This book describes the three major power system transients and dynamics simulation tools based on a circuit-theory approach that are widely used all over the world (EMTP-ATP, EMTP-RV and EMTDC/PSCAD), together with other powerful simulation tools such as XTAP. In the first part of the book, the basics of circuit-theory based simulation tools and of numerical electromagnetic analysis methods are explained, various simulation tools are introduced and the features, strengths and weaknesses are described together with some application examples. In the second part, various transient and dynamic phenomena in power systems are investigated and studied by applying the numerical analysis tools, including: transients in various components related to a renewable system; surges on wind farm and collection systems; protective devices such as fault locators and high-speed switchgear; overvoltages in a power system; dynamic phenomena in FACTS, especially STATCOM (Static Synchronous Compensator); the application of SVC to a cable system; and grounding systems. Combining underlying theory with real-world examples, this book will be of use to researchers involved in analysis of power systems for development and optimization, and professionals and advanced students working with power systems in general
Inspec keywords: EMTP; surges; flexible AC transmission systems; switchgear; power system transient stability; fault location; power convertors; finite difference time-domain analysis; wind power plants
Other keywords: wind power plant system; voltage-sourced converter; cable systems; XTAP; PEEC method; FDTD method; renewable energy system components; lightning surges; PSCAD-EMTDC; FACTS; circuit theory-based approach; SVC; high-speed switchgear; grounding system transients; numerical electromagnetic analysis; EMTP-ATP; protective devices; electromagnetic transients simulation; EMTP-RV; fault locator
Subjects: General electrical engineering topics; Inspection and quality control; Other numerical methods; Switchgear; a.c. transmission; Wind power plants; Power convertors and power supplies to apparatus; Power system control
This chapter describes first a circuit theory-based approach, EMTP in particular. Since it is based on the assumption of TEM mode propagation, a phenomenon associated with non-TEM mode propagation cannot be dealt with. Thus, the necessity of an NEA has become clear. The chapter explains existing NEA methods and the basic theory. The methods are categorized by either in time domain or in frequency domain. The latter one necessitates frequency to time transform such as Fourier transform to obtain a transient response. Also, the methods are classified by a given medium being partitioned by space or by the boundary between media. Phenomena involving scattering, radial wave propagation other than axial one, and non-TEM mode propagation cannot be solved by the circuit-theory approaches which are based on TEM mode propagation. The NEA is very advantageous to solve a transient involving non-TEM mode propagation which is three-dimensional in general. It should be noted that the NEA is very useful to calculate the impedance and the admittance of a given circuit which are essential in a transient simulation by the circuit-theory approach, but often are not available. This suggests adopting the NEA as a subroutine for calculating input data of the circuit-theory approach, when the data are not available. It should be pointed out that the NEA requires a large amount of computer resources, i.e., memory and CPU time. Also, existing codes are not general enough to deal with various types of transients especially in a large network.
EMTP-ATP (ElectroMagnetic Transients Program, version Alternative Transients Program) is a non-commercial digital simulation program for electromagnetic transients particularly in electrical power systems based on the royalty-free development of EMTP by Bonneville Power Administration (BPA) in Portland, Oregon, USA [1-3]. BPA was an agency of the U.S. Department of Energy. The roots of EMTP-ATP can be traced to early 1984, when it became apparent to BPA's EMTP developers that Development Coordination Group (DCG) was not working as it was supposed to, and formed a threat to free EMTP. DCG for EMTP was founded by a coordination agreement in 1982, originally with the intention to keep the EMTP proper in public domain. At that point 12 years of `EMTP Memoranda' were ended by Dr. Scott W. Meyer, and every available hour of his free time was switched from BPA's EMTP to the creation of a viable alternative that would be denied to those having commercial ambitions. ATP was the result during the fall of 1984. This followed Dr. Meyer's return from Europe, where the first European EMTP short course, in Leuven, Belgium, took place, and purchase of his first home computer, the new IBM PC AT, during August of 1984. The first annual meeting of Leuven EMTP Center (LEC) was held in Leuven on November 4, 1985, and Dr. Meyer agreed to bring the EMTP-ATP.
This chapter presented a summary on numerical methods used in EMTP (EMTPRV version) for the computation of electromagnetic transients. EMTP offers several options and modules for the simulation and analysis of complex power systems. EMTP offers a unified environment that can be applied to study power systems from steady-state conditions, to electromechanical and electromagnetic transients.
The development of EMTDC and its PSCAD operations interface with its associated software and its present capabilities are illustrated. The new simulation methods and tools to study complex power electronics applications in power systems are described. In addition, PSCAD has the ease in building user-defined models and can interface with other useful modelling and graphical software. Also, the latest application examples to cable transients are demonstrated. The changing nature of electric power systems and associated equipment, including transportation, industrial requirements, and power electronic/control systems, are able to be studied and designed with PSCAD. Very large electric grids are accommodated with parallel processing and hybrid simulation. Equipment supplier's confidential models of their equipment can be included in a model under secured conditions. PSCAD continues to be aggressively developed to meet the requirements of the developing power system industry so much dependent on power electronics.
Power system engineers started using object-oriented methods for power system simulations in the late 1980s. Object-oriented methods are now used in various aspects of power system simulations. In, an object-oriented implementation of a load-flow program using the Objective-C language is illustrated. How power system components such as transmission lines, transformers, etc. are modeled using classes is explained, and it is concluded that the object-oriented approach reduces the efforts of programming.
In this chapter, applications of the FDTD method to lightning electromagnetic field and surge simulations are reviewed. The structure of this chapter is as follows. In section 6.2, the fundamental theory of the FDTD method is briefly described, and advantages and disadvantages of the FDTD method in comparison with other representative NEA methods are identified. In section 6.3, seven representations of the lightning return-stroke channel used to date are described. In section 6.4, representative applications of the FDTD method are reviewed. They include simulations of (i) lightning electromagnetic fields at close and far distances, (ii) lightning surges on overhead power transmission lines and towers, (iii) lightning surges on overhead power distribution lines, (iv) lightning electromagnetic environment in power substations, (v) lightning electromagnetic environment in airborne vehicles, (vi) lightning surges and electromagnetic environment in buildings, and (vii) surges on grounding electrodes.
The conventional full-wave formulation of the partial element equivalent circuit (PEEC) method was derived from the mixed-potential integral equation (MPIE) for the free space by A. E. Ruehli in 1974. The final results are interpreted Maxwell's equations to a circuit domain by inductance, capacitance, and resistance extraction including retardation in theory. In that time, the retardation is neglected because the minimum wavelength corresponding to the considered maximum frequency is longer than dimensions of an interested domain. His development is based on the concept of inductance and capacitance extraction, which was firstly introduced by Rosa in 1908, and further developed by Grover in 1946 and Hoer and Love in 1965. Despite the fact that the PEEC method has an exact field theoretical basis, it was not primarily developed for the computation of electromagnetic fields. Instead, the circuit designer has a tool at hand to analyze the parasitic effects on connecting structures of circuits without leaving the familiar area of a network theory. This method was considerably developed further in the 1990s where retardation, external field excitation, and the treatment of a dielectric material were investigated.
In recent years, the steady increase of the number of wind turbines (WTs) has resulted in many accidents caused by natural phenomena such as lightning and typhoons. In particular, this section focuses on the extensive damage on WTs caused by lightning. In order to benefit from better wind conditions, WTs are often constructed on hilly terrain or at the seashore where few other tall structures exist; therefore, WTs are often struck by lightning. For promoting wind power generation, lightning protection methodologies should be established for WTs. To establish the lightning protection methodologies, a number of simulation methods have been proposed. The simulation results are compared, in general, with measured results, and the accuracy and effectiveness are verified. In this section, numerical analyses of surge phenomena on a WT are introduced.
In this chapter, lightning surge analyses on a WPP were performed using ARENE (section 9.5) and PSCAD/EMTDC (section 9.6). The analyses simulated a WPP using a simple model with WTs, boost transformers, SPDs, and a gird-interactive transformer connected with a collection system. From the results of several analyses the following conclusions were obtained: (1) A back-flow surge can propagate to other WTs from the WT that has been directly struck by winter lightning via the earthing system and the collection line in a WPP. (2) Burnout incidents of SPDs could quite easily occur even in a WT far from the lightning-struck WT. (3) Installing multiple earthing wires to the collection line in a WPP can reduce the burnout incidents due to winter lightning. (4) The earthing wire may not help, especially for summer lightning, to reduce the EPR (earth potential rise) of WTs and the grid-interactive transformer.
This chapter has investigated the influence of the fault arc nonlinearity and the input device error on the accuracy of digital fault locators. A time domain simulation model of the digital fault locator was represented using the MODELS language in the ATP-EMTP. Various types of faults were simulated with constant and nonlinear fault arc resistances. The simulation results have shown that the impedance relay type method is influenced by the nonlinear characteristics of the fault arc, while the current diversion ratio method is not. A sensitivity analysis of the locating error with respect to the model parameters of the nonlinear arc resistance was performed for the impedance relay type method. It has been observed that the greater the degree of nonlinearity, the greater the location error. CT errors were considered, and it was observed that the CT saturation error does not last long enough to affect the fault location result and thus can be ignored.
The surge arrester at the line entrance must be installed for the protection from fast-front overvoltages. The selected surge arrester in the simulation model has a sufficient performance for the assumed lightning strike and other conditions. The standard rated lightning impulse withstand voltage can be selected from 1,050, 1,175, 1,300, and 1,425 kV for the equipment whose highest overvoltage is 420 kV. From the simulation results in this example, it is normally recommended to select 1,300 or 1,425 kV. The selection of 1,175 kV depends on the choice of a safety margin. For the final selection of the withstand voltages and surge arresters, it is also required to perform the temporary overvoltage analysis and the slow-front overvoltage analysis.
FACTS (Flexible AC Transmission Systems) was advocated by Dr. Narain G. Hingorani in 1998 [1]. This system is a power electronics device applicable to a power grid. Since FACTS can control power and reactive power positively compared to general transmission devices, it gives flexibility to the power grid in resolving the problems of the power grid. It is one of the effective countermeasures for the stability problems and voltage problems of the power grid. FACTS technology has also received a lot of attention for the countermeasures for enhancement of renewable energy in the power grid [2-4]. When the renewable energy is connected to the power grid, local problems such as a voltage fluctuation by wind power may become obvious. FACTS is the effective device for the countermeasure for renewable energy also.
Interconnection to the island from the mainland has advantages as follows. The electric power on remote islands, in general, has been provided by power generation on the islands, which requires maintenance and fuel transport for the generators. If the mainland and the remote island are connected by submarine cables and power is transmitted from the mainland, there are economic advantages since the costs of maintenance and fuel for generators on the island can be reduced.
Grounding plays a relevant role in the operation of electrical power systems. Notably, when electrical systems are subjected to transient phenomena resulting from internal or external events, the response of these systems might be strongly influenced by the behavior of their ground terminations [1]. In order to assess how the ground terminations influence this response, one must first understand the transient response of the grounding electrodes, which is quite different from that observed when electrodes are subjected to slow phenomena, such as short circuits. This chapter addresses this issue throughout five sections, by means of a conceptual approach illustrated with the analysis of a specific application.