Transient Analysis of Power Systems

A Practical Approach

Juan A. Martinez-Velasco, Juan A. Martinez-Velasco

• Publisher: Wiley-IEEE Press
• Year: 2019
• ISBN:
  9781119480495
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Risorse energetiche

A hands-on introduction to advanced applications of power system transients with practical examples

Transient Analysis of Power Systems: A Practical Approach offers an authoritative guide to the traditional capabilities and the new software and hardware approaches that can be used to carry out transient studies and make possible new and more complex research. The book explores a wide range of topics from an introduction to the subject to a review of the many advanced applications, involving the creation of custom-made models and tools and the application of multicore environments for advanced studies.

The authors cover the general aspects of the transient analysis such as modelling guidelines, solution techniques and capabilities of a transient tool. The book also explores the usual application of a transient tool including over-voltages, power quality studies and simulation of power electronics devices. In addition, it contains an introduction to the transient analysis using the ATP. All the studies are supported by practical examples and simulation results. This important book:

• Summarises modelling guidelines and solution techniques used in transient analysis of power systems
• Provides a collection of practical examples with a detailed introduction and a discussion of results
• Includes a collection of case studies that illustrate how a simulation tool can be used for building environments that can be applied to both analysis and design of power systems
• Offers guidelines for building custom-made models and libraries of modules, supported by some practical examples
• Facilitates application of a transients tool to fields hardly covered with other time-domain simulation tools
• Includes a companion website with data (input) files of examples presented, case studies and power point presentations used to support cases studies

Written for EMTP users, electrical engineers, Transient Analysis of Power Systems is a hands-on and practical guide to advanced applications of power system transients that includes a range of practical examples.

Chapter 1
Introduction to Transients Analysis of Power Systems with ATP

Juan A. Martinez‐Velasco

1.1 Overview

Transient analysis has become a fundamental methodology for understanding the performance of power systems, determining power component ratings, explaining equipment failures, or testing protection devices. The study of transients is a mature field that can help to analyse and design modern power systems.

A significant effort has been dedicated to the development of new techniques and software tools adequate for transient analysis of power systems. Sophisticated models, complex solution techniques, and powerful simulation tools have been developed to perform studies that are of paramount importance in the analysis and design of modern power systems. Current tools for transient analysis can be applied into a myriad of studies (e.g. overvoltage calculation, flexible AC transmission systems (FACTS) and Custom Power applications, protective relay performance, power quality studies) for which detailed models and accurate solutions can be crucial.

Transient phenomena in power systems are associated with disturbances caused by faults, switching operations, lightning strikes, or load variations. These phenomena can stress and damage power equipment. The importance of their study is basically due to the effects they can have on the system performance or the failures they can cause to power equipment. Therefore, protection against these stresses is necessary. This protection can be provided by specialized equipment whose operation is aimed at either isolating the power system section where the disturbance has been originated (e.g. a power component failure that causes short‐circuit) or limiting the stress across power equipment terminals (e.g. by installing a surge arrester that will mitigate voltage stresses). In addition, a better performance against stresses caused by transient phenomena can be also achieved with an adequate design of power equipment (e.g. by shielding overhead transmission lines to limit flashovers caused by direct lightning strokes). That is, although the power system operates most of the time under normal conditions, it must be designed to cope with the consequences associated to transient phenomena.

A rigorous and accurate analysis of transients in power systems is difficult due to the size of the system, the complexity of the interaction between power devices, and the physical phenomena that need to be analysed. Aspects that contribute to this complexity are the variety of causes, the nature of the physical phenomena, and the timescale of power system transients. In order to select an adequate protection against any type of stress, it is fundamental to know their origin, calculate their main characteristics, and estimate the most adverse conditions. Disturbances can be external (lightning strokes) or internal (faults, switching operations, load variations). Power system transients can be electromagnetic, when it is necessary to analyse the interaction between the (electric) energy stored in capacitors and the (magnetic) energy stored in inductors, or electromechanical, when the analysis involves the interaction between the energy supplied by sources, the electric energy stored in circuit elements, and the mechanical energy stored in rotating machines. To accurately analyse physical phenomena associated with transients, it is necessary to examine the power system for a time interval as short as a few nanoseconds or as long as several minutes. This is a challenge since the behaviour of power equipment is very dependent on the transient phenomena; namely, it depends on the range of frequencies associated to transients. Despite the powerful numerical techniques, simulation tools, and graphical user interfaces (GUIs) currently available, those involved in transients studies, sooner or later, face limitations of those models available in transients packages, the lack of reliable data and conversion procedures for parameter estimation, or insufficient studies aimed at validating models.

Figure 1.1 depicts the steps of a typical procedure when simulating transients in power systems [1].

1. 1. The selection of the study zone and the most adequate representation of each component involved in the transient. The system zone is selected taking into account the frequency range of the transients to be simulated: the higher the frequencies, the smaller the zone modelled. In general, it is advisable to minimize the study zone since a larger number of components does not necessarily increase accuracy; instead it will increase the simulation time and there will be a higher probability of insufficient or incorrect modelling. Although a high number of works has been dedicated to provide guidelines on these aspects [2–4], some expertise is necessary to choose the study zone and the models.
2. 2. The estimation of parameters to be specified in the mathematical models. Once the mathematical model has been selected, it is necessary to collect the information that could be useful to obtain the values of parameters to be specified. Details about parameter determination of some power components were presented in [5]. A sensitivity study should be carried out if one or several parameters cannot be accurately determined. Results derived from such study will show which parameters are of concern.
3. 3. The application of a simulation tool. The steadily increasing capabilities of hardware and software tools have led to the development of powerful simulation tools that can cope with large and complex power systems. Modern software for transient analysis incorporates friendly GUIs that can be very useful when creating the input file of the test system model.
4. 4. The analysis of results. Simulation of electromagnetic transients can be used, among others, for determining component ratings (e.g. insulation levels or energy absorption capabilities), testing control and protection systems, validating power component representations or understanding equipment failures. A deep analysis of simulation results is an important aspect of the entire procedure since each of these studies may involve an iterative procedure in which models and parameters values must be adjusted.

Figure 1.1 Simulation of transients in power systems [1].

Readers interested in transients analysis can consult specialized literature [3,6–18].

1.2 The ATP Package

ATP is an acronym that stands for Alternative Transients Program [19]. The ATP package is integrated by at least three tools: (i) ATPDraw, a GUI for creating/editing input files [20,21]; (ii) TPBIG, the main processor for transients and harmonics simulations; (iii) one postprocessor for plotting simulation results. Actually, ATP users can also take advantage of other tools (e.g. ATP Control Center and ATPDesigner [22] which can be used as a control center for the entire package) or add other tools that can be useful for some specific tasks.

ATPDraw is an interactive Windows‐based program that can act as a shell for the whole package; that is, users can control the execution of all modules integrated in the package from ATPDraw. As for the postprocessor, several tools have been developed to obtain graphical results (e.g. PCPlot, TPPLOT, GTPPLOT, TOP, PlotXY, ATP Analyzer), and it is possible to run most of them from ATPDraw. The most popular postprocessor among ATP users is PlotXY, developed by Maximo Ceraolo (University of Pisa, Italy) [23]. TOP (The Output Program), a royalty‐free tool created by Electrotek Concepts, is the postprocessor used with most of the case studies presented in this book [24].

The acronym ATP was initially used to denote the transients simulation tool here named TPBIG. Presently, many users use ATP to indistinctly nam...