Showing papers on "Electric power system published in 1973"

Solar-Induced-Currents in Power Systems: Cause and Effects

Abstract: This paper summarizes a research effort investigating the effects of geomagnetic storms on electric power systems. Geomagnetic storms, which are caused by solar flares, can cause spurious quasi-dc currents in power systems; these are termed solar-induced-currents (SIC). A summary of SIC data recorded on over 30 power systems across the United States is presented, and power system effects are discussed. The important problem of internal localized heating in power transformers due to SIC is presented, as well as a consideration of possible methods of mitigation of the SIC.

Automatic Power System Network Topology Determination

Abstract: The determination of power system network topology for off-line studies is a relatively simple problem since one-line diagrams inherently describe system configuration. In real time environments, system configuration is dynamic. Breakers may operate at any time producing some of the following effects: 1) circuits may or may not be disconnected, 2) substations may or may not separate possibly forming new nodes, thus varying the total number of nodes in a system, and 3) an interconnected system may split into several separated areas. Unless provisions are made to automatically incorporate in real time the effects of breaker operations on system topology, any calculation and decision based on a wrong configuration would be dangerous, especially when most needed: immediately after the occurrence of the abnormality ity which lead to breaker operations.

Method of effecting fast turbine valving for improvement of power system stability

Abstract: As an improved way of effecting fast valving of turbines of power system steam-electric generating units for the purpose of improving the stability of power transmission over transmission circuits to which their generators make connection .Iadd., .Iaddend.when stability is threatened by line faults and certain other stability endangering events, and in which intercept valves are rapidly closed on a momentary basis, the procedure of intercept valve closure is supplemented by simultaneously initiating turbine and steam supply source control programs, which (a) .[.being.]. .Iadd.bring .Iaddend.into effect a sustained reduction in turbine driving power via employment of measures which may include full closing of some or all control valves and/or employment of preprogrammed control valve repositioning, with provision to automatically divert high pressure steam to the condenser or to atmosphere as a way to prevent discharge of steam through high pressure safety valves. (b) bring into effect a rapidly executed process of reduction of rate of generation of steam within steam supply sources, and (c) initiate a control program that effects a predetermined degree of partial reopening of intercept valves early in the course of the generator rotor's first backward swing, following which intercept valves are further opened and control valve positions optionally revised in preprogrammed ways with the overall effect that in the period following the first forward swing the magnitude of turbine driving power is caused to hold below the value that applied prior to the event that initiated fast valving and to at most only briefly exceed a final sustained value that can be preset.

Hybrid power system

Abstract: A hybrid power system for a motor vehicle, comprising a prime mover such as an internal combustion engine and a flywheel which is driven from the prime mover when an excess of power output is available from the prime mover and which is in driving connection to a transmission input shaft when the vehicle is to be driven under heavy load. The flywheel is selectively connected to or disconnected from the prime mover and/or the transmission input shaft in accordance with schedules which are dictated by an electric control unit responsive to various operational variables of the vehicle. The power system may be so arranged as to drive the engine when the engine is to be started.

Effects of Synchronous Machine Modeling in Large Scale System Studies

Abstract: A study was made of the accuracy of utility power system stability simulations, as affected by the complexity of the synchronous generator models and the data used with the models. The investigation was performed by simulating the operation of a representative multimachine power system with many combinations of disturbance, initial load, system stiffness, model detail and model data. The findings from this study provide guidelines for the selection of the simplest computational machine models for use in large scale stability analyses, with the goal of minimizing the cost of computer usage while assuring sufficient accuracy of the results. Recommendations are made for selecting machine data more suitable for use in stability studies than the standard machine data.

Dynamic Models of Turbine Generators Derived From Solid Rotor Equivalent Circuits

Abstract: A method is described for determining the structure and coefficients of dynamic models of turbogenerators from detailed equivalent circuits of the d-and q-axes of a solid rotor generator. These models are intended for analyses of power system dynamics in cases where it is desirable to have a very accurate representation of the synchronous machine. The models have been used to study power system hunting or dynamic stability, first swing or transient stability, load rejection overvoltages, resynchronization of cross-compound turbine-generator sets, field current and voltage during out-of-step operation, voltage dip and other phenomena associated with machine operation on power systems. The paper reviews some of the experience obtained in system studies and in comparisons between test results and computer simulations.

Power-system load representation

Abstract: The paper concerns the representation of distributed loads of mixed but known composition. A general load model is employed which relates relative changes in active-and reactive-load demand to relative changes in applied voltage and frequency in terms of a set of four characteristic parameters. The object is to identify analytically the resultant characteristic parameters at a principal load busbar, taking into account the effects of feeders and distribution transformers as well as load composition. The analysis may start at any network level where load characteristics are known. An example is given, illustrating the application of the method.

Simultaneous Power Interchange Capability Analysis

Abstract: A procedure has been developed to determine the maximum simultaneous power interchange capability into a company (area) from its neighboring companies. The optimal combination of scheduled transfers with the neighbors to provide the maximum import is determined. The procedure identifies the outages and the facilities which limit the transfers. The new Interchange Capability Program (INCHCAP) developed at Commonwealth Edison Company and the optimizing technique f Linear Programming are used. Both transmission and generation limitations are considered.

A Dynamic Programming Model for the Expansion of Electric Power Systems

Abstract: This paper describes a dynamic programming model that has been developed to determine an optimal expansion plan for the generating capacity of an electric power system. The optimization model determines the least-cost mix of capacity between hydro, nuclear, thermal and peaking turbine plants, the size of the plants to add to the system, and the timing of these additions. We show how the computational requirements of this four-state-variable, four-decision-variable problem can be substantially reduced, resulting in a computationally feasible model. The techniques developed are applicable to a large class of capital budgeting problems under uncertainty. Reference is also made to the actual application of the model and an example is presented.

An Electric Drive

Abstract: The report describes an invention that is one of the family of AC electric drives permitting a broad range of control of the power of actuating mechanisms with blower-type change of drag torque, e.g., in ship electric power systems, in powerful fan and pump units, etc.

The optimal decentralized control of a power system consisting of a number of interconnected synchronous machines

Abstract: The optimal output decentralized (i.e. local) and global control of a power system consisting of three interconnected synchronous machines is considered in this paper. A computational method is introduced which enables the optimal output control (either global or local) of a complete system to be found, thereby allowing realistic control configurations to be studied.

Application of Pattern Recognition to Steady-State Security Evaluation in a Power System

Abstract: Power system operation is outlined and system security is defined. The need for security evaluation in power system operation is discussed, and the evaluation is presented as a pattern recognition problem. A suitable straightforward and quick procedure is used to select a small number of variables as features from a large set of variables which are normally available in power systems. Comparison is made on the security classification performances of a number of different types ot classifiers. The training of classifiers is carried out by a search algorithm which seeks to minimize the number of classification errors. The procedure to determine the security functions (classifiers) is illustrated by an example, and simulation results on the steady-state security of the CIGRE 225-kV system show that the pattern recognition approach to security evaluation is encouraging. Some uses of security functions in the control and operation of power systems are outlined. The effect of many of these uses cannot be achieved as easily by other existing methods. Finally, some of the problems associated with the application of pattern recognition to power system security evaluation are discussed.

Reliability Evaluation of Transmission Systems with Switching After Faults Approximations and a Computer Program

Abstract: Approximation methods and a computer program are presented, to facilitate the reliability evaluation of large power systems The approximations are based on an extension of the minimal-cut approach for computing reliability, to cover models that can account for switching after faults The program can select the required "minimal-cut" failure states through an analysis of the failure effects in every state, and calculate the overall system reliability indices, if certain system failure criterial apply

Multivoltage, regulated power supply with fault protection

Abstract: A power supply for providing a plurality of regulated voltage levels while protecting the power supply from damage due to fault conditions. The power supply provides apparatus for rectifying AC input power and, by means of a DC to DC converter, supplies a DC voltages to the output terminals.

Improvement of power-system transient stability by phase-shift insertion

Abstract: Computational studies of the transient stability of a synchronous machine connected to an infinite busbar by a double-circuit transmission line are used to illustrate the effect of relative phase-shift insertion between the machine and its associated power system. This method of obtaining a change in the effective rotor-excitation angle, and thereby the power transfer, is described, together with an outline of possible methods of implementation by a phase-shifting transformer in a power system.

Influence of Third Harmonic Circulating Currents in Selecting Neutral Grounding Devices

Abstract: It has long been recognized that third harmonic currents can and often do appear in the neutral of industrial generators. This paper will review the causes of such currents and the effects these currents have in the power system. The common methods of neutral grounding will be discussed with regard to circulating harmonic currents.

Lubricating and sealing system for a rotary power plant

Abstract: In a power system including a shaft driven by expanding a working fluid in a turboexpander and a housing surrounding the shaft and the rotor of the turboexpander, a seal is provided between a process zone containing the rotor and a lubricant zone by injecting a seal fluid into the housing between the two zones at a relatively high pressure. The seal fluid is preferably comprised of the lightest constituent of the working fluid, and the system includes means for recovering the seal fluid from the lubricant and from the working fluid and recycling it.

Real and Reactive Power Optimization by Suboptimum Techniques

Abstract: The short-term real and reactive power optimization of a large system is a non-linear programming problem and its solution requires a considerable amount of computational effort. In actual practice separate real and reactive power suboptimization techniques may be more suitable than a complete optimization(1). The results obtained by the suboptimal techniques under ideal conditions coincide with those from a real and reactive power optimization. In this paper, complete real and reactive optimization has been solved by suboptimization techniques. The proposed approach decomposes the complete problem into two halves, i. e. the optimum voltage evaluation and the real power optimization with optimally determined voltages. A theoretical treatment of the technique along with a qualitative and analytical discussion is provided. The method is applied to a small system and the results obtained are compared with a real and reactive power optimization.

Gas turbine power plant control apparatus including a turbine load control system

Abstract: A gas turbine power plant is provided with an industrial gas turbine which drives a generator coupled to a power system through a breaker. The turbine-generator plant is operated by a hybrid control system having digital function capability during sequenced startup, synchronizing, load buildup and steady state load, and shutdown operations. The control system also contains monitoring and protective subsystems which function through all stages of operation, with redundancy and permissive features which maximize turbine availability.

A Sensitivity Analysis of Weighted Least Squares State Estimation for Power Systems

Abstract: This study considers the effect of modeling errors upon the real-time calculation of the bus voltages (or static state) of an electric power system. A criterion for evaluating the sensitivity of weighted least squares state estimation is developed, and the method is applied to a simulated model of an actual transmission system. The mathematical aspects of the analysis are discussed, and the experimental results indicate the effects of errors in several types of system parameters.

Primary power fault detector

Abstract: Data processing and computer systems require continuous monitoring of the primary alternating current power. A power failure must be detected very quickly (within a fraction of a cycle), so that the contents of a volatile memory can be quickly converted into a nonvolatile form. This must occur before power system storage is expended and control is lost. RMS power direction is developed by the product of voltage and current with an integrated circuit multiplier device. When power fails, the circuit indicates a power flow reversal or power equals zero from the detected system current times voltage factor. A retriggerable one-shot in conjunction with a NAND gate is utilized to detect the instantaneous voltage drop to zero and current reversal in order to energize other circuits to protect such volatile data in the event of a power failure.

Three-phase power disturbance monitor

Abstract: A three-phase power disturbance monitor for sensing and recording anomalies occurring in electrical power systems which cause operational malfunctions in, and damage to, critical loads such as computers and synchronous communication equipment. The system senses and counts over and under voltage conditions, over and under frequency variations, and high or low threshold pulse transients. The monitor provides visual and audio warnings of power supply conditions which could damage equipment if left uncorrected for a period of time. The number of disturbances exceeding certain values is displayed on a digital counter. The monitor is equipped with a common input voltage section, a common 24 volt d.c. power supply and a front panel a.c. volt meter. Upper and lower threshold values for each condition are adjustable between certain limits determined from particular applications of the monitor. The audio and visual warning systems remain on if the disturbance continues to exceed a predetermined value for length of time. An external voltage feature has the capability of triggering a remote alarm system, powering down critical equipment and initiating the switching of critical loads to another power source.

On Lyapunov functions for power systems with transfer conductances

Abstract: The problem of a two-machine power system for stability studies is formulated, taking into consideration the transfer conductances in the transmission network. Lyapunov function is then obtained using a generalization of Popov's criterion due to Anderson.

Digital Control Scheme for a Generating Unit

Abstract: Computer applications in power systems have tended to evolve at the supervisory levels in system operation. Controls at the generation levels remain primarily an analog domain. To make the entire system operation flexible it is essential that the control devices be compatible. This points towards the application of computers as dedicated direct digital controllers at the primary control levels. This paper describes the development of an integrated and compatible scheme for complete digital control of a generating unit. The overall concept and details of a physical model being built to test the proposed control scheme are given.

Remotely monitored and controlled transformer

Abstract: A power transformer adapted for remote monitoring and controlling, and system of providing same. The transformer contains a temperature sensor, a pressure sensor, and a deenergizing switch. Electrical signals from the sensors are transferred to a remote load management center which compares the signals to predetermined standards and originates a switching signal when a standard is exceeded. The switching signal opens the switch to de-energize the transformer. The load management center may utilize standards which are fixed or which are variable with other conditions in the power system.

Gas turbine power plant control apparatus including a temperature reset starting control system and an ignition pressure control system

Abstract: A gas turbine power plant is provided with an industrial gas turbine which drives a generator coupled to a power system through a breaker. The turbine-generator plant is operated by a hybrid control system having digital function capability during sequenced startup, synchronizing, load buildup and steady state load, and shutdown operations. The control system also contains monitoring and protective subsystems which function through all stages of operation, with redundancy and permissive features which maximize turbine availability.

Aspects of Multiple Infeed of HVDC Inverter Stations into a Common A.C. System

Abstract: The question of possible limits of HVDC power supplied to an a.c. system is discussed on a general basis. This limit will be of interest, if a.c. systems are to be reinforced without increasing their short circuit capacity. The two important aspects, i.e. power frequency and harmonic phenomena are discussed in view of investigations on single HVDC converters published earlier by other authors. The results are extended to multiple infeed. It is shown that in contradiction to the general opinion at present, the short circuit ratio presents no limit to the rating of a single converter station, that for multiple infeed each station can be dealt with separately with regard to its rating and that increasing the number of inverter stations connected to the same system does not increase the danger of harmonic instability.