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The estimation of influence of lotage oscillation on man in the presence of electrical receivers with sharply alternate load in network |
Introduction
Growth of unit power and amount of electrical receivers with sharply changing load in network (arc stoves, ore-thermal facilities, rolling mills, home appliances) made the task of estimation of permissibility of voltage fluctuations created by them very actual. This testifies the setting of norms of voltage fluctuations of tension in [1] and in standards of the International electrotechnical commission (IEC).
Voltage fluctuations cause fluctuations of virtual values of light flux of lamps, and, consequently, the illumination. It causes additional fatigue and, as a result, the decrease of labour productivity and worsening of health. Admission of voltage fluctuations is estimated on the dose of voltage flicker, which is standardized by the standards of IEC and GOST 13109-97.
In planning of the power supply systems there is a necessity in prognostication of doses of voltage flicker by known characteristics of the electric loading of sources of interference - electrical receivers with sharply changing load in network.
Dynamic models of electromagnetic compatibility
Estimation of EMC concludes in estimation of reaction of the Y(t) object on a hindrance X(t). Mathematical descriptions of interference and object, usually called models, are required in this connection. Dynamic models are used most often. Often swaying links are used in the filters of dynamic models, for example in the flickermeter filter of International electrotechnical commission - device by which admission of voltage fluctuations is estimated in electric networks.
Vibrations of tension occupy the special position among consumers properties of electric power, because they affect human health: the rapid changes of luminosity, tensions caused by vibrations on the clamps of lamps, additionally tire human, which conduces to worsening of sight and diminishing of labour productivity. Thus, the task of objective estimation of admission of fluctuations is very actual.
The model of flickermeter is described in the documents of the International electrotechnical commission (IEC) [3, 4] - device which estimates admission of voltage fluctuations in electric networks. This model is accepted also in the standard of Ukraine on quality of electric power [2]. In this paper term "flicker-model" is used further.
Flicker-model basis is made by a weighing filter (figure 1.1) which includes: 1 is high-frequency (HF) filter of the first order with cutoff frequency fc1=0,05 Hz, 2 is Batterworth filter of 6th order with cutoff frequency fc2=35 Hz, and 3 is a perception filter.
Figure 1.1 - The flow diagram of weighing filter of flicker-model
The summary transmission function of weighting filter of flicker-model is product of transmission functions of three filters: HF, Batterworth, and perception filter:
WFW(p)=W1(p)W2(p)W3(p)
Thus, processes in a weighing filter are described by differential equation of eleventh order. The calculation of descriptions of reaction of sight is brought to solving of this differential equation.
Dose of voltage flicker
The task of this paper is application of new methods for the calculation of reactions of filters of dynamic models of EMC on casual electromagnetic interferences: as applied to flickermeter - reactions of weighing filter, and further, for the calculation of dynamic indexes of EMC, namely doses of voltage flicker.
Normalization of the vibrations curves possesses some substantial flaws.
The concept of flicker dose is based on estimation of man discomfort from fluctuations of light intensity [7]. A flicker-model for estimation of voltage flicker dose [3, 4] consists of three blocks: weighting filter WF, quadratic inertia smoothing
QS and statistical processing SP (figure 1.2). An interference X(t) means a difference between the process U(t) and its one-minute trend. An interference is measured in percents from the level of nominal tension Un.
A weighting filter models an incandescent (60 W, 230V) lamp and human visual system. Figure 1.2 - The structural diagram of flicker-model
The short-time flicker dose is determined with a formula
The permissible value of short-time dose is equal to 1. Methods of calculation of reactions characteristics
The analysis of existent models of EMC confirms that the basic task of estimation of dynamic indexes of EMC is determination of descriptions of reaction of Y(t) in the linear filter output: the average value Yс(t) and correlation function (CF) KY(t1, t2) or only dispersions DY(t).
This task can be solved by use of general formulas of random processes theory [11, 12, 13 - 17, 18, 19]. The calculation of average value does not meet difficulties. However, when calculating CF of interference, there is the module of argument τ, therefore at determination of CF and dispersions
of reaction it is necessary to execute bulky double integration twice: at τ + u < ν and τ + u > ν. Just the calculation of CF and dispersions by a theorem about deductions is labour intensive enough.
The indicated flaws of methods of calculation of filter reactions are removed by use of the method of partial reactions, offered by the department of EPG DonNTU [9]. Definition of research problem
It follows from the analysis of literature, that EMC indexes calculation methods offered in operating GOST 13109-97, and in particular doses of voltage flicker, have the substantial flaws. As a result, the following problems of research are defined in this paper:
1. The method of calculation of descriptions of random processes in the output of linear filters of models of EMC offered in [9] is to be applied for the calculation of voltage flicker dose, created by the different groups of electro-receivers.
2. The analysis of the executed calculations from point of influence of estimation of determination of voltage flicker dose on quality of electric power. Literature:
1. Куренный Э.Г., Ковальчук В.М., Коломытцев А.Д. Оценка качества электроэнергии с использованием моделей объектов // Материалы конференции «Качество электроэнергии в сетях промышленных предприятий». – М.: МДНТП, 1977. – С. 23-29.
2. ГОСТ 13109-97. Электрическая энергия. Совместимость технических средств электромагнитная. Нормы качества электрической энергии в системах электроснабжения общего назначения. – Введ. в Украине 01.01.2000.
3. Flickermeter. Functional and design specification. – Geneva: IEC Report. – 1986. – Publication 868. – 31 p.
4. IEC 61000-4-15: Electromagnetic compatibility – Part 4: Testing and measurement techniques. Section 15: Flickermeter – Functional and design specifications, 1997.
5. Лэм Г. Аналоговые и цифровые фильтры: Расчет и реализация. – М.: Мир, 1982. – 592 с.
6. Гутников В.С. Фильтрация измерительных сигналов. – Л.: Энергоатомиздат, 1990. – 192 с.
7. Mirra C., Sani G. Il fenomeno del flicker. Analisi delle sue caracteristiche. Techniche di misura e metodi di limitazione. – L’Elettrotecnica. – 1987. – Р. 805 – 822.
10. Алексеев С.В., Трейвас В.Г. Статистические характеристики токов дуг дуговых сталеплавильных печей // Изв. вузов. Электромеханика. – 1971. – № 1. – С. 78-82.
11. Электромагнитная совместимость электроприемников промышленных предприятий // А.К. Шидловский, Б.П. Борисов, Г.Я. Вагин и др. – К.: Наукова думка, 1992. – 236 с.
12. Шидловский А.К., Куренный Э.Г. Введение в статистическую динамику систем электроснабжения. – К.: Наукова думка, 1984. – 273 с.
13. Свешников А.А. Прикладные методы теории случайных функций. – М.: Наука, 1968. – 464 с.
14. Вентцель Е.С. Теория вероятностей. – М.: Наука, 1969. – 576 с.
15. Тихонов В.И. Статистическая радиотехника. – М.: Советское радио, 1966. – 678 с.
16. Тихонов В.И. Выбросы случайных процессов. – М.: Наука, 1970. – 392 с.
17. Пугачев В.С. Теория вероятностей и математическая статистика. – М.: Наука, 1979. – 496 с.
18. Грибанов Ю.И., Мальков В.И. Спектральный анализ случайных процессов. – М.: Энергия, 1974. – 240 с.
19. Пугачев В.С. Теория случайных функций и ее применение к задачам теории автоматического управления. – М.: Наука, 1962. – 821 с.
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