A Mathematical Modeling of Double Exponential Voltage – Waveshape (Impulse Generator) For Power Substations Using Laplace-Transform (original) (raw)

This paper presented a framework of mathematical model of double exponential voltage waveshape for purpose of generation of impulse voltages and currents. An impulse voltage is a unidirectional voltage which, without appreciable oscillations, rises rapidly to a maximum value and falls more or less rapidly to zero. The maximum value is called the peak value of the impulse and the impulse voltage is specified by this value. Small oscillations are tolerated provided that their amplitude is less than 5% of the peak value of the impulse voltage. An impulse voltage develops without causing flash over or puncture, is called a full impulse voltage, but if flash over or puncture occur thus causing sudden collapse of the impulse voltage is called a chopped impulse voltage. A full impulse voltage is characterized by its peak value and its two time interval, the wave – front the wave-tail time intervals. The wave front time of an impulse wave is the time taken by the wave to reach to its maximum value starting from zero value. It is difficult to identify the start and peak points of the wave, hence the wave front time is specified as 1.25 times (t 2 – t 1), where t 2 is the time for the wave to reach to its 90% of the peak value and t 1 is the time to reach 10% of the peak value. Since (t 2 – t 1), represents about 80% of the wavefront time, it is multiplied by 1.25 to give total wave front time. Evidently, some basic concept of circuit analysis including Laplace transform principle were used to solve for the double exponential voltage wave-shape, formulated from the circuit analysis. The solutions of the formulated problems represents the model for the exponential growing voltage/currents wave shape representatively. Some specific assumptions were made in analyzing this models. The results from the analysis shows an exponential increase in voltage values with respect to time which represents the growth of the voltage pattern. This result are were represented on graph using matrix-laboratory (Matlab). Most importantly, the protection of power substations against lighting over voltages is critical reliable operation of electrical network since a frequent initiation of lighting surges etc without adequate moderation of the developed overvoltage may serious damage equipment, facilities etc resulting in power supply interruptions. This means that this paper will analyse time the voltage profile with respect to time in is order to access at what point the voltage is critical not adequate for power system equipments.

A New Voltage-Mode Universal Biquadratic Filter Using Single UVC

The paper presents a new universal biquadratic filter using single universal voltage conveyor (UVC), two resistors and two capacitors. The offered structure has three inputs and one output and can realise all the five basic biquad-ratic filters: high-pass (HP), low-pass (LP), band-reject (BR), band-pass (BP) and all-pass (AP) from the same circuit topology. The proposed universal filter also provides following advantageous features, not available simultaneously in any UVC based universal biquadratic filter so far: (i) low active and passive sensitivities, (ii) independent control of natural frequency (ω 0) and bandwidth (BW) and (iii) no requirement of any component matching condition and inversion of input signal(s) (as needed in most of the earlier reported structures). The workability of proposed structure has been presented by SPICE (Version 16.5) simulation using 0.18 µm TSMC technology.

SIMULATION OF IMPULSE VOLTAGE TESTING OF POWER TRANSFORMERS USING PSPICE

Impulse generator is an indispensible high voltage set. It simulates the voltage due to lightning and switching surges and used for testing of insulation of various electrical equipments like transformer, insulators etc. The standard impulse waveform could be used to test the strength of electrical equipments against the lightning. Lightning characteristics and standard impulse wave form are related to each other. But the lack of realization about relation between them would make the solution to produce better protection against lightning surge becomes harder. Lightning impulse voltage and standard impulse voltage (1.2/50μs) are similar to each other. So, to achieving better protection of high voltage equipment study of impulse voltage waveform is very important. In this paper comparison has been made between standard impulse waveform obtained by simulating Marx impulse generation circuit in Pspice software and practical Marx circuit. This impulse waveform can be used to test the capacity of electrical equipment against the lightning and switching surge voltage.

AMPLIFICATEUR OPERATIONNEL : REALISATION DE FILTRES DU PREMIER ORDRE 1

L'amplificateur opérationnel est considéré comme idéal. La résistance R 3 sur les schémas (qui a pour but de limiter la tension d'offset de l'amplificateur réel) ne sera pas prise en compte : sa tension aux bornes est nulle. On supposera de plus que la courbe de réponse de l'amplificateur est idéale : gain en tension constant quelle que soit la fréquence.

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