chapter 3 - Bentham Science

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Fault Analysis in Power Systems Applications of Spreadsheets in Education The Amazing Power of a Simple Tool 5 4. Transmission lines are represented by their equivalent series reactances. Series resistances and shunt admittances are ignored. 5. Synchronous machines are represented by constant-voltage sources behind subtransient reactances. Armature resistance, pole saliency, and saturation effects are ignored. To illustrate the analysis of symmetrical faults, consider the five-bus power system whose oneline diagram is shown in Fig. (1.1). Machine, transformer, and line data are given in Table 1.1. The data are given in per unit (p.u.) of a common base. Eg1 Generator 1 Transformer 1 jX" d 1 jXT1 j 0.04 j 0.025 1 jX25 j 0.1 jX45 j 0.05 5 4 2 Transmission lines j 0.125 jX24 Transformer 2 Generator 2 jXT2 jX" d 2 j 0.02 Fig. (1.1): One-line diagram of power system for symmetrical fault analysis. Table 1.1: Synchronous machine, transformer, and transmission line data Generator Bus Subtransient reactance, X ′′ d (p.u.) 1 0.04 3 0.02 Transformer Bus-to-Bus Leakage reactance, XT (p.u.) 1–5 0.025 3–4 0.02 Line Bus-to-Bus Series reactance, XL (p.u.) 2–4 0.125 2–5 0.1 4–5 0.05 It is also assumed that the pre-fault voltage at the faulted bus is VF = 1.05e j0o p.u. Since machine subtransient reactances are used in the analysis, the currents to be calculated are then subtransient fault currents. The purpose of the analysis is to determine the subtransient fault currents and phase voltages in each bus when a three-phase short circuit occurs at bus 1. The calculations are then repeated for three-phase short circuits occurring at bus 2, 3, and so on. 3 j 0.02 Eg2
18 Applications of Spreadsheets in Education The Amazing Power of a Simple Tool, 2011, 18–40 Use of Spreadsheets for Analyses in Structural Engineering Nelson Lam Department of Civil and Environmental Engineering University of Melbourne, Parkville, Victoria, Australia CHAPTER 2 Address correspondence to: Dr. Nelson Lam, Department of Civil and Environmental Engineering, School of Engineering, University of Melbourne, Parkville 3010, Australia; Tel: (+61) 3-8344-7554; E-mail: ntkl@unimelb.edu.au Abstract: Structural engineering is a branch of engineering that is concerned with the analysis and design of elements such as beams, frames, trusses, and other mechanical structures whose principal function is to provide the necessary supporting feature to withstand the mechanical loads, or related operating conditions, normally associated with structures such as buildings, bridges, cranes, airplanes, and so on. This chapter concentrates on the analysis of beams, wall frames, and buildings. More specifically, the analyses of these structures are illustrated via Microsoft Excel spreadsheets. Spreadsheets may be used to develop quite sophisticated applications that can automate the intensive calculations commonly encountered in structural analysis. Keywords: structural analysis, beams, walls, frames, modal analysis. 2.1 Introduction Excel spreadsheets are widely used in design offices for providing assistances to the design of engineered structures. This type of spreadsheet program is typically used for accessing a database of design parameters (for the selection of products, for example) or to expedite the checking of the design against a list of criteria for ensuring code compliances. Essentially, Excel spreadsheets have been used as database managers to replace the tedious tasks of looking up design charts and tables manually, and for checking compliances. This chapter is also concerned with the application of Excel in structural engineering design and analysis, with an emphasis on the potential usage of the platform for educational purposes and for the more intensive analytical tasks that are traditionally performed by proprietary structural analysis packages. Such potential uses of Excel that are being explored in this chapter have not been widely recognized. Mark Lau and Stephen Sugden (Eds) All rights reserved – c○2011 Bentham Science Publishers Ltd.
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