Models Of Power System Components Research Articles

An improved reliability model for redundant protective systems-Markov models

A number of reliability models of power system components including protective-system failures have been proposed. These models have concentrated on modeling a single protective device. When this protections fails, it is usually assumed that backup protection will isolate the faulted component with 100% reliability. In reality, power system components, have redundant protection schemes with two or more protective devices operating in parallel. Existing reliability models have not dealt with redundant protective systems adequately. This paper presents an improved reliability model capable of modeling these systems. The proposed Markov model and the equations for a number of important performance indices are derived and illustrated in this paper using the data for a typical transmission system.

Parallel simulation of industrial power system transients by an inherent parallel algorithm

An inherent parallel algorithm for simulating industrial power system transient characteristics is implemented. This algorithm is based on the waveform relaxation method (WRM). The component connection model (CCM) is applied to assemble the individual power system component models into an integrated system representation, among which the generator stator and network transients are taken into account. Moreover, four different schemes of the relaxation Newton iteration method can be used to solve these separated component equation sets concurrently. To demonstrate the effectiveness of the proposed algorithm, the IEEE second benchmark model system No. 2 and a practical industrial cogeneration system are selected for numerical illustrations. The satisfactory speedups with different concurrent and vectorized numerical realizations on both the Alliant FX/80 and the Convex C3840 multi-processor systems are also provided. Results obtained from these simulations indicate that this combined algorithm is suitable for detailed industrial power system transient analysis and multiprocessor parallel processing.

Eigen analysis of series compensation schemes reducing the potential of subsynchronous resonance

A.A. Edris (see ibid., vol.5, no.1, p.219-36, 1990) described a new concept for mitigation of the phenomenon of subsynchronous resonance (SSR) based on asymmetrical series capacitor compensation at SSR frequencies. The studies reported by A.A. Edris are based on a digital time-domain simulation technique. This paper provides a quantitative evaluation of the concept using a novel eigen analysis approach. The eigen analysis approach represents the mathematical models of power system components in the three-phase basis, and can evaluate the impacts of asymmetry and imbalance on the system dynamics in the subsynchronous frequency range. The study results restate the technical feasibility of the proposed SSR countermeasure. This paper opens the avenue for examination of active power filter topologies to introduce artificial asymmetry at SSR frequencies to counteract torsional oscillations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A New Approach to Calculate the Decaying AC Contributions to Short Circuit: The "Characteristic" Currents Method

For the near to generator short-circuit analysis, it is well known that a rigorous calculation procedure requires the use of complex dynamic models of power system components. In most practical cases, however, it is sufficient to adopt simplified and standard based calculation methods. For these cases the paper suggests a new approach of the short-circuit models of power system components based on the characteristic currents method [l]. The paper, at first, presents a short overview of the IEC Standard 909, assumed as reference for the proposed approach. The calculation assumptions and the simplifications of the IEC Standard are pointed out in order to evidence how the new approach proposed allows to obtain conservative, but more accurate results. The characteristic currents procedure is successively applied to a sample network with external feeder and internal generation and with motor load. The same network is analyzed by means of the IEC procedure and by means of a computer program able to consider dynamic models of electrical equipment. A comparison among these approaches is carried out in order to validate the characteristic currents method. Comparisons between the proposed method and recognized IEEE/ANSI standards have not been performed in the paper.

A general simulation algorithm for the accurate assessment of isolated diesel-wind turbines systems interaction. Part II: Implementation of the algorithm and case-studies with induction generators

In the second part of this two-part paper, a general algorithm to simulate and assess the dynamic behavior of any isolated diesel-wind turbine power system is analyzed and implemented. It is presented how the various power system and wind energy conversion system (WECS) component models described in detail in Part I of the paper can be implemented in order to create integrated simulation software. Case studies for the small size isolated power system on the French island of Desirade are given and analyzed. The algorithm is validated and its usefulness to determine the wind energy penetration level at any disturbed operation conditions is demonstrated. >

Verification of the electromechanical transients program setpos by means of comprehensive power‐station measurements

AbstractMost electrical power engineers involved with the planning and designing of power station auxiliary power supply systems are faced with the problem of credibility of the electromechanical transients programs offered as supplementary aid in fulfilling their jobs. These programs contain a variety of mathematical models of electrical power system components, which can be combined to constitute the electrical system being analysed. Most simulation programs have been tested on a number of theoretical cases and the results compared to those of other similar computer programs. This is due to the general lack of‐ and difficulties in achieving ‐ field measurements of reproducible electromechanical transients in fully known power subsystems. Such field measurements of a slow busbar switching in the auxiliary system of a modern power station unit are presented and compared to the computational results obtained by simulating the incident using the SETPOS electromechanical transients program.

Running EMTP on PCs (power systems)

The Electromagnetic Transients Program (EMTP) is a computer program for the simulation of electric power system transient phenomena. The program provides a large set of device models permitting accurate modeling of power system components over a wide frequency range. Traditionally, this program has existed only in mainframe and minicomputer environments, limiting its use to engineers and companies with access to these facilities. Recently, the EMTP has been made available for use on IBM and compatible personal computers using the IBM OS/2 and Microsoft Windows operating systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Incorporation of SVCs into energy function methods

The incorporation of static VAr compensators (SVCs) into energy function methods is described. The consequences of SVCs encountering limits are of particular interest. At a limit point, the network description undergoes a change. System behavior is not smooth. This lack of smoothness is investigated. A valid energy function, which includes the effects of SVCs and their limits, is established. Stability assessment results, obtained for a real power system, demonstrate the effects of SVC limits. It is shown that the theory developed for handling limits can be applied to models of other power system components.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reliability Modelling in Systems with Non-Exponential Down Time Distributions

There has been considerable work done in the past few years on the development and analysis of reliability models for power system components, subsystems and systems1. The most well known models are probably those which have evolved in the development of reliability techniques in the capacity planning area. The basic concepts of state probabilities and the frequencies associated with state encounters have also been successfully applied in subsystem and integrated system aanalysis2,3. State transition diagrams have been utilized to analyze the benefits or penalties associated with different step-up transformer arrangements for a large generating unit4. The modelling techniques illustrated in these applications are not vastly different and the solutions were obtained by considering the system as a conventional Markov process.