Showing papers on "Transient (oscillation) published in 1970"

Construction of minimal linear state-variable models from finite input-output data

Abstract: An algorithm for constructing minimal linear finite-dimensional realizations (a minimal partial realization) of an unknown (possibly infinite-dimensional) system from an external description as given by its Markov parameters is presented. It is shown that the resulting realization in essence models the transient response of the unknown system. If the unknown system is linear, this technique can be used to find a smaller dimensional linear system having the same transient characteristics. If the unknown system is nonlinear, the technique can be used either 1) to determine a useful nonlinear model, or 2) te determine a linear model, both of which approximate the transient response of the nonlinear system.

Transient scattering from conducting cylinders

Abstract: A method for determining the fields scattered by arbitrarily shaped cylindrical conducting structures with a transient incident wave is described. The transient scattering problem is reduced to the solution of a time domain integral equation which in turn is solved directly in the time domain by means of a digital computer. The approximate electromagnetic impulse response for a number of cylindrical scatterers is calculated using this method.

Improvement of Power System Transient Stability Using Optimal Control: Bang-Bang Control of Reactance

Abstract: The problem of restoring a power system to its initial steady state in minimum time after a transient disturbance is identified as a minimum time problem in optimal control theory. The optimal control obtained to achieve this objective, by use of Pontryagin's maximum principle, is bang-bang control of line reactance. The implementation of this scheme on a simple power system model is shown, along with numerical results.

Transient Overvoltage on a Bipolar HVDC Overhead Line Caused by DC Line Faults

Abstract: Digital programs are used to investigate the overvoltages induced in one pole of a bipolar HVDC overhead line, and caused by a line-ground fault on the other dc pole. Various digital tests are carried out, bearing in mind in particular the nature of dc line termination at the converter stations, which may include filter circuits and a surge capacitor. It is shown that the terminal that looks inductive to a wavefront coming from the dc line is undesirable because it would cause high overvoltages at the terminal of the unfaulted pole. It is also shown that in order to reduce the risk of developing a double-pole outage from a single-pole fault, it is desirable to do away with the surge capacitor, if a suitable dc lightning arrester can be designed. Tests are presented in stages to isolate the effects of fault resistance, grid control, and line resistance. Results also indicate the restraints to be put upon the dv/dt line fault detection in order to avoid operation of this protection in the unfaulted pole.

Ambient light level detector including transient suppression circuitry

Abstract: A circuit which includes a level detector circuit which is operated at two output levels, one level being indicative of a first ambient light condition and the second being indicative of another light condition, therebeing a timing circuit operated by the Schmitt trigger and an output circuit operated by the timing circuit after a predetermined delay to overcome transient and temporary changes in ambient light.

Selfheating and thermal runaway phenomena in semiconductor devices

Abstract: A unitary treatment of the stationary and transient selfheating of semiconductor devices is presented which allows an analytic approach to various problems related to the thermal runaway phenomenon.

Stability of synchronous machines with 2-axis excitation systems

Abstract: The paper describes analogue- and digital-computer studies of a synchronous machine with various 2-axis-excitation control systems. The steady-state and transient performances of the same machine are analysed, assuming different control schemes, such as rotor-angle control and asynchronised operation, and are compared with a conventional machine. The effects of damper windings, regulator time constants and stabilising circuits on the steady-state performance are shown by regulation curves. It is confirmed that the voltage-regulator loop gain has virtually no effect on steady-state stability, provided the winding with a.v.r. control is aligned with the flux axis by an angle regulator. The improved transient-stability limits obtained with high gains are shown. The fundamentally different transient behaviour of unregulated doubly excited and conventional synchronous machines is explained, and confirmed using accurate mathematical models of the machines. The method of `small oscillations? is applied to determine the speed stability of an asynchronised synchronous machine, and the transient performances of three different control schemes are compared in terms of swing curves and switching-time curves.

Transient Properties of an Infinite Cylindrical Antenna

Abstract: The field of a perfectly conducting, infinitely long, cylindrical antenna with a slice generator excited by a step-function voltage wave form is computed at several positions in space. For field points remote from the source, analytical simplifications are possible, and the case where the antenna is loaded with uniform resistance can then be treated. A simple formula for determining the generator voltage wave form required to radiate a specified far-field wave form is derived.

On the Reflection of Electromagnetic Pulses From the Ionosphere

Abstract: The reflection of a transient plane wave, from an ionospheric model with a linear electron-density profile, is considered. After a discussion of causality and physical realizability, the impulse response is calculated for the special case of no collisions. For this special case, it is shown that the wave form of the reflected wave has a smoothly rising initial portion that is followed by a slowly damped oscillatory portion which comprises the main signal.

A Method of Improving Power System Transient Stability Using Controllable Parameters

Abstract: Controllable parameters in a power system include generator terminal voltage, generator input power, and network admittances. These parameters can be controlled to damp mechanical rotor oscillation in the generators and thereby improve system transient stability. Explicit equations are derived for the control of these parameters to introduce damping uniformly throughout a large power system. These equations are derived on the basis of minimizing a positive definite error function. Decision functions are included which inhibit damping action when it leads to system instability. This method can be used to coordinate the application of locally based damping techniques.

Effects of Excitation, Turbine Energy Control, and Transmission on Transient Stability

Abstract: Transient stability problems become much more severe where the system design criteria is based on "stuck-breaker" fault clearing times, particularly where three-phase faults are used. Such a criterion is difficult and frequently impossible to meet with normal system design. Results of studies exploring the relative effect on transient stability limits of several options available to the system planner, including transmission strength, excitation system response, and early valving, are presented. Early valving appears to offer attractive stability improvement in those cases where such improvement is needed.

The effect on conversion of flow rate variations in a heterogeneous catalytic reactor

Abstract: The unsteady state behavior of a tubular heterogeneous catalytic reactor, in which significant adsorption effects occur, has been investigated theoretically and experimentally. Transient responses of conversion to step increases and decreases of flow rate as well as to periodic variations in flow rate are considered. A simplified procedure for anticipating gross effects in cyclic processes is suggested.

Liquid dispensing apparatus

Abstract: For a fluid dispensing system, control apparatus controls the output of the delivery nozzle such that a container is filled to a predetermined level relative to the nozzle without the level detection inaccuracy due to surge of fluid within the container. The control has a circuit in which a bi-stable device is coupled to a detector on the delivery nozzle which is caused to operate when the bi-stable device is in the set condition. Surge merely causes a transient switch to the re-set condition, whereas a given level of fluid relative to the nozzle maintains the re-set condition and terminates fluid flow. Provision for reduced flow between detection of surge and detection of the given level is accomplished through a sequencing circuit.

Transient and steady heat transfer in a conducting and radiating medium

Abstract: The transient and steady heat transfer in a conducting, emitting, and absorbing medium is analyzed according to the differential formulation. The differential equations are first transformed into integral equations and then solved by successive approximations. Great insight into the effect of absorption and emission on the temperature distribution is afforded by the calculation of radiation potential. The steady problem is briefly examined and discussed together with the transient problem. For small times emission is found negligibly small in comparison with absorption, whereas for large times it is important only in a thin layer near the hotter surface.

Transient Fields of Acoustic Radiators

Abstract: A set of short sketches is presented, giving an overview, unobscured by mathematical detail, of the literature on transient fields of acoustic radiators. Related papers are grouped together and interrelationships between results emphasized.

Plugging an Induction Motor

Abstract: Plug stopping a low-inertia squirrel-cage induction motor can provide a very quick stop, but the motor draws high peak currents from the power system and delivers high transient torques to the driven machinery. This engineering phenomena is well documented, yet the potential pitfalls of plugging applications are often not appreciated. The induction motor is so widely used in industry that a review of its plugging characteristics may be useful.

New Stability Measure for Multimachine Power Systems

Abstract: A new measure of the relative transient stability of a multimachine power system based on the Lyapunov stability theory is introduced. Techniques of sensitivity analysis are used to determine numerically the influence of variations or errors in the estimation of the system parameters on the transient stability of a power system. In particular, data is presented for an application of these ideas to a one machine infinite bus system.