The abstract on a theme of master's work
Introduction
The growth of unit capacity of consumers with sharp variable load supply systems of industrial enterprises leads to an increase in the deviations and voltage fluctuations. Distortion power quality leads to significant damage. To ensure the quality of electricity requires additional costs. In this connection, problems arise reliable assessment of quality of electricity.
Currency of the theme. Existing methods do not account for unsteady modes of CPD, thus becomes urgent task to improve methodology for assessing the deviation and voltage fluctuations in these conditions.
The purpose of the work:
1. Improving methods for calculating the dose flicker.
2. Estimation of doses of flicker voltage networks with EAF.
3. Evaluating the effectiveness of measures to ensure power quality.
The idea of work. Initial data for the performance curves are digitized current and voltage obtained by the registrar RECON.
According to [1], voltage deviation is characterized by a steady rate of voltage deviation. Voltage fluctuations are characterized by: dependency scope of permissible voltage change their frequency of occurrence and a dose of flicker.
To measure the dose of flicker using a device called flikermetrom. According to [2] it consists of five units that perform the following tasks:
- modeling chain reaction "lamp-eye-brain";
- statistical analysis of flicker in real time and displays the results of measurements.
As used in this device model "lamp-eye-brain" does not take into account the slow adaptation of view, which leads to significant errors in accounting for low frequency flicker. Therefore, we propose to improve the methods for calculating the dose flicker. Also expected to study the effect of transient load changes on the DSP voltage fluctuation and flicker for a dose of heat.
The main tasks of research and development:
– to evaluate the EMC of the deviations and voltage fluctuations on the experimental plot the curve of voltage and current while working EAF;
– improving methods for calculating the dose flicker;
– development of EMC calculating the curves of voltage and current EAF.
Methodology and methods of research:
– methodology of experimental studies using RECON registrar;
– methods of probability theory and statistical dynamics.
The scientific novelty of this workis the slow adaptation of the calculation and measurement of doses of flicker.
Practical application:
– improving the model adopted by the flicker;
– creation of custom software for estimating parameters in EMC design practice.
Review of research and developments on the subject. The following scientists greatly contributed to the solution of problems connected with electrical energe quality: I. V. Zhezhelenko, A. K. Shidlovsky, I. Kartashov, P. Bodger, D. Bradley, S. Mirra, S. Gilbek, I. Sora. E. G. Kurennoy, E. N. Dmitrieva and A. D. Kolomyttsev study these problem. in DonNTU.
1 Normalization of QEE in the deviations and voltage fluctuations
According to [1] voltage deviation index is characterized by a steady voltage deviation, for which established the following rules:
– Normally allowed and the maximum allowable value of the steady voltage deviation δUy on the findings of the receivers of electric energy equal to ± 5 and ± 10% of nominal power;
– Normally allowed and the maximum allowable value of the steady voltage deviations at the points of common connection of consumers of electric energy to power grid voltage of 0,38 kV or more must be installed in contracts for the use of electrical energy between the energy supplying organizations and consumers with the need to fulfill the rules of this standard to the findings receivers of electric energy.
Voltage fluctuations are characterized by the following indicators:
–Scale voltage change;
– Dose of flicker.
2 Electric arc steel-melting furnaces
Particleboard, representing a powerful rezkoperemennuyu load, have a great influence on the change in voltage, first and foremost, on its own tires BPU power supply system. Changes on the buses power DSP, primarily manifested in the form of voltage deviations, the most important indicator of the quality of electricity and, in general, EMC.
Figure 1 - DC Arc Furnace
As the largest consumers of electrical energy particle board have a significant impact on quality of electrical energy to create a power supply almost all kinds of conducted electromagnetic disturbances, causing voltage distortion in the form of asymmetry, non-sinusoidal, variations and voltage fluctuations. [4] It is now established that the widely common type of distortion in power networks are higher harmonic. A few years later the levels of harmonics exceed the norm, unless steps are taken to reduce them.
Further development of steel production, associated with the transition from open-hearth steel production in electric arc furnaces, the increase in DSP power raises the question of the need for further development of methods for calculating and reducing the higher harmonics in industrial networks. [2]
3 Estimationof EMC in the deviations and voltage fluctuations
3.1 Assessment of voltage deviations in electric networks
Voltage deviation can occur as the fault of the power system, and on the consumer's fault, associated with reactive power imbalance.
In the [1] described method of determining the voltage deviations. The quality of electrical energy by a steady voltage deviation at the point of common connection to the mains deemed to meet this standard, if all measured for each minute over a set period of time (24 h) values of the steady voltage deviation in the range bounded by the maximum permissible values, not At least 95% measured over the same period, the values of the steady voltage deviation in the range, normally confined valid values [1].
3.2 Simulation of voltage fluctuations in the electromagnetic compatibility problems
In some problems of electromagnetic compatibility (EMC) to ensure the reliability needed to consider the process u (t) changes over time the instantaneous voltage (voltage curve): For example, when evaluating non-sinusoidal vibrations on tension. The standard [1] recommended that only an approximate solution: the voltage curve is taken as piecewise linear function. In addition, while there is uncertainty in choosing the type of approximation: in Fig. 3, and from the standard coordinates are connected by the slope and on the same figure. 2, b - vertical jump. This leads to errors in simulating the instantaneous values and, consequently, the estimates of indicators EMC.
a
b
Figure 2 - Voltage fluctuations of arbitrary shape (a) and having the form of a meander (b)
Figure 3
Periodic oscillations. Application of the method of half-waves, we first consider the example of a meander (Fig. 2 a) and harmonic oscillation (Fig. 2, b) with the scope δU and frequency of λ = 25 Hz, when the period is an integer tλ=1/λ=0,04 with s = 2 cycles, t50 = 0, 02 with 50 Hz sine wave. With a single trend tension on the tires periodically varies from 1+δU/2 to 1-δU/2.
In the case of a meander in the cycle of tl will be two half-wave with an amplitude and two - В2=√2(1-δU/2). Integration with ω100 = 200π gives a continuous function
where the factors of 100 and 200 have a dimension of 1 / sec. Her schedule is shown in Fig. 1, a thickened line. Amplitude of the oscillations remained unchanged, but the oscillations differ significantly from the idealized rectangular (dotted line): the total length of horizontal segments decreased by 2θ (from 0.04 to 0.02 sec), and no jumping. This leads to a decrease in dose flicker voltage.
Figure 4 - Simulation of rectangular and harmonic oscillations with frequencies: a, b - 25 Hz, d - 100 / 3 Hz
This example shows that it is impossible to reproduce the square fluctuations - only at low frequencies below 5 Hz, the error will not be large.
We now turn to the case when the cycle fluctuations is not a multiple of 0.02, which does not perform accurately simulated for a series of tλ. Overcome this fundamental difficulty can be accomplished in two ways: round the cycle in the lower and higher sides to multiple values of 0.02 and tλ1 tλ2, or increase the cycle time Tλ to a value greater than tλ [7].
3.3 Dose flicker. Flikermetr
In accordance with State Standard flicker is a subjective perception of human vibration of the light flux of artificial light sources, due to voltage fluctuations in the mains supply these sources. Flicker called the measure a dose of human susceptibility to the effects of flicker for a fixed period of time.
Testing electrical equipment can be carried out using flikermetra and calibration resistances. Testing is carried out by the power amplifier with a certain distortion performance ( < 3%) and specific output resistance. Work flikermetra is to use a set of filters to simulate the reaction of the human eye and brain to light flicker. Despite the difficulties, in terms of test, the procedure is reduced to relatively simple electrical measurements using calibrated equipment. Single-phase block diagram of the measurement is shown in figure 2.
Figure 5 - Testing of electrical equipment using flikermetra and resistances
Thus, the tendency to improve the quality of food lead to the recognition of companies supply problems flicker. Due to the need to measure the common types of equipment which are the causes of these problems are already developing measuring devices, one of them is flikermetr [8].
Conclusions
Particleboard characterized rezkoperemennym and random consumption of reactive and active power, which leads to deviations and voltage fluctuations.
Initial data for the job, or more precisely estimating the EMC of the deviations and fluctuations in voltage are digitized current and voltage curves obtained with the registrar RECON.
Currently used flikermetr not taken into account the slow adaptation of the view that leads to significant errors in accounting for the low-frequency component of the flicker, so we propose to improve the methods for calculating the dose flicker. Also expected to study the effect of transient load changes on the DSP voltage fluctuation and flicker for a dose of heat.
On the moment of writing this abstract the master's work was not completed. Its final variant can be obtained from the author or the scientific adviser after December 2011.
References
1. ГОСТ 13109-97. Межгосударственный стандарт. Электрическая энергия. Совместимость технических средств электромагнитная. Нормы качества электрической энергии в системах электроснабжения общего назначения. – Введ. в Украине с 01.01.2000.
2. ГОСТ Р 51317.4.15-99. Совместимость технических средств электромагнитная. Фликерметр. Технические требования и методы испытаний [Электронный ресурс]. – Режим доступа: http://www.gostrf.com/standart/Pages_gost/27528.htm
3. Салтыков В. М. Электромагнитная совместимость и энергосберегающие режимы электротехнического комплекса «система электроснабжения-дуговая сталеплавильная печь» / В. М. Салтыков //: диссертация ... доктора технических наук : 05.09.03 Тольятти, 2003 400 c. : 71 04-5/480
4. Салтыков В. М., Салтыкова О. А. Колебания напряжения в сетях параллельных дуговых сталеплавильных печей / В. М.Салтыков, О. А.Салтыкова // Электричество. 1981, №2, – с 53-56.
5. Д. Аррилага Гармоники в электрических системах / Д.Аррилага, Д. Брэдли, П. Боджер. – М.: Энергоатомиздат, 1990. – 215 с.
6. И.В. Жежеленко Показатели качества электроэнергии и их контроль на промышленных предприятиях//2-е изд., перераб. И доп.,– М.: Энергоатомиздат, 1986 – 186 с.
7. Дмитрієва О. М., Топчій В.О., Юшкова О.І. Імітація коливань напруги у задачах електромагнітної сумісності / О. М.Дмитрієва, В.О.Топчій, О.І. Юшкова //
8. Юшкова Е. И., Дмитриева Е. Н. Зарубежный опыт оценки дозы фликера в действующих сетях / Е. И.Юшкова, Е. Н.Дмитриева // Материалы Всеукраинской научно-технической конференции «Электротехника, электроника и микропроцессорнаятехника» 26–27 мая 2010 года. - Донецк, ДонНТУ - 2010, с. 154-155.