Showing papers on "Power-flow study published in 1975"

Stochastic load flows

Abstract: The load flow study has been at the center of studies made for designing and operating power systems for many years. It is well known that forecasted data used in load flow studies contain errors that affect the solution, as can be evidenced by running many cases perturbing the input data. This paper presents a method for calculating the effect of the propagation of data inaccuracies through the load flow calculations, thus obtaining a range of values for each output quantity that, to a high degree of probability, encloses the operating conditions of the system. The method is efficient and can be added to any existing load flow program. Results of cases run on the AEP system are included.

Solution of Large Networks by Matrix Methods

Abstract: General Background Matrix Algebra Extensions of the Z-Matrix Short-Circuit Program to Include Very Large Systems Single-Phase Short Circuits State-Estimation Load Flow Solutions The Economics of Operating a Power System Optimum Load Flow Transient Stability High-Speed Reduced-Accuracy Power Flow Calculations for Contingency Evaluation and Maximum Interchange Capability Determinations Appendixes Index.

A new power flow model and solution methodߞIncluding load and generator characteristics and effects of system control devices

Abstract: A new power flow model has been developed for the steady state behavior of large complex power systems, it allows the study of power flow under abnormal conditions as well as normal conditions. It is also shown how Newton's method can be efficiently applied to the model to provide exact and practicable solutions for a new steady state following the disturbance. Advanced applications are introduced which show how the steady state model can be combined with a dynamic simulation program.

Power stabilizer design using root locus methods

Abstract: This paper describes a different approach to the design of power stabilizers for damping out tie-line power oscillations in power systems. The technique described in this paper was successfully applied at a generating station of the Saskatchewan Power Corporation System with the results from these tests included in the latter part of this paper. The technique can be applied directly to systems characterized by lightly damped oscillations and gives an explicit indication of the amount of improvement in system damping for different combinations of power stabilizer parameters. This procedure allows for a graphical approach to the design of power stabilizers and serves as a synthesis procedure when the design constraints are relaxed so that the speed stabilizer is required to provide an improvement in system damping.

Series capacitors in power systems

Abstract: The paper reviews the experience obtained with series-compensated power systems, particularly in Sweden, where internally fused capacitor units and simple system designs have contributed to the the good results. It also introduces new approaches for meeting future demands, e.g., optronic protection and a high-speed flip-flop reinsertion system.

Effects of voltage and reactive power constraints on power system reliability

Abstract: The paper deals with a method for the reliability evaluation of a power generation and transmission system, when considering, together with the constraints on the active power capability of elements, the voltage constraint in network nodes. The approach suggested is an extension of a previous method for the reliability evaluation when considering only the active power capability constraints. The method is based on the approximate evaluation, by means of linear computation methods, of the reactive power flows and of the consequent voltage values in network nodes. This evaluation is performed starting from the approximate evaluation of the active power flow derived with the classic method of d.c. load-flow computation. The system performance, as a consequence of voltage constraints, is quantitatively evaluated by means of two indices: the first being the power disconnected in the nodes as a consequence of unacceptable voltage values or lack of reactive generation, the second being the irregularity of the voltage Service.

System requirements for dynamic performance and response of generating units

Abstract: Starting from a discussion of the fundamental characteristics of modern interconnected power systems, this paper goes on to categorize requirements for dynamic performance and response imposed on the aggregate generation which supplies the system. Both normal and abnormal operating modes are considered. The performance and response requirements are shown to stem from basic needs to maintain voltage, frequency, time, and continuity of service as well as the secondary requirements of maintaining operating economies and controlling inadvertent interchange between neighboring power systems. Typical data taken from operating records are used to illustrate and quantify several of the response requirements.

Use of digital computer simulations to assess long-term power system dynamic response

Abstract: This paper describes the uses of a digital computer program developed to simulate the long-term dynamics of bulk power systems. Power system long-term dynamics, including effects dominant in the period extending for several minutes, often determine whether a power system will successfully avoid cascading failure following a major disturbance. The paper describes the simulation of an evolving disturbance on a hypothetical power system using both a conventional short-term simulation program and a new long-term simulation program. Results for three measures devised to modify the system capability to withstand the disturbance are included.

Interconnection modelling of power systems

Abstract: Mathematical models are required to calculate tie flows for allocating generation among groups of interconnected companies, for costing and cost reconstruction of power interchanges between companies or pools, and for a variety of security functions. This paper presents new procedures for modelling the many ties between groups of interconnected power companies. The systems whose interconnections are modelled can represent one pool or a multiplicity of power pools, typical of U. S. systems. Novel procedures of constructing the interconnection models are described, including the automatic formation of topological matrices which define the circulating and interchange paths existing in the interconnections. The models can be used in both off-line studies and in real time operations of power systems. Results are represented verifying the development.

An approach for preventing system insecurities arising from line and transformer outages

Abstract: This paper presents an algorithm that improves steady state security of a power system. An objective function which includes power flows in the overloaded system elements and bus voltages that exceed the permissible limits is formulated. Weighting factors, obtained from the magnitudes and frequencies of the violations, are also used in this function. An optimal combination of controlling variables, such as voltage magnitudes at generator buses, real power generation, transformer and phase shifter tap settings, is determined by minimizing the objective function. Instead of the non-linear load flow equations, sensitivity analysis approach has been used to reduce computation time and effort. This technique has been applied to a 6 bus model and a 26 bus version of the Saskatchewan Power Corporation transmission system; and some of the more interesting results are presented.

Algorithms for Solving Reliability Models of Systems Exposed to a 2-State Environment

Abstract: An algorithm is described for solving the reliability model of a repairable system of n identical components placed in a fluctuating 2-state environment. An important application is where the effects of alternating normal and severe weather conditions are to be evaluated. A modified version of the algorithm can accommodate the case where faults are followed by switching operations, as in power transmission networks. Whereas the standard Markov method to solve such models is cumbersome and other available methods are often limited in scope, the proposed algorithm is fast, reasonably accurate, and does not require a computer.

A simulation technique for studying real and reactive power flow patterns

Abstract: This paper presents a technique that simulates dispatch actions, such as, changing transformer and phase shifter tap settings and changing voltage magnitudes at voltage controlled buses in a power system. The changes of power injection at one or two system buses, which would simulate the required dispatch action, are calculated using the sensitivity matrix of the basic system state. The real and reactive power flowing in all the system elements and voltages at all the system buses are then computed. The proposed technique has been applied to the interconnected Saskatchewan Power Corporation and Manitoba Hydro systems and to the 118 bus IEEE test system. The power flows and bus voltages calculated by the proposed technique are compared with those obtained from the Newton Raphson load flows.

Analysis of Large Power Systems

Abstract: Computer-oriented power systems analysis procedures in the electric utilities are surveyed The growth of electric power systems is discussed along with the solution of sparse network equations, power flow, and stability studies

An Analytical Examination of Impedance and Signal Power Levels Along a Multiplex Data Bus

Abstract: : Using MIL-STD-1553 (USAF) as a guide in defining a Multiplex Data Bus, this paper presents in graphical form the results of a series of calculations to determine bus impedance, stub impedance, and signal power levels along a Multiplex Data Bus The paper also discusses the significance of these parameters in MUX Bus operation

A New Approach to Modelling in Planning of Electric Power Systems

Abstract: The Paper shows the structure of a planning concept for electricity supply systems which, although developed for the Austrian system, is applicable on a general basis to other, more extensive, environmental systems.

A Multi- Area Approach to the Economic Optimization of Electric Power System

Abstract: In this paper, the problem of short-term economic dispatch of active power in a combined hydro-thermal electric power system is considered The problem studied is a 24 hours optimization, with operational cost as associated criterion It is assumed that consumer's demand, defined as a number of time functions, as well as technical constraints concerning power production units, and transmission line capabilities are satisfied within the period of optimization The deterministic time discrete mathematical model of the above stated problem consists of a set of nonlinear algebraic equations and a set of nonequalities The power system is decomposed into a number of interconnected power areas Consequently, a number of local less dimensional area optimization subproblems are defined Each of them is a typical nonlinear programming problem Coordination among subproblem solutions is performed by a higher level decision making effort It is done by specially derrived coordination algorithm