Showing papers in "IEEE Transactions on Power Apparatus and Systems in 1972"
TL;DR: The development of a model suitable for power system operation over periods of time of the order of one or more years and based on probability techniques is described.
Abstract: The optimisation of power system operation over periods of time of the order of one or more years requires simulation models which combine reasonable accuracy with high computation speed The development of a model suitable for such studies and based on probability techniques is described
311Â citations
TL;DR: A new technique for solving the differential equations with the implicit trapezoidal rule of integration can be combined into one simultaneous solution, thereby eliminating the problem of interface error between the differential and algebraic equation solutions of the traditional approach.
Abstract: Techniques are described for improving the speed of large transient stability studies without sacrificing accuracy. A fast iterative method for solving the algebraic network equations, including the effect of generator saliency, is explained. A new technique for solving the differential equations with the implicit trapezoidal rule of integration is introduced. These two techniques can be combined into one simultaneous solution, thereby eliminating the problem of interface error between the differential and algebraic equation solutions of the traditional approach.
231Â citations
TL;DR: In this paper, a new method is developed to determine the weighting matrix Q of the performance function in conjunction with a left shift of the dominant eigenvalues as far as the practical controllers permit.
Abstract: For an optimal linear regulator design a performance function of the quadratic form must be chosen. The question arises of how to decide the weighting matrix Q of the performance function. A new method is developed in this paper to determine Q in conjunction with a left shift of the dominant eigenvalues as far as the practical controllers permit. The method is then applied to the optimal control design of a typical power system. Three cases are investigated, the first with an optimal excitation control uE, the second with optimal governor controls uG and uG, with and without the dash-pot, and the third with uE plus uG control. The stabilizing signals thus obtained are given nonlinear tests on the same power system. It is found from the results that the optimal controls are more effective than conventional excitation control, that the optimal governor control without dash-pot is just as good as the optimal excitation control, and that the optimal uE plus uG control is the best way to stabilize a power system.
183Â citations
TL;DR: In this article, the results of a dynamic optimization procedure in the design of load and frequency control (LFC) of power systems are presented, based on the optimal linear regulator theory, accommodated to satisfy the performance objectives of the LFC in large multi-area interconnections.
Abstract: The results of a dynamic optimization procedure in the design of load and frequency control (LFC) of power systems are presented. This design is based on the optimal linear regulator theory, accommodated to satisfy the performance objectives of the LFC in large multiarea interconnections. A proportional-plus-integral control law is considered. The paper also analyzes the influence of system and design parameters on power system performance considering two-and three-area interconnections. Finally, the problems of implementation are discussed.
153Â citations
TL;DR: The compensation theorem is applied in conjunction with ordered triangular factorization of the nodal admittance matrix to simulate the effect of changes in the passive elements of the network on the solution of a problem without changing the factorization.
Abstract: The compensation theorem is applied in conjunction with ordered triangular factorization of the nodal admittance matrix to simulate the effect of changes in the passive elements of the network on the solution of a problem without changing the factorization. The scheme includes network elements with mutual impedances. Compared with impedance matrix methods which are ordinarily used for power system applications, this method, which permits exploitation of matrix sparsity, always requires less computer storage and, with few exceptions, is much faster.
133Â citations
TL;DR: In this paper, a comprehensive computer-oriented procedure for probabilistic forecasting of hourly power-system loads with lead times of 1 to 24 hours is described, based on both historical load data and information from the latest weather forecast.
Abstract: A comprehensive computer-oriented procedure for Probablistic forecasting of hourly power-system loads with lead times of 1 to 24 hours is described. The forecasts produced are based on both historical load data and information from the latest weather forecast. The methodology combines stochastic load models and adaptive weather- load models optimally to yield an adaptive forecasting procedure especially suited for real-time control of power systems.
129Â citations
TL;DR: A hybrid Newton formulation exploiting the mathematical decoupling of busbar-voltage angle and magnitude calculations has advantages over the formal Newton approach in terms of computer storage and speed, particularly in adjusted solutions, and is at least as reliably convergent.
Abstract: In Newton load-flow solutions the mathematical decoupling of busbar-voltage angle and magnitude calculations has several computational and conceptual attractions. A hybrid Newton formulation exploiting this principle has been developed and well tested. For moderately-accurate solutions the method has advantages over the formal Newton approach in terms of computer storage and speed, particularly in adjusted solutions, and is at least as reliably convergent.
125Â citations
TL;DR: A fast approximate method is presented for solving the ac power flow problem for line and generator outages, significantly more accurate than any linear approximation and significantly faster than the Newton-Raphson method for an approximate solution.
Abstract: A fast approximate method is presented for solving the ac power flow problem for line and generator outages. The method is significantly more accurate than any linear approximation and significantly faster than the Newton-Raphson method for an approximate solution. The method has applications in system planning and operations where approximate ac power flow solutions are acceptable. The method is applicable to system planning for rapid location of design criteria violations and it is particularly well adapted for system operation use as an on-line security monitor. Efficiency is achieved through decoupling of real and reactive power equations, sparse matrix methods, an experimentally determined iteration scheme and the use of the matrix inversion lemma to simulate the effect of branch outages.
118Â citations
TL;DR: In this paper, the effects of turbine dynamics on the average system frequency behavior of a multi- generator system after a major generation loss or load change when the system remains in synchronism are modeled.
Abstract: This paper endeavors to model the effects of governor- turbine dynamics on the average system frequency behavior of a multi- generator system after a major generation loss or load change when the system remains in synchronism. The maximum frequency deviation and the time at which the maximum occurs are the main quantities of interest. Two independent concepts are presented to convert a closed-loop, high dimensional, nonlinear model into approximate, open-loop, low dimensional, linear ones (the delay and the canonical models). The delay model uses pure time delay to model "fast time constants" and valve motion and converts the closed loop model into an open loop one. The canonical model expresses the turbine reheats respo'nse as a linear combination of a set of "basis" functions and provides a basis for combining many machines into one simplified, low dimensional model. The two models can be implemented concurrently, to give a very large reduction in complexity when a multi-machine system is analyzed.
109Â citations
TL;DR: In this article, the authors defined a dimensionless stability margin which lies between one and zero (steady state in- stability) and is easily computed from a load flow, where the margin of torque is defined as the least change in power flows that will cause instability.
Abstract: The flow function of a power system is the vector of node powers expressed in terms of the node angles The Jacobian is the matrix of partial derivatives of the flow vector with respect to the angle vector The ratio of the determinant of the Jacobian to the value which it has when the node angles are set to zero is a dimensionless stability margin which lies between one and zero (steady-state in- stability) and is easily computed from a load flow The margin of torque is the least change in power flows that will cause instability Maximizing the torque margin or maximizing the stability margin with a load constraint yields the optimum dispatching change to maximize security
106Â citations
TL;DR: In this article, the relationship of electro-chemical and electrical trees found in service-aged cables is evaluated and two cable designs which have been shown to be particularly susceptible to electrochemical treeing and early failure are described.
Abstract: This paper is a continuation of the investigation reported previously1,2. The relationship of electro- chemical and electrical trees found in service-aged cables is evaluated. Additional observations and evaluations are made in light of new knowledge of electrochemical treeing including the use of a dyeing technique which affects the data previously reported. Two cable designs which have been shown to be particularly susceptible to electrochemical treeing and early failure are described.
TL;DR: In this paper, the commutation principle for HVDC circuit breakers is described whereby the current in the circuit is brought to zero by a bucking current from a precharged capacitor.
Abstract: The commutation principle for HVDC circuit breakers is described whereby the current in the circuit is brought to zero by a bucking current from a precharged capacitor. Circuit features are described to render this procedure easier for the interrupter and typical component requirements are discussed. The functions of current interruption and energy absorption should be separated; to this end, one type of surge suppressor is described. With breakers of this type, multi-terminal HVDC systems could be operated much like comparable AC systems, with only minimal dependence on terminal controls. A tapped line is given as an example.
TL;DR: In this article, the effects of conducting particles on breakdown in compressed SF6 under alternating voltage conditions were investigated with free particles of different shapes and materials compared with those obtained with fixed particles for both parallel-plane and coaxial electrode geometrics.
Abstract: This paper describes studies of the effects of conducting particles on breakdown phenomena in compressed SF6 under alternating voltage conditions. Results with free particles of different shapes and materials are compared with those obtained with fixed particles for both parallel-plane and coaxial electrode geometrics. Calculations of the particle motion and of the energy in microdischarges between particle and electrodes are used to suggest mechanisms by which breakdown is initiated. It is shown that the breakdown voltage, which can be as low as 10% of the uncontaminated value, is markedly dependent on particle shape, size and material, and that the nature of the motion in alternating fields is important in establishing conditions for free- particle-triggered breakdown.
TL;DR: In this article, the problem of designing a load frequency control law which reduces transient frequency oscillations (swings) and reduces the number of control signals sent to power houses is investigated.
Abstract: The problem of designing a load frequency control law which reduces transient frequency oscillations (swings) and reduces the number of control signals sent to power houses is investigated. A linear model of an area of an interconnected power system is developed, and a discrete time, linear-plus-deadband, feedback control law is designed. Feedback variables include cumulative inadvertent interchange, frequency deviation, integral of frequency deviation, real power absorbed by loads, and governor-turbine variables. This linear-plus-deadband control is an application of a special case of a more general "set-theoretic" class of control laws. A simulation of two areas with two hydro sources is presented. The dynamic response to a step load change is determined for the case of no load frequency control, load frequency control presently used by power companies, and load frequency control designed in this paper.
TL;DR: In this paper, an extension of Bergeron's Method of Characteristics that is applicable to the analysis of transmission lines with frequency dependent parameters is described, and the application to single phase and multiphase transposed lines is discussed with examples.
Abstract: This paper describes an extension of Bergeron's Method of Characteristics that is applicable to the analysis of transmission lines with frequency dependent parameters. This method can be inserted in existing general purpose programs that use Bergeron's Method. The application to single phase and multiphase transposed lines is discussed with examples and the theory is developed for multiphase untransposed lines.
TL;DR: In this article, the same capacity outage probability table as used in the loss-of-load probability method is used to determine the effective load-carrying capability of each unit to be scheduled.
Abstract: When scheduling generating units for maintenance one of the goals is to level the risks of capacity shortages throughout the year. Level reserves have been used as an indication of level risk. This paper illustrates that better schedules can be found by a method that uses effective capability in place of reserve. The five step method of incorporating risk considerations into existing maintenance scheduling procedures is described and illustrated. The same capacity outage probability table as used in the loss-of-load probability method is used to determine the effective load-carrying capability of each unit to be scheduled. These effective capabilities take the place of the unit ratings in the reserve leveling portion of existing procedures. The loads forecast for each maintenance period are also converted into an equivalent load which reflects the variability of peak loads during the period.
TL;DR: In this article, a counterexample is given for which two stable solutions exist, and an approach towards the analysis of uniqueness is presented that adds some insight into the nature of load-flow solutions in general.
Abstract: Practical experience with load-flow solutions has indicated that stable solutions are probably unique, given sufficient data about a network to determine a solution from the standpoint of dimensionality, i.e., having as many equations as variables for the remaining unknowns. A counterexample is given here for which two stable solutions exist, and an approach towards the analysis of uniqueness is presented that adds some insight into the nature of load-flow solutions in general.
TL;DR: In this paper, the center of angle is defined as the inertia weighted average of all rotor angles and the angular velocity of the centre of angle accurately describes the frequency of the system.
Abstract: The evaluation of the stability of a power system during a transient requires that the dynamics of the subsystems be decomposed into relative and collective motions. This decomposition must establish a distinction between synchronous and frequency equilibria. Such a decomposition is made possible by specifying a system center of angle which is defined as the inertia weighted average of all rotor angles. The angular velocity of the center of angle accurately describes the frequency of the system. An angular coordinate of each rotating element in the system can be specified relative to the center of angle. In terms of these coordinates a simple expression is obtained for the exact transient kinetic energy of the system. A transformation relating center of angle referenced variables to the usual one machine reference allows the simultaneous use of both references each where best suited.
TL;DR: In this paper, a procedure for determining the optimal plan for the expansion of the generation facilities of a power system over a long period of time is described, based on probabalistic simulation methods and an advanced dynamic programming formulation of the problem.
Abstract: The paper describes a procedure for determining the optimal plan for the expansion of the generation facilities of a power system over a long period of time. A method of production costing based on probabalistic simulation methods is combined with an advanced dynamic programming formulation of the problem in order to treat uncertainty in a systematic manner.
TL;DR: An experimental general-purpose process-control digital computer system provides high-speed phase-and ground-distance fault protection of one 230 kV transmission line and an automatic oscillograph and diagnostic programs will allow a study of field performance.
Abstract: An experimental general-purpose process-control digital computer system provides high-speed phase-and ground-distance fault protection of one 230 kV transmission line. The stored program performs all of the relaying functions using the output of an analog-to- digital converter which reads the instantaneous value of the power- system currents and voltages. Model line tests described in a companion paper (II -Test Results) form the basis for preliminary performance evaluation. An automatic oscillograph and diagnostic programs will allow a study of field performance.
TL;DR: This paper further describes this efficient method of computing the real-time load flow solution for a power system network and an efficient numerical solution technique particularly applicable to this problem is outlined.
Abstract: Extending the theoretical foundations established in Part I(1), this paper further describes this efficient method of computing the real-time load flow solution for a power system network. An efficient numerical solution technique particularly applicable to this problem is outlined. Relative weighting of the measurements is analyzed in terms of the measurement accuracies. A method is given for dynamic determination of the frequency of the state estimate calculations. The effects of real-time changes in the network are discussed.
TL;DR: The principles of a method of transformer protection by digital computer are described, which is essentially an adaptation ion of harmonic-restraint differential protection.
Abstract: The principles of a method of transformer protection by digital computer are described. The method is essentially an adaptation ion of harmonic-restraint differential protection.
TL;DR: In this paper, the optimal linear regulator design technique of determining the weighting matrix Q with dominant eigenvalue shift, developed in a companion paper, is applied to the optimal stabilization of a multi-machine system.
Abstract: The optimal linear regulator design technique of determining the weighting matrix Q with dominant eigenvalue shift, developed in a companion paper[6], is applied to the optimal stabilization of a multi- machine system. Two cases are studied, the first is with one optimal controller uE1 on one machine of the m-machine system and the other with m optimal controllers uEM for the m-machine system. For comparison arison a one optimal controller uE on one machine with the rest approximated as an infinite system and m optimal controllers of individual idual design are also investigated. Nonlinear tests are given. It is found that uEI control is better than uE control, uEM control is better still than UEI control, and individual uE controllers are not good for the overall system.
TL;DR: In this paper, the authors combine economic load allocation and supplementary control action into a single dynamic optimal control problem to overcome the disadvantages of static optimization techniques to solve the economic load assignment problem.
Abstract: Electric utilities presently use static optimization techniques to solve the economic load allocation problem. Experience has shown that a number of difficulties arise when these solutions are incorporated in the feedback control of dynamic electric power networks. This research attempts to overcome the disadvantages of such controllers by combining economic load allocation and supplementary control action into a single dynamic optimal control problem.
TL;DR: In this article, the optimal linear state regulator for load-frequency control is proposed for a power system, where the incremental power demand in the power system is not always apriori known, and direct application of the optimum linear-state regulator to load frequency control is not possible.
Abstract: Since the incremental power demand in a power system is not always apriori known, direct application of the optimum linear- state regulator to load-frequency control is not possible Furthermore, load-frequency control generally requires the use of an integral type control operation to meet the system operating specifications This requirement is introduced into the formulation of the optimum load- frequency control problem presented in this paper
TL;DR: In this paper, a procedure for locating directly the lowest saddle point of the potential energy function associated with a power transmission network is presented, which is used to compute a margin of stability that specifies the maximum asynchronous transient energy that can be retained by the system while in synchronism.
Abstract: A procedure for locating directly the lowest saddle point of the potential energy function associated with a power transmission network is presented. This procedure is used to compute a margin of stability that specifies the maximum asynchronous transient energy that can be retained by the system while in synchronism. The potential function is shown to be convex in the principal region of the angle space. A unique solution is shown to exist for the load flow problem if the algorithm of solution is initiated at the origin.
TL;DR: In this article, the authors explain two new theories of the linear induction motor, and indicate that the end effect exercises very adverse influence on motor performances, and propose the compensated linear induction motors as a measure to eliminate.
Abstract: The paper explains two new theories of the linear induction motor, and indicates that the end effect exercises very adverse influence on motor performances, and proposes the compensated linear induction motor as a measure to eliminate. the end effect.
TL;DR: In this paper, the relationship between remaining strength, time and temperature for conductors operated at elevated temperatures are presented as empirical models based on elevated temperature test results, and the comparison between the remaining strength predicted from the models and the measured remaining strength is shown.
Abstract: The relationships between "remaining strength", time and temperature for conductors operated at elevated temperatures are presented as empirical models based on elevated temperature test results. The comparison between the remaining strength predicted from the models and the measured remaining strength is shown. Use of the models is explained and examples of their use are presented.
TL;DR: The technique is a method for generating maintenance schedules which increase reliability and meet all practical scheduling constraints, and the program can be applied to the coordination of maintenance within power pools.
Abstract: As generating facilities increase in size, number and complexity, the impact of maintenance schedules on power system reliability and cost also increases. This paper describes a technique and a computer program which have been developed as an operating and planning tool for scheduling the maintenance of generating facilities. The technique is a method for generating maintenance schedules which increase reliability and meet all practical scheduling constraints. The paper includes a description of the maintenance scheduling problem, the model on which the scheduling technique is based, and a description of the optimization technique. The model used in the program can be applied to large systems and recognizes a comprehensive set of scheduling constraints, including the availability of crews, outdoor units, past and pre-scheduled maintenance, maintenance of auxiliary equipment and others. The maintenance of each unit is scheduled so that the interrelated constraints on the system are resolved and so that the minimum net reserve in the schedule is maximized. The approach and the program can also be applied to the coordination of maintenance within power pools. Program input and output are shown for the application of the program to a sample system.
TL;DR: The effectiveness of the commutation principle, using vacuum interrupters as a means for interrupting high direct current at high voltage, has been demonstrated convincingly by a large number of tests as discussed by the authors.
Abstract: The effectiveness of the commutation principle, using vacuum interrupters as a means for interrupting high direct current at high voltage, has been demonstrated convincingly by a large number of tests. Currents in excess of 15 kA at 20 kV have been interrupted by a single device in an inductive circuit. Tests are reported in which higher current were cleared by paralleling interrupters. Interrupters have been tested in series, indicating that the principle can be extended to high voltages. A high speed mechanism is described which was designed specifically for circuit breakers of this type. The necessary technology for producing HVDC circuit breakers appears to be at hand.