Analysis PQP foundries. Deflection compensation voltage using off-load tap changer and on-load tap changer

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Analysis PQP foundries. Deflection compensation voltage using off-load tap changer and on-load tap changer

Kalimullin A.T.

Аннотация

В статье рассмотрены такие актуальные вопросы, как расчет и анализ показателей качества электрической энергии в литейном цехе. Показатели качества электроэнергии, выходя за допустимые пределы, в совокупности с другими факторами приводят к экономическим потерям. На качество электрической энергии может влиять большое количество факторов, один из которых - потребитель с переменной нагрузкой (дуговые сталеплавильные печи, сварочные аппараты и т.д.). В данной статье показано как индукционные плавильные печи влияют на напряжение, в результате чего требуется компенсация. Регулирование отклонения напряжения производится с помощью установок ПБВ и РПН цеховых трансформаторов.

Ключевые слова: показатели качества электроэнергии, индукционные печи, отклонение напряжения, качество электроэнергии.

Kalimullin A.T.¹, Leskov I.A.², Trotcenko V.M.³, Temnikov E.A.⁴

¹Postgraduate studentt of the department of power supply for industrial enterprises, ²Student 5th year, the Energy Department, ³Student 5th year, the Energy Department, ⁴Student 5th year, the Energy Department, Omsk State Technical University

Analysis pqp foundries. Deflection compensation voltage using off-load tap changer and on-load tap changer

Abstract

The article deals with topical issues such as the calculation and analysis of indicators of quality of electric energy in the foundry. Power quality, going beyond the limits, in combination with other factors result in economic losses. The quality of electric power may affect a large number of factors, one of which - the consumer with a variable load (electric arc furnaces, welding machines, etc.). This article shows how the induction-melting furnace affect the voltage, thereby requiring compensation. Regulation of voltage deviation is performed by off-load tap changer transformer load tap changer shop.

Keywords: power quality indicators, induction furnaces, voltage deviation, measuring power quality, power quality.

Electrical energy is one of the main components of the production process. In connection with the development of market relations in the power of electricity to be regarded not only as a physical phenomenon, but as a commodity, which must comply with certain quality and market requirements. Power quality has a significant impact on the reliability of the electrical equipment and the technical and economic indicators. Power quality, going beyond the limits, in combination with other factors result in economic losses.

High quality electricity and its uninterrupted supply, so-called, reliability, these are the main components of the power supply. The quality of electrical power may affect a large number of factors, which break it and lead to deterioration. Grid itself can be a source of various kinds of violations, their variety is very great. This may be a thunderstorm strikes, switching and switching equipment.

All the main indicators of quality of electric energy and their tolerances and variations collected in GOST 32144-2013 «Of electrical energy. Compatibility of technical equipment. Power quality limits in public electrical systems» [1]. Consumers with variable load makes a tangible contribution to the reduction of power quality. For the role of the variable load may extend drives reversible rolling mills, electric arc furnaces, welding machines, etc. In this article, we are interested in induction melting furnaces and assess their impact on the deviation of voltage and consequently, the SCE.

Voltage tolerance is directly related to the natural diurnal, seasonal fluctuations and technological electrical load of household and industrial customers connected to the network. Among other factors affecting the appearance of voltage fluctuation, it is necessary to allocate the regulation voltage generators of power, the use of RPN, including reactors and synchronous condensers in substations power systems. Also, changes in the power system voltage nodes cause the switching circuits in the electrical networks, which are the consequence of the change of its parameters.

Each power receiver is designed to operate at rated voltage and should ensure the normal operation when the voltage deviation from the nominal value by a predetermined GOST. When changing the voltage within this operating range can vary the values of the output power setting of the receiver, for example, the temperature in the electro-thermal installation, the illumination from the lighting installation, the useful power to the motor shaft, etc.

Along with the change in the output parameters, and in some cases even when the output parameters do not change, the change in voltage leads to a change in power consumption of the receiver power.

Work electrothermal installations with a significant decrease in the voltage deteriorates significantly, as it increases the duration of the process. Induction melting furnace of industrial frequency and high frequency are the three-phase electrical load «quiet» mode. increased frequency furnaces are powered by frequency converters gate to which is applied an alternating current voltage of 0.4 kV. Induction furnaces have low power factor of 0.1 to 0.5.

The basis of the analysis taken by the foundry plant JSC «Credo». The analysis of the SCE plant and determine whether the voltage adjustment is required.

Driving foundry plant is show in Figure 1.

Fig. 1 - The scheme for calculating voltage variations on tires 0.4 kV transformer substation

electric energy voltage deviation

Payment voltage deviation is performed by installation guild transformers WSP devices that have changed the transformation ratio. All transformers in the shop have a 5-speed switching by 2.5 % each, which allows you to adjust the voltage within ± 5 %. Transformers ТРДН-25000/110 115/11 kV voltage have ±16% on-load tap changer device (9 steps by 1.78 %) [2].

For the calculation of a given level or voltage deviation at point 1 (point section of industrial enterprises and power grid networks):

_· in the period of maximum plant load = 0

_· during low load plant = 2,5

Define the voltage deviation during peak load and minimum load on tires 0.4 kV transformer substations of the following expressions plant [2]

where , - voltage drop in the transformer GРP between maximum and minimum loads, %;

, - voltage drop in the transformer i-th TP between maximum and minimum loads, %;

, - аdditives voltage generated by the transformer load tap changer switch GРP between maximum and minimum loads, %;

- additive voltage generated by the i-th transformer TP, %:

, - voltage loss in the cable line from the GPP to the i-th TP between maximum and minimum loads.

When calculating the voltage drops in transformers and cables, for a minimum load is taken equal to the load 0,25Р_р or 0,25I_pi.

Define the voltage loss on all parts of the circuit from the transformer to the GРP tires 0.4 kV package transformer substation.

1) Voltage losses in transformers GРP

The load of the GРP

On 1 transformer GРP

Resistance transformer ТРДН-25000/110

2) Voltage drop in the cable lines

Calculation results are listed in Table 1.

3) Resistance of shop transformers

ТМЗ-400/10

Calculation results are listed in Table 2.

Table 1- voltage loss in the cable lines

Table 2 - Loss of voltage transformers in shop

Table 3 - Calculation of the voltage deviation between the maximum and minimum loads

According to the Standard, at the receiver end is permitted voltage deviation within ± 5% of U_nom for 95 % of the time of day and ± 10 % of U_nom within 5 % of the time of day [1].

The analysis of the results, we can conclude that at 0.4 kV buses voltage deviations during peak load, correspond to GOST 32144-2013, so the regulation is not required. A voltage deviation during low load does not match the guests, so you need to change the control level transformers.

Compensation voltage deviation is made by adjusting the setting of the off-load tap changer transformers at the appropriate level +0% and on-load tap changer transformers ISS on stage: .

The resulting voltage deviation compensation value, GOST 32144-2013, with no need for daily voltage regulation [3]. The results after adjustment values shown in Table 4.

Table 4 - The values of voltage deviation between the maximum and minimum loads for the selected control steps

Performing simple calculations, you can estimate the quality of the power of a single shop of the plant and adjust beyond GOST PQP consequently, reduce the losses of the enterprise as a whole.

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