Showing papers in "IEEE Transactions on Power Apparatus and Systems in 1976"
TL;DR: A truncated dynamic programming method for the commitment of thermal units over a period of up to 48 hours is described, such that the total cost is minimal.
Abstract: Fuel cost savings can be obtained by proper commitment of the available generating units. This paper describes a truncated dynamic programming method for the commitment of thermal units over a period of up to 48 hours. The commitment is such that the total cost is minimal. The total cost includes both the production cost and costs associated with the startup and shutdown of units. The startup cost for each unit is dependent on the amount of time the unit has been shutdown prior to startup. A variety of spinning reserve requirements are observed and crew constraints on the startup and/or shutdown of two or more units in the same plant are imposed on some of the plants. In addition, operation of individual units must satisfy the specified minimum up times and minimum shutdown times.
238 citations
TL;DR: In this paper, a method is introduced for the determination of the sparkover voltage of practically any configuration subjected to switching impulses of any polarity, applied to one or more electrodes When the discharge process is governed by the phenomena occurring at a positively charged electrode.
Abstract: A method is introduced for the determination of the sparkover voltage of practically any configuration subjected to switching impulses of any polarity, applied to one or more electrodes When the discharge process is governed by the phenomena occurring at a positively charged electrode. The method is applied to some configurations, especially chosen to show its important features, and the results obtained are compared with actual test results. It is finally shown which are the directions in which the studies on the discharge phenomenon could improve the precision and the applicability of the method.
184 citations
TL;DR: In this article, a general three phase load flow program is developed for the steady state analysis of any electric transmission network under all possible imbalance conditions such as untransposed EHV lines, single phase loading, single pole switching, etc.
Abstract: The paper describes a general three phase load flow program developed for the steady state analysis of any electric transmission network under all possible imbalance conditions such as untransposed EHV lines, single phase loading, single pole switching, etc. Input data preparation and output data interpretation are made easy for program users by using both phase and symmetrical components quantities; however, the load flow problem formulation and solution are all done in phase quantities (A, B, C). The method of solution is the Newton-Raphson method, using optimally ordered triangular factorization to take advantage of the sparsity of network equations. The program has several new features to simulate real three phase operation of power systems and imbalance conditions. For example, the internal induced voltages of generators are balanced, while generator terminal voltages depend on internal machine impedances and the imbalance in machine currents. Also, the steady state performance of the voltage regulator is simulated to maintain some function of the machine terminal phase voltages constant, depending on the actual design of the voltage measurement. Another feature of the program is that it can handle all common transformer connections having two or three windings that are used in HV transmission networks.
114 citations
TL;DR: In this paper, a new algorithm is described to solve the static, time-invariant weighted least-square state estimation problem for large-scale electric power systems, which is obtained through P-θ and Q-V decoupling and alternately iterating the active and reactive equations using fixed, simplified submatrices of the information matrix.
Abstract: A new algorithm is described to solve the static, time-invariant weighted least-square state-estimation problem for large-scale electric power systems. The solution is obtained through P-θ and Q-V decoupling and alternately iterating the active and reactive equations using fixed, simplified submatrices of the information matrix. Thus, a much faster algorithm is obtained yielding the exact solution and requiring little computer storage. The new method is compared with the basic "Weighted-least-square" and the "Line-Only" algorithms on a practical HV network.
104 citations
TL;DR: In this paper, the authors describe the research and development work being done at the AEP Service Corp. on digital computer applications in EHV substations, including relaying of transmission lines and other power system equipment, station alarm monitoring and data logging, oscillography, and supervisory control functions.
Abstract: This paper describes the research and development work being done at the AEP Service Corp. on digital computer applications in EHV substations. Relaying of transmission lines and other power system equipment, station alarm monitoring and data logging, oscillography, and supervisory control functions are considered for possible computer implementation. A new algorithm for computing the impedance as seen from the terminals of a faulted transmission line is presented. Results obtained with the new algorithm for faults simulated with a model transmission line are included in the paper. Field experience obtained from operating a minicomputer in an EHV substation is also described.
100 citations
TL;DR: In this paper, the authors describe analytical and experimental results for a new method of current harmonic reduction in thyristor converters, which is based on modifying the current waveforms on the d.c. windings of the converter transformer by injecting harmonic currents at a particular frequency.
Abstract: The paper describes analytical and experimental results for a new method of current harmonic reduction in thyristor converters. The principle of the method is to modify the current waveforms on the d.c. windings of the converter transformer by injecting harmonic currents at a particular frequency. In practice, third harmonic currents of the power frequency is most efficient. Experimental results carried out prove that the method is effective in reducing the alternating-current harmonics, and that it is applicable to any type of thyristor converters.
100 citations
TL;DR: In this paper, a control algorithm for small-signal modulation of the Pacific HVDC Intertie is described, which is applied to the current regulator at the sending end of the dc intertie.
Abstract: Recent undamped oscillations in the Western U.S. power system have indicated the need to improve system damping. The development of a control algorithm for small-signal modulation of the Pacific HVDC Intertie is described. The control signal which would be applied to the current regulator at the sending end of the dc intertie is based on rate of change of ac-intertie power. Results from simulation studies are presented which show that modulation will produce considerable damping.
91 citations
TL;DR: In this article, the effects of circuit breaker reclosing, both successful and unsuccessful, and faulty synchronizing on the life expenditure of rotor materials are evaluated. But the effect of repeated instances of such over-stressing on rotor materials is not evaluated.
Abstract: Recent concern over abnormal stresses imposed on the shafts of large turbine-generators, due to high speed switching of network faults, has led to intensive investigation of this phenomenon. Elaborate computer programs were developed for simulated model studies which revealed that hitherto unexpectedly high shaft stresses can occur merely by tripping a three-phase short circuit near the power station at an unfavorable instant. The effects of circuit breaker reclosing, both successful and unsuccessful, were also investigated together with those due to faulty synchronizing. Test data on a 780 MVA unit gained by telemetric means verified the calculated torques and established the damping coefficients in a running unit. The adverse influence of numerous repetitive instances of such over-stressing on life expenditure of rotor materials is being evaluated.
85 citations
TL;DR: The symmetry of the induction machine can be exploited to obtain general closed form expressions for the small signal transfer functions describing speed, voltage, frequency, or load perturbations by utilizing the complex time variables introduced by Ku and Lyon in the 1950's as discussed by the authors.
Abstract: The symmetry of the induction machine can be exploited to obtain general closed form expressions for the small signal transfer functions describing speed, voltage, frequency, or load perturbations by utilizing the complex time variables introduced by Ku and Lyon in the 1950's. After a brief introduction to complex variables, the linearlzed complex variable equations describing small signal dynamic performance are presented. These equations are used to obtain transfer functions in which the effects of excitation level are isolated in the gain factors. The speed and frequency dependence of the poles and zeros is expressed in closed form employing a useful non-dimensional parameter system. To illustrate the application of these results, the dynamic behavior of the induction machine without feed-back control is analyzed. It is shown that the general dynamic response can be characterized by the non-dimensional loop gain and stator frequency. A set of general non-dimensional root loci are presented which permit rapid estimation of the relative stability (dominant eigenvalues) and the frequency of minimum damping of any specific machine. The application of the transfer functions to cases involving feedback control of the machine is also discussed.
78 citations
TL;DR: In this paper, a method of representing a group of induction motor loads by a single unit equivalent is described, and the dynamic performance of the composite group following supply disturbances is examined using the single unit model.
Abstract: The paper describes a method of representing a group of induction motor loads by a single-unit equivalent. The dynamic performance of the composite group following supply disturbances is examined using the single unit model. The representation employs the induction motor steady state equivalent circuit mad allows for effects of inertia and mechanical load characteristics. Experimental results are presented and compared with corresponding theoretical results using the proposed method as well as classical techniques of analysis. Sudden and gradual supply disturbances are considered, and different load torque-speed characteristics.
76 citations
TL;DR: In this article, an axially blown arc is studied under physical conditions typical of HV circuit breakers, where the current is ramped down with adjustable slope after a stationary phase.
Abstract: An axially blown arc is studied under physical conditions typical of HV circuit breakers. The experiment is especially designed to produce a stable and reproducible arc with good accessability for diagnostics. After a stationary phase the current is ramped down with adjustable slope. The vicinity of current zero is especially investigated. For the first time, the most effective recovery zone is localized and its physical parameters are evaluated. The limiting curve for thermal reignition is determined. Based on the observed phenomena a theoretical description is derived which explains quite well the experimentally known extinction characteristics of this type of arc.
TL;DR: In this paper, the DC converters and transmission lines are incorporated directly into the Jacobian of the Newton power flow, and the DC equations are presented in a per unit form compatible with the per unit AC equations.
Abstract: This paper presents the method used to include the equations for DC converters and transmission lines directly in a Newton AC system power flow. The DC equations are presented in a per unit form that is compatible with the per unit AC equations. The DC equations can therefore be incorporated directly into the Jacobian of the Newton power flow. The convergence properties of the Newton method are not altered. The DC model and equations used make it possible to investigate any number of two terminal DC lines or multiple terminal DC networks as component parts of an AC system.
TL;DR: In this paper, calculated and measured transmission line electrostatic and electromagnetic fields are presented and compared to measured values, where the 30 line rotating E and B vectors were presented as vector loci and the phasor space potentials are presented as mappings.
Abstract: Calculated and measured transmission line electrostatic and electromagnetic fields are presented. The 30 line rotating E and B vectors are presented as vector loci and the phasor space potentials are presented as mappings. Lateral profiles of ground level electrostatic and electromagnetic fields are calculated and compared to measured values.
TL;DR: In this article, a methodology for constructing high fidelity models of magnetic hysteresis that can be used in digital studies of network transients is presented, and an illustrative example is included.
Abstract: This paper presents a methodology for constructing high fidelity models of magnetic hysteresis that can be used in digital studies of network transients. An illustrative example is included.
TL;DR: A highly efficient method for digital calculation of transients on transmission lines with frequency-dependent effects is presented, and the total computation time of a transient calculation is easily reduced by half compared with conventional methods for calculating transmission line transients.
Abstract: A highly efficient method for digital calculation of transients on transmission lines with frequency-dependent effects is presented. The most time consuming part of calculating the transmission line transients in time-domain techniques such as traveling-wave methods is numerical evaluation of real-time convolution for including the frequency-dependent effects of the transmission lines. In the new method developed in the paper, a time response of a frequency-dependent parameter is simulated with linear curves. Then, the convolution in time-domain is evaluated by a sum of very few multiplications of the time response and a traveling-wave variable in which the effect of the frequency dependent parameter is to be included. Computation time required for the convolution is reduced to much less than one tenth, and the total computation time of a transient calculation is easily reduced by half compared with conventional methods for calculating transmission line transients.
TL;DR: In this paper, a numerical dc field mapping method for electric field analysis of two-dimensional configurations which consist of composite insulation and field mapping methods under combined ac-dc voltage and dc reversed polarity voltage were proposed.
Abstract: Breakdown characteristics of insulating oil, under combined ac-dc voltage and dc reversed polarity voltage, and partial discharge characteristics of oil-immersed insulation, under combined ac-dc voltage and polarity revesal of dc voltage Were made clear by elementary experiments. After that, a numerical dc field mapping method for electric field analysis of two-dimensional configurations which consist of composite insulation and field mapping methods under combined ac-dc voltage and dc reversed polarity voltage were proposed. Futhermore, partial discharge characteristics of transformer insulation under dc, combined ac-dc voltage were experimentally made clear by practical trial models.
TL;DR: The problem of estimating the increase in computational effort as the system size n increases is studied for methods requiring the solution of Ax = b, where A is sparse and topology-symmetric.
Abstract: The problem of estimating the increase in computational effort as the system size n increases is studied for methods requiring the solution of Ax = b, where A is sparse and topology-symmetric. The expected value of the total number of upper triangular nonzero elements after factorization is assumed to grow as n1+γ. The expected computational effort for the factorization itself is shown to grow as n1+2γ, while the one for each repeat solution is shown to grow as n1+γ. Values of γ for typical power systems are experimentally determined by generating a variety of random networks and ordering the resultant matrices according to "scheme 2". For typical power systems a reasonable value for γ is 0.2. Therefore, methods requiring repeated refactorization of A (such as Newton's method) can be expected to increase as n1.4, while methods requiring merely repeat solutions (such as fast decoupled methods) can be expected to increase as n1.2. Several other important comparisons are included.
TL;DR: In this article, the influence of surface roughness on the onset or breakdown voltage in air and SF 6 was investigated by applying the streamer theory of electrical discharges and considering the role of ionization characteristic, gas pressure, shape and size of electrode surface protrusions.
Abstract: This paper describes investigations on the influence of surface roughness on the onset or breakdown voltage in air and SF 6 . Applying the streamer theorie of electrical discharges the role of ionization characteristic, gas pressure, shape and size of electrode surface protrusions is discussed. The maximum allowable field gradients of electrode surfaces with hemispherical, spherical, and filamentary irregularities were computed in air and SF 6 . Pictures of a sparked electrode surface, showing slze and shape of surface roughness, were made using an electron scanning microscope. A comparison between computed breakdown field gradients of rough electrodes and experimental results obtained by employing different electrode configurations in a wide pressure range confirmed the theoretical considerations.
TL;DR: In this article, the authors developed the joint use of several new concepts for improving stability, reliability, and safety of a double-circuit three-phase EHV line: 1. Use of selectivepole switching; that is, only the faulted conductors are opened and reclosed.
Abstract: This paper develops the joint use of several new concepts for improving stability, reliability, and safety of a double-circuit three-phase EHV line: 1. Use of selective-pole switching; that is, only the faulted conductors are opened and reclosed. 2. Exclusive use of that arrangement of conductors that gives the least current to ground from a large vehicle capacitively coupled to the line: like phases are in diagonally opposite positions. 3. Use of bank of 3 shunt capacitors and 9 shunt reactors for neutralizing the 15 interconductor capacitances and thereby eliminating the shunt capacitive coupling that tends to maintain the secondary fault arc. 4. Sectionalizing the faulted conductor or conductors into two or more longitudinal sections by remote-controlled switches in order to reduce the longitudinal resistive-inductive coupling that also tends to maintain the secondary fault arc. These concepts are illustrated by applying all of them to a simulated 735-kV, heavily loaded, 200-mile line having 6 bundles of 4 Chukar conductors each.
TL;DR: This paper analyzes and modifies the existing method of IEEE Guide No. 80, to allow a recursive point by point integration of surface gradients through consecutive meshes, and describes a computer program for optimized grid design.
Abstract: The envelope of earth surface potential curves is distinctly convex for grounding mats with many meshes. Such a condition is difficult to analyze with the established methods, which are primarily devised for calculating the corner mesh voltage. For this reason, a large, equally spaced grid may be overdesigned toward the center and underdesigned toward the perimeter. Aiming to remedy such problems, this paper analyzes and modifies the existing method of IEEE Guide No. 80, to allow a recursive point by point integration of surface gradients through consecutive meshes. A computer program for optimized grid design is described and the effect of spacing geometry is documented by computer plotted voltage profiles.
TL;DR: In this paper, a mechanism of the generation of water trees is discussed in detail and critical values to judge the level of insulation quality are recommended as 0.01 ω. F for electrical resistance and 5% for tan δ.
Abstract: Insulation of 3.3 kV and 6.6 kV XLPE and PE cables was found to be mechanically stressed by 20 to 100 kg/cm2during the process of water tree formation. Infrared absorption curves change if water trees are created. A mechanism of the generation of water trees is discussed in detail. Critical values to judge the level of insulation quality are recommended as 0.01 ω. F for electrical resistance and 5% for tan δ. A lifetime curve is presented to estimate remaining lifetime of cables with water trees.
TL;DR: In this article, various methods which solve accurately the most general problem of interconnected electrodes are presented and discussed, including Multi-Step Analysis (MSA) and Multi-step Analysis (MSA).
Abstract: Exact determination of current distribution along a grounding electrode is, in all practical purpose, only solvable by successive approximations. In this paper various methods which solve accurately the most general problem of interconnected electrodes are presented and discussed. One of these methods called herein the Multi Step Analysis seems to have definitive advantages with respect to accuracy, computing time and simplicity. It is hoped that the following will be helpful for those who are concerned with a reasonable accurate design of grounding networks which takes into account the overall parameters of the system.
TL;DR: In this paper, a method for computing exactly the frequency and duration of load loss events as measures of generating system reliability is presented, which utilizes an exact state capacity model together with a cumulative state load model which requires no idealization.
Abstract: The paper presents a method for computing exactly the frequency and duration of load loss events as measures of generating system reliability. The method utilizes an exact state capacity model together with a cumulative state load model which requires no idealization. Efficient computer algorithms for building the exact state capacity model and computing the system reliability indices are presented.
TL;DR: In this paper, the step response of three-phase pipe-type cable is determined for cradled and triangular configurations and the Fast Fourier Transform is used for calculation, dramatically reducing computation time.
Abstract: The step response of three-phase pipe-type cable is determined. The solution techniques are closed form and analogous to those developed by Carson for overhead transmission lines. Results are shown for cradled and triangular configurations. The Fast Fourier Transform is used for calculation, dramatically reducing computation time. Delay of the zero sequence wave and attenuation of all components are shown. Calculations neglect saturation of the pipe wall, which follows in a later paper. The results can be incorporated into existing digital transients programs or be used to construct complex frequency-dependent analog models for Transient Network Analyzer (TNA)Studies.
TL;DR: The results of an electrostatic measurements program held in conjunction with the IEEE Working Group on E/S and E/M Effects of Transmission Lines and attended by representatives of several organizations are presented as discussed by the authors.
Abstract: The results of an electrostatic measurements program held in conjunction with the IEEE Working Group on E/S and E/M Effects of Transmission Lines and attended by representatives of several organizations are presented. Measurements were made at ground level under an energized 525-kV line of electric field intensity, of induced currents and voltages on objects, and of perception and annoyance levels of men, women, and children for steady state and transient shocks. Three types of field strength meter were employed. They gave consistent readings in agreement with predicted field strength. Analytical estimates of short circuit current for various objects are in agreement with measured values.
TL;DR: In this paper, a digital computer method for obtaining eigenvalue sensitivities of interconnected power systems is presented, especially suited to the analysis of detailed modelled synchronous machine systems where shaft and stator-network dynamic effects are significant.
Abstract: A practical digital computer method for obtaining eigenvalue sensitivities of interconnected power systems is presented. The method is especially suited to the analysis of detailed modelled synchronous machine systems where shaft and stator-network dynamic effects are significant. A unified structure in the construction of the state space equations permits the inclusion of a wide variety of control equipment and varying degrees of modelling complexity. Sample results are given for typical cases illustrating the significance of eigenvalue sensitivities. Specifically results are presented for a 4 generator hydroelectric system and for a 2 generator system exibiting subsynchronous torsional resonance.
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TL;DR: In this article, the effects of generator position and load location on damping efficiency were analyzed, as well as the effect of load location and load characteristics on the damping improvement that may be expected from additional feedback in excitation control.
Abstract: Power systems with longitudinal structure may be subjected to poorly damped oscillations at low frequencies; the structure of speed governors and of excitation controls may have a considerable influence on damping of these oscillations. The strong influence of generator position on damping efficiency is analyzed, as are the effects of load location and load characteristics on the damping improvement that may be expected from additional feedback in excitation control. Some schematizations make it possible to obtain a qualitative insight into the influence of different parameters on oscillation damping. An example of slow oscillation damping in the Italian system is given.
TL;DR: In this article, the authors used computerized magnetic field solutions, based on magnetic vector potential, to develop a simplified approach to the calculation of saturated values of steady state reactances of turbogenerators under various load conditions.
Abstract: This paper details the use of computerized magnetic field solutions, based on magnetic vector potential, to develop a simplified approach to the calculation of saturated values of steady state reactances of turbogenerators under various load conditions. When magnetic nonlinearity of the stator and rotor materials is taken into account, the turbogenerator reactances become dependent on the saturation conditions in the machine, which are a function of the operating conditions (terminal voltage, current and power factor). Quadrature axis synchronous reactances are reduced by as much as 40% from their classical unsaturated values under rated load. Torque angles deduced from the model at rated load are lower by as much as 20% than values obtained by standard methods. The method is applied to two typical 4-pole, 659 MVA and 2-pole, 733 MVA turbogenerators of the gas inner-coaled type. Supportive shop floor test results are provided.
TL;DR: In this paper, the authors defined impedances for all conductors which constitute a submarine single-core cable: the central conductor, the metallic sheath, the reinforcement if any, the armor and the sea.
Abstract: Impedances are defined for all conductors which constitute a submarine single-core cable: the central conductor, the metallic sheath, the reinforcement if any, the armor and the sea. Impedances of magnetic armor are considered in some detail and relevant numerical data are given. The presence of other cables, far apart in the sea, is taken into consideration. Rules for composition of impedances are given, from which the additional losses of the cable and the distribution of current between various conductors are computed.
TL;DR: In this article, a three-dimensional finite element solution of the scalar potential problem is described for the heat flow problem in the stator cores of large generators, and the shape functions and exact solution matrices are derived algebraically for utmost economy in computation.
Abstract: A three-dimensional finite element solution of the scalar potential problem is described. The shape functions and exact solution matrices are derived algebraically for utmost economy in computation. The method of application to the heat flow problem in the stator cores of large generators is indicated.