Showing papers on "Transient (oscillation) published in 1981"

Probabilistic Assessment of Transient Stability in a Practical Multimachine System

Abstract: The application of probabilistic techniques in the quantitative evaluation of power system reliability is steadily increasing. Probability methods are being used extensively in the assessment of static adequacy. Their application to the evaluation of transient or dynamic phenomena has not yet, however, been widely utilized. The probabilistic nature of the transient stability problem and the inclusion of the probabilities associated with the initiating factors such as the type, location and clearance of faults in the analysis of a simple single machine-infinite bus system has been demonstrated in a recent paper.1 The present paper addresses the problem of transient stability analysis in a practical multimachine system from a probabilistic view-point. The basic concepts developed in Reference ! are applied to a simplified 33 bus model based on the Saskatchewan Power Corporation (SPC) system, to demonstrate the technique of considering the probabilities associated with the occurrence and clearance of faults. Transient stability indices for each line, for different types of faults and a single stability index for any fault are obtained. A single stability index for the overall system is evaluated for different fault types and amy fault using actual system outage statistics. The effect of fault clearing and reclosing times on the system stability is investigated for the most critical line in the system.

Transient Stability of a Multi-Machine Power System Part I: Investigation of System Trajectories

Abstract: Direct methods of transient stability analysis of a multi-machine power system, using a function describing the system's transient energy, are discussed. By examining the trajectory of the disturbed system, the following fundamental questions are dealt with: the concept of a controlling unstable equilibrium point (u.e.p.), the manner in which some generators tend to lose synchronism, and identifying-the energy directly responsible for system separation. Resolving these issues will substantially improve transient stability analysis by a direct method.

A Fundamental Concept for High Speed Relaying

Abstract: This paper describes a fundamental approach for detecting the direction to a power system fault within the first milliseconds following the fault inception. The method is based on a combined evaluation of the voltage and current deviations generated by the fault occurrence. Design considerations and test results based on numerical simulations and on a transient network analyser are presented. The method solves several problems occurring in conventional relaying and is suitable for use in ultra high speed protection systems which employ a fast telecommunication channel between the ends of the protected network

Precise source location of the anomalous 1979 March 5 gamma-ray transient.

Abstract: Refinements in the source direction analysis of the observations of the unusual 1979 March 5 gamma-ray transient are presented. The final results from the interplantary gamma-ray burst network produce a 0.1 arcmin/sup 2/ error box. It is nested inside the initially determined 2 arcmin/sup 2/ source region of Evans et al. that identified the supernova remnant N49 in the Large Magellanic Cloud as a possible source. This smaller source location is within both the optical and X-ray contours of N49 although not positioned at either contour center.

Experimental Study of Transient Ground Impedances

Abstract: This paper presents the results of an experimental investigation of the transient behavior of ground impedances. The results obtained were used to derive equivalent circuits. An analog model was constructed and satisfactory agreement with the theoretical analysis obtained.

Computation of A.C.-D.C. System Disturbances - Part I. Interactive Coordination of Generator and Convertor Transient Models

Abstract: In the presence of h.v.d.c. links the conventional quasi - steady state simulation of power system disturbances is not justifiable. This paper describes a realistic solution which combines the efficiency of single-phase multimachine transient stability analysis and the accuracy of detailed transient convertor simulation. Versatility and moderate computing requirements establish the proposed solution as a viable alternative to the use of analogue simulators.

Optimal Control of Damped Flexible Gyroscopic Systems

Abstract: An optimal control scheme for damped gyroscopic systems is presented. The procedure works with real quantities alone. The optimal control scheme is based on the concept of independent modal-space control, leading to a set of independent second-order matrix Riccati equations. The solution of such equations can be obtained with relative ease for both the steady-state and the transient case. Damping is shown to be beneficial, resulting in enhanced control with less control effort.

Transient electromagnetic response of a polarizable ground

Abstract: When a uniform ground has a conductivity which may be described by a Cole‐Cole relaxation model with a positive time constant, then the transient response of such a ground will show evidence of induced polarization (IP) effects. The IP effects cause the transient initially to decay quite rapidly and to reverse polarity. After this reversal the transient decays much more slowly, the decay at this stage being about the same rate as a nonpolarizable ground.

Transient Stability of a Multi-Machine Power System. Part II: Critical Transient Energy

Abstract: This paper deals with transient stability analysis of a multi-machine power system using direct methods based on the transient energy of the system when subjected to a large disturbance. The component of the transient energy that does not contribute to system separation is identified, and is corrected for in the computation of the critical transient energy at clearing. The technique is validated by computing critical clearing times for two test systems and comparing the results with those obtained by time solutions.

Internal combustion engine transient fuel control apparatus

Abstract: Transient fuel control apparatus for an above the throttle fuel injected internal combustion engine includes apparatus effective to measure the time rate of change of throttle position and periodically derive therefrom a first transient correction number, apparatus effective to generate a first order lag filtered induction passage pressure signal, apparatus effective to derive rate of change of the induction passage pressure relative to the filtered induction passage pressure signal and derived therefrom a second transient fuel correction number and apparatus effective to modify the fuel injected into the induction passage from the quantity normally injected during steady state engine operation by an amount derived from the arithmetic sum of the first and second transient fuel correction numbers. The first transient fuel correction number may be calibrated independently to correct for change in the fuel supply necessary due to immediate change in the air flow past the throttle with a change in throttle position; the second transient fuel correction number may be independently calibrated to correct fuel supply for the change necessary due to changes in fuel stored within the manifold under varying induction passage pressure. If the engine includes an idle air bypass passage with an idle air control valve therein, a third transient fuel correction number based on the time rate of change of idle air control valve position may be added to the other to transient fuel correction numbers.

Protection System Modelling in a Probabilistic Assessment of Transient Stability

Abstract: The application of probability methods in the evaluation of power system transient stability has been demonstrated in recent papers1-3. A probabilistic index for transient stability was developed which in addition to considering the random variations in the operating conditions, included the probabilistic aspects associated with the type, location and clearance of the system faults. It was realized during these studies that there was a need to develop stochastic models for the protection system behaviour which include the actual design aspects. The operational behaviour of the protection system is an important component in the high degree of security and service continuity associated with bulk power systems. This paper illustrates an approach used to model the protection system in the probabilistic assessment of transient stability. The probability density functions of the operating times associated with the components of the protection system such as relays, breakers, etc. are used in conjunction with the reliabilities of the main and back-up protection schemes to obtain the probability density functions of the fault clearing time for different fault locations. These density functions are used together with the critical fault clearing time for a given fault type and location to obtain a probabilities index for transient stability. A simple distance impedance protection system is used to illustrate the procedure. Continuous as well as discrete density functions for the operating times of the protection system components are used. This paper illustrates the basic probabilistic nature of the fault clearing phenomenon and its importance in transient stability assessment.

Transient Performance Analysis of Self-Controlled Synchronous Motors

Abstract: The transient performance of self-controlled synchronous motors which are used as variable speed motors in industries is analyzed considering two types of position sensor used in these motors. A set of equations valid for the transient state is first derived and represented in a block diagram. Based on these equations, mechanical and electrical transient responses of the motors in the case of a step change in input voltage are analyzed. It is shown that the transient responses differ remarkably depending on the type of position sensor used. The transient characteristics of margin angle of commutation of thyristors are then compared in detail with the steady-state ones. It is shown that the thyristors in the inverter are commutated more successfully in the transient state than in the steady state when compared at the same dc input current. Finally, the transient responses in the case of a step change in load torque are investigated.

A Nonlinear Circuit Model for Transmission Lines in Corona

Abstract: A phenomenological transmission line corona model is proposed in this paper which accommodates the diverse aspects of steady-state and transient power and energy losses and change in capacitance. Single phase line sections have been represented by a nonlinear model circuit which changes its state depending on the present and the previous values of the voltage. Propagation with corona is simulated by cascading identical model circuits and the nonlinear transmission line equations are solved by a finite difference method. The charge-potential characteristics of line sections and the nonlinear propagation characteristics of voltage surges computed numerically from our model conform with available experimental data in the literature.

Design criteria for laboratory measurements of low permeability rocks

Abstract: The advantages and limitations of two versions of the pulse technique for laboratory measurements of low permeabilities (10−16 to 10−24 m²) are discussed. The transient pulse technique developed by Brace et al. [1968] is the preferred method because of the ease of data reduction. The modified transient pulse technique developed by Trimmer et al. [1980] can be used when the assumptions inherent in the transient pulse technique are invalid. The systematic error associated with the transient pulse technique is a function of the ratio of the effective sample pore volume to the reservoir volumes. If this ratio is less than 0.25, then the error associated with the transient technique is less than 10%. The modified transient pulse technique does not suffer from this systematic error. Criteria are also presented for optimizing the experimental configuration for measurement durations as well as ease of data reduction.

Wrong-way behavior of packed-bed reactors: 1. The pseudo-homogeneous model

Abstract: A sudden reduction in the feed temperature to a packed-bed reactor leads to a transient temperature rise, which is referred to as the wrong-way behavior. A pseudo-homogeneous plug-flow model is used to analyze the structure of this transient behavior. The key parameters which determine the magnitude of this response are the dimensionless adiabatic temperature rise, activation energy, heat transfer capacity, coolant temperature, magnitude of temperature drop and length of the reactor. A simple expression is derived for predicing the maximum transient temperature rise.

Isothermal Capacitance Transient Spectroscopy

Abstract: A new measurement method for deep levels in semiconductors is demonstrated, by which the measurement of the transient change of capacitance is performed under an isothermal condition (Isothermal Capacitance Transient Spectroscopy). The method allows us to construct a precise measurement and analysis system by a programmable calculator. Detailed experiment and analysis by the method in the case of Au-doped Si in dicate that the method is one of useful tools for spectroscopic analysis of deep levels in semiconductors.

Transient stability analysis of multimachine power system by Lyapunov's direct method

Abstract: Practical applications of Lyapunov's direct method to transient stability analyses of multimachine power systems have been obstructed by the well-known conservative nature and the computational difficulty accompanying the usual critical value of Lyapunov function. These problems have been solved in this paper by introducing a new critical value for the first swing stability, and by developing a efficient method of calculating it as well as one of taking account of transfer conductances. These methods have been applied to a transient stability analysis of a 10-machine power system, and yielded results of practical significance.

Power control for cooking appliance with transient operating modes

Abstract: A power control system for a heating element in a cooking appliance having a plurality of possible power settings which provides transient Fast-Heat and Fast-Cool operating modes initiated in response to user-initiated changes to higher or lower appliance power settings, respectively, to reduce the response required for the heating element temperature to reach the operating temperature associated with the new power setting Approximate heating element temperature information is provided to the control system by an energy counter which is incremented at a rate which is approximately proportional to the rate of increase of the heating element when energized at the power level being implemented This information is used to prevent initiation of a transient mode if the temperature of the element when the change in setting is made is such that operation in that mode is likely to overshoot the desired new operating temperature