Grega Bizjak

Circuit breaker model for digital simulation based on Mayr's and Cassie's differential arc equations

A model of a circuit breaker for digital simulation programs based on the Mayrs and Cassies differential arc equations was developed. The model can be used to determine the current interruption capability of the circuit breaker. The theoretical basis and the structure of the model are described. The model is verified on a sample of measured results, and the use of the model for practical application is demonstrated. Although the validation of the model is limited to the vicinity of current zero, it can be usefully used. Its advantage lies in the fact that the simulation programs set and solve the system of breaker and network differential equations. Calculation of a breaker capability can so be done using a complex network. >

Combined model of SF/sub 6/ circuit breaker for use in digital simulation programs

The paper describes a combined model of the high-voltage SF/sub 6/ circuit breaker for digital simulations. The model is intended for detailed simulations of switching transients in electrical power systems in cases where interaction between physical phenomena in the circuit breaker and the system plays important role. The circuit breaker model is a black-box model introduced in the modeled system as a two-pole element with a variable impedance. The value of impedance is determined by a regulator dependent on a mathematical model. It consists of four partial models: a closed circuit-breaker model, a burning arc model, a current zero crossing model, and an open circuit breaker model. All four models are used in the same simulation sequence. The developed model can be used for various simulations as a one-phase model or as a three-phase model. In the paper, the model performance is verified and its practical applications are shown.

Faster than real time: Dynamic security assessment for foresighted control actions

In this paper, implementation of power system dynamic security assessment (DSA) into real time simulation environment is described. For this purpose, a powerful simulation system has been used and a flexible security assessment framework developed. The DSA system constructed is user oriented and enables simple evaluation of power system security. The assessment is made in respect to some user defined security constraints considering normal or contingency provoked system operation. For reporting of the results different visualization formats are available. The DSA system is fully automatic and can process any number of study cases without user interaction. It targets high flexibility in power system research and maximum performance at minimum hardware requirements.

Monitoring and Reporting of Security of Power System Low-frequency Oscillations

Abstract This article deals with the monitoring and visualization of security of power system oscillation modes. The monitoring is performed by means of a performance index based on the traditional stability measure, but it reports on relative changes in the system low-frequency characteristics in a more indicative manner. In addition to introducing a dramatic progression at marginal changes in the modes characteristics, the index also communicates the “relative distance” to the dangerous system stages by reporting the available security margin. Using the index, system states can be meaningfully visualized. In this article, the matrix visualization technique is applied for that purpose. The technique sufficiently facilitates human interaction for identification of the system states under different network and operating conditions.

Vision 2020 dynamic security assessment in real time environment

In this paper, implementation of power system dynamic security assessment (DSA) into real time simulation environment is described. For this purpose, a powerful simulation system has been used and a flexible security assessment framework developed. The DSA system constructed is user oriented and enables simple evaluation of power system security. The assessment is made in respect to some user defined security constraints considering normal or contingency provoked system operation. For reporting of the results different visualization formats are available. The DSA system is fully automatic and can process any number of study cases without user interaction. It targets high flexibility in power system research and maximum performance at minimum hardware requirements.

White LED compared with other light sources: age-dependent photobiological effects and parameters for evaluation

Ergonomic science at work and living places should appraise human factors concerning the photobiological effects of lighting. Thorough knowledge on this subject has been gained in the past; however, few attempts have been made to propose suitable evaluation parameters. The blue light hazard and its influence on melatonin secretion in age-dependent observers is considered in this paper and parameters for its evaluation are proposed. New parameters were applied to analyse the effects of white light-emitting diode (LED) light sources and to compare them with the currently applied light sources. The photobiological effects of light sources with the same illuminance but different spectral power distribution were determined for healthy 4–76-year-old observers. The suitability of new parameters is discussed. Correlated colour temperature, the only parameter currently used to assess photobiological effects, is evaluated and compared to new parameters.

Power system dynamic security inference — Conceptual solution

In this paper a conceptual solution is presented for power system dynamic security inference and visualization. It enables collecting information on power system security aspects and delivers an over-all system performance by means of a single indicator. Visualizing the indicator in a clear and meaningful manner can help identifying system states and focuses ones attention to the dangerous ones.

Dynamic security assessment using time-domain simulator

In this paper, implementation of power system dynamic security assessment (DSA) into a time domain simulation environment is described. The paper discusses general characteristics of DSA in time domain and presents a framework for software implementation. The implemented DSA system is user oriented and enables simple investigation of power system security in normal or contingency provoked system conditions. Using continuous processing, DSA is fully automated and can process any number of cases without user interaction, however, with some user established security constraints. If a security violation is detected, the contingency is documented and more detailed case study is possible. The paper presents methodology of implementation of DSA into well established simulator PSS™NETOMAC, an overview of the considered power system security constraints and visualization options developed. The paper concludes with a case study. The DSA system was tested for performance on a generic single processor computer.

Assessment of power system dynamic security by relying on conventional simulation domain

A contingency evaluation procedure is presented able to efficiently classify system states by completely relying on conventional time domain simulation. The classification is made on the basis of dynamic security criteria including threshold levels of important system parameters and limits of system stability. Dedicated time-domain methods are used for the screening process. All are well established and available in the associated literature. The methods are implemented into the PSS®NETOMAC simulator and controlled through a wrapper interface so as to allow high-level of automatism and flexibility of computations.

Performance evaluation of indices for transient stability

In this paper the established performance indices for screening and ranking of power system contingencies are applied. The indices capture the change in the system state variables and deliver the degree to which it is provoked under different operating states. The indices refer to the generator coherency, transient energy conversion, dot products derived from the classical concept of the transient energy function, and generator angular deviation. The indices are calculated using the time domain simulation and a power system model.