Focused Practice

I. Answer the following questions:

1. What is needed for the so-called intelligent disk drives?

2. What do disk drives currently come equipped with?

3. Are modern drives all standardized?

4. Where may high-level control of intelligent features best reside?

5. What intelligent features would allow drive makers to distinguish their products?

6. Who must computer manufacturers be convinced of the benefits of the new features to?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: Disk Drives.

SECTION IV

Energetics and power engineering

Unit 33

Grammar: The Infinitive. The Elliptic Sentences

Word List:

1. power system dynamics	динамика энергосистем
2. quasi-stationary assumption	квазистационарное допущение
3. phaser	метод фазовых выборок
4. steady state behaviour	поведение (режим) в устойчивом состоянии
5. transient analysis	анализ переходных процессов
6. on-line synchronous measurement	синхронное измерение в режиме «on line» ( в оперативном режиме)
7.classical impulse response approach	классический подход к реакции системы на скачки напряжения (тока)
8. power balance equations	уравнения сохранения (баланса) энергии
9. RLC network	цепь, содержащая резисторы, индуктивности и емкости
10. carrier frequency	несущая частота
11. band-pass system	полосно-пропускающая система
12. per se	сам по себе, по существу

Tools for Dynamic Analysis of the General Large Power System Using Time - Varying Phasers

Phaser representation of sinusoidal modulated signals is a powerful tool for analysing the steady state behaviour of voltages and currents in a linear RLC network. Phasers have been used for decades in the transient analysis of the power system under the quasi-stationary assumption, that is, the transients are assumed to be sufficiently slow so that they can be approximated to be stationary. This has been an excellent approximation for analysing most of the slow dynamic phenomena (much slower than the 60 Hz carrier frequency) studied in the past, but the error introduced by this approximation must be kept in mind while analysing some of the faster transients: ignoring this fact has led to some recent results of questionable validity in the literature.

In the power industry, using advanced communication facilities, on-line synchronous measurement of real time phasers is now becoming feasible. With the evolving digital signal processing technology, it is quite realistic to assume that time-varying phasers can be measured accurately in real time using cost-effective modules. Real time control designs based on the time variations of these phasers are also being explored in the power system industry. However the analysis using these phasers is still based on the classical quasi-stationary assumption that the variations of the phasers are very small. It becomes important to understand the theory base for the time varying phasers and the implications of their time variations on the error introduced in the quasi-stationary phaser analysis. In this paper, the time varying phaser concept will be developed from the basics.

In Communication theory, a notion of time varying phasers has existed for a long time in the context of modulation; for analysing narrow-band signals whose signal bandwidths (in the frequency domain) are much smaller than the carrier frequency. There, mostly the phasers are used for the frequency domain analysis of band-pass systems using the classical impulse response approach. Such a formulation, per se, is not applicable to the power system because the power system dynamics is nonlinear in the form of power balance equations and an impulse response analysis of the system may not be suitable for our purpose. Moreover, the narrow band assumption on the phasers is essentially equivalent to the traditional quasi-stationary assumption that their speeds are small so does not contribute much new information.