integrated system representation, in which the state equations of system components can be handled separately. The waveform relaxation method (WRM) will then be used to solve those separated component equation sets concurrently. This combined algorithm is thus suitable for parallel processing, and the remarkable speed-up effect of this algorithm by the concurrent and vectorized numerical realizations on an Alliant FX/80 multiprocessor system will be provided for illustration.

Dynamic model of a three-phase power transformer

An adequate mathematical model of a three-phase power transformer is one of the important elements in the programs for the computer analysis of power system transients. Featured in this paper is the simulation model of a three-phase, three-limb core-type power transformer. Nonlinear effects of saturation, hysteresis and eddy currents are considered. Two ways of creating major and minor hysteresis loops are presented. The transformer model, described by a system of time dependent differential equations, is solved by an efficient numerical algorithm. The behaviour of the transformer model during switching-in and fault transients, as well as other types of transients, has been tested. The computed transient waveforms are compared with the measured ones and there exists very close agreement between them.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Countercurrent Flow Limitation Model for RELAP5/MOD3

A countercurrent flow limitation model is incorporated into the RELAP5/MOD3 system transient analysis code. The model is based on the form used by Bankoff et al., and it is implemented in a manner similar to the RELAP5 choking model. Simulations using Dukler and Smith’s air/water flooding test problem demonstrate the ability of the code to significantly improve its comparison to data when a flooding correlation suggested in Dukler and Smith’s study is used.

A frequency-domain Z-bus algorithm utilizing symmetrical components for transient analysis during capacitor switching

Abstract This paper presents a new method for digital simulation of a transmission, subtransmission or distribution system for transient analysis during capacitor switching. The method is based on the frequency-domain analysis utilizing the symmetrical component principles and the Z-bus impedance matrix in the complex frequency domain. The paper emphasizes the concepts of the method, describes the necessary boundary conditions, explains the pertinent assumptions and shows an example of the simulation on an actual subtransmission system.

Transient analysis for antiproliferative gene activity.

A subset of tumor suppressor genes presumably functions by the inhibition of cellular proliferation; however, antiproliferative activity after transfection with putative suppressor genes has been difficult to demonstrate and often requires lengthy selection either in nude mice or in vitro. A rapid alternative is presented here that utilizes a gene encoding a surface marker protein to identify transfectants in a transient expression assay. In this assay the labeling index, rate of DNA synthesis, cell-cycle distribution, and surface receptor display are measured by flow cytometry. Human beta-interferon, a gene with proven antiproliferative activity, was studied using the transient analysis system. The beta-interferon gene was introduced into human tumor cells along with the marker gene encoding the 55-kDa subunit of the human interleukin 2 receptor. Within a few days of transfection, analysis of transfectants by flow cytometry revealed a decrease in the fraction of cells in G2/M and an increase in the fraction of cells in G1/G0 and S phases. The distortion of the cell cycle was accompanied by as much as a 69% reduction in the rate of DNA synthesis and, in some experiments, an unanticipated increase in the labeling index. Therefore, cells accumulating in S phase were not blocked but continued to synthesize DNA although at a reduced rate. These studies on DNA synthetic rates revealed the caveat that screening for antiproliferative candidate genes with a labeling index alone could, in certain circumstances, exclude potentially interesting sequences from further consideration. Although this transient analysis system was developed for studies on cellular proliferation, it may prove suitable for phenotypic assays on other genes as well.

Assessment of the MHD Capability in the ATHENA Code Using Data from the ALEX Facility

The ATHENA (Advanced Thermal Hydraulic Energy Network Analyzer) code is a system transient analysis code with multi-loop, multi-fluid capabilities, which is available to the fusion community at the National Magnetic Fusion Energy Computing Center (NMFECC). The work reported here assesses the ATHENA magnetohydrodynamic (MHD) pressure drop model for liquid metals flowing through a strong magnetic field. An ATHENA model was developed for two simple geometry, adiabatic test sections used in the Argonne Liquid Metal Experiment (ALEX) at Argonne National Laboratory (ANL). The pressure drops calculated by ATHENA agreed well with the experimental results from the ALEX facility.

A Synthesis Method for One-Port and Multi-Port Equivalent Networks for Analysis of Power System Transients

Equivalent networks can be used in power system simulation to reduce simulation equipment or computer time and memory space. In this paper, an iterative method is developed for synthesizing one-port equivalent networks by the removal of poles corresponding to resonances of the driving-point impedance or admittance function. This results in networks formed by the series or parallel connection of modular RLC circuits. The RLC values are calculated using a parameter-optimization technique. Multi-port equivalent networks are first configured as ? or T forme composed of one-port network branches and the latters are then synthesized by the proposed method for one-port equivalent networks.

A Synthesis Method for One-Port and Multi-Port Equivalent Networks for Analysis of Power System Transients

A Synthesis Method for One-Port and Multi-Port Equivalent Networks for Analysis of Power System Transients

Oconee RETRAN Model Comparisons with Plant Transient Data

This paper discusses an application of the RETRAN-01 code developed by the Electric Power Research Institute which is currently in wide use by the electric utility industry for light water reactor (LWR) system transient thermal-hydraulic analysis. The most attractive qualification method for LWR plant models utilizes direct comparisons with plant transient data. A RETRAN model of the Oconee Nuclear Station (BandW 2568 MW(thermal)) was used to simulate four plant transients. The code demonstrated excellent capability for modeling boundary conditions and control system responses. The close coupling between the primary and secondary systems via the once-through steam generator was successfully simulated.

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Authors

Reduced order modeling for power system transient analysis

With the development of power system interconnection and with the increase of transmitted power, some cases are arising where the capacity of a transmission network is limited by steady-state stability. Analysis of steady-state stability raises some difficulties, which are different in nature from those raised by transient stability analysis. To reduce the computational difficulty associated with steady-state stability analysis, a proposed method derives an equivalent network with a reduced number of generators. In some of these methods a part of the power system is simplified so as to keep invariant the short-circuit capacity at a specific point. Nevertheless, equivalency of the reduced model obtained by these methods has not been discussed in detail theoretically. A method to reduce the number of generators is proposed assuming that the electromotive force behind transient reactance of each generator is constant.

Transient Analysis of Systems with Exponential Transmission Lines

Two computer solutions are given for pulse propagation along exponentially tapered transmission lines with arbitrary nonlinear sending and receiving networks. The solutions allow series and shunt loss terms per unit of length of the line. The method of characteristics is shown to be computationally superior to the cubic spline method in terms of accuracy and efficiency.

Transmission Line Models for Use with Circuit/System Analysis Programs

Techniques for modeling multiconductor transmission lines for use with the SCEPTRE computer program are presented. The transmission line models developed can be modified for compatibility with other circuit/ system transient analysis programs and are amenable to modification to include nuclear weapon effects. The general modeling approach has been to develop computationally efficient and accurate terminal models which can be arbitrarily loaded at the source and load ends and which can be used in conjunction with nonlinear electronic circuit models using either simplified or discrete modeling techniques. The concept of the method is to derive a set of transfer functions in the Laplace domain relating forward and backward traveling waves on the line to voltages and currents at the source and load ends of the line, approximate the transfer functions with a set of orthonormal polynomials, and represent the resulting rational polynomials in the time domain with state variable differential equations. For the multiconductor case, the orthogonal characteristics of wave propagation are used to decouple the modes of propagation except at the source and load boundary condition circuits.

Synchronizing transients and synchronizers for large machines

IT IS a curious fact that the phenomena encountered in synchronizing operations have received scant attention in the technical literature even though the phenomena have been encountered ever since two synchronous machines were first operated in parallel, and even though a large number of synchronizing operations are performed every day. Possibly the explanation is due to two facts; first, that the ideal conditions introduce no disturbance, and, second, that the synchronizing transients are usually not large but for analysis require consideration as a stability problem of considerable complexity. A review of the synchronizing problem has become desirable because of the development of new types of automatic synchronizers and because of the progress in the analysis of system transients in connection with system stability. This study includes only those synchronizing operations for which the voltage, phase, and frequency conditions are matched before the connection is made; it does not include self-synchronizing methods.