ASSESSMENT OF THE LOSS OF ELECTRICAL ENERGY IN THE TRANSFORMER IN THE NOSINUSOIDAL MODE

АННОТАЦИЯ

В статье рассмотрена количественная оценка и определение процента дополнительных потерь электроэнергии, вызванных относительно синусоидального режима, с использованием значений высших гармонических составляющих напряжения, при несинусоидальных режимах работы трансформаторных пунктов в сети напряжением 10 кВ.

ABSTRACT

In this paper, the quantitative evaluation and determination of the percentage of the additional electricity loss caused by the sinusoidal mode using the values of the higher harmonic components of the voltage generated in the non-sinusoidal operating modes of the transformer points in the 10 kV network have been studied.

Ключевые слова: низновольтная сеть, показатели качества электроэнергии, несинусоидальность тока и напряжения, несимметрия тока и напряжения, потери мощности, дополнительные потери мощности.

Keywords: Low-voltage network, indicators of power quality, non-sinusoidal current and voltage, non-symmetry current and voltage, power loss, additional power loss.

Introduction

An important quantitative indicator assessing the technical condition of electrical networks and their mode of operation is the tendency to loss of electricity and its change. Despite significant progress in the development of electrical energy accounting systems, there is currently an increase in electricity losses, while the technical and commercial components of losses are also increasing.

According to international experts, the relative total losses of electricity during the transmission and distribution of electricity in low-voltage networks can be considered satisfactory if they do not exceed 4-5%. In Russia, their value does not exceed 11-13%, in Japan and Western Europe-6-7%. According to official data for low-voltage networks as of 2021 for the Kuva District of Fergana region of the Republic of Uzbekistan, these losses are on average 13.08% [1-2].

The high loss of electricity in low-voltage power networks is largely due to the following factors: technical parameters of the network elements, non-optimal operating modes, insufficient regulatory technical means, insufficient or unsatisfactory compensation of reactive power, nosymmetry of electrical loads, complete reliable failure of electrical energy accounting systems, an increase in the installed capacity of nosinusoidal loads. Sometimes in low-voltage power networks, the nosymmetry of electricity often exceeds the permissible values by a significant degree. This leads to the uncertainty of the initial data used in the accounting of electricity, calculation, analysis and prediction of losses by regulatory. [5-6-7]

In low-voltage power networks, the quality indicators of electricity are largely determined by the technical characteristics and operating modes of electrical receivers in consumers. Many problems with the quality indicators of electricity (the relationship between the enterprise and consumers) are currently not brought to the final solution, which is mainly due to the influence of consumers on the quality indicators of network electricity. One characteristic feature of electricity is that consumers are also forced to consume electricity whose quality performance is impaired by consumers, which does not negatively affect the quality of other electricity [2] Energy losses in low-voltage electrical networks are largely due to the qualitative characteristics of electricity. It is possible to single out the main indicators of the quality of electricity, which cause additional losses in the network:

• Rated voltage deviation;
• Voltage nosinusoidality coefficient;
• Voltage n-coefficient of harmonic constituents;
• Coefficients of voltage nosymmetries in reverse and zero sequence.

If there are high harmonic (YG) voltage organizers in the network, additional power losses will be available on electrical devices and power lines. At these losses, the effect of the coefficient of high harmonic (YG) constituents of the voltage will be noticeable.

Currently, the number of equipment that causes high harmonic voltages in industrial enterprises and utility consumers is increasing at a rapid opportunity. At enterprises, this is due to the extensive modernization of production, that is, with the introduction of modern electrical equipment: pulse rectifiers and frequency inverters, in the utility sector, personal computers, air conditioners, televisions, etc.are included.[7-8-9]

Methods

Currently, the number of equipment that causes high harmonic voltages in industrial enterprises and utility consumers is increasing at a rapid opportunity. At enterprises, this is due to the extensive modernization of production, that is, with the introduction of modern electrical equipment: impulse rectifiers and frequency inverters, in the utility sector, personal computers, air conditioners, televisions, etc are included.

Nonsinusoidal current and voltages also cause errors in electrical energy accounting devices. Especially the effect of the 11-13 - founders of YG has a significant effect on induction computing devices. But at present, induction electrical energy accounting devices in the network are low enough not to show their effect in general accounting.

If the coefficient of distortion of the Sinusoidal voltage is less than 5%, the effect of additional errors in measuring devices turns out to be insignificant.

In turn, the lack of electricity and the constant deterioration of its quality lead to additional power losses in electrical devices and electrical networks. The decrease in electrical energy quality indicators causes additional electrical energy losses to the following existing losses:

• To technical losses,
• To losses in Transformers,
• To wastes in asynchronous and synchronous motors,
• To losses in power lines
• To losses in compensatory devices

Additional active power losses due to voltage nosymmetry to losses in Transformers are expressed as the sum of their additional losses in the load-free (idling performance SI) and short-circuit (short-circuit QT) mode. Additional losses are also taken into account when a transformer is operating at a nosinusoidal voltage. These losses typically account for an average of 5% of the transformer's nominal short circuit losses, but additional losses increase dramatically if YG currents are flowing in the transformer and can reach 30-50%.[2]

Usually, for the transformer's idling mode of Operation, additional losses generated by Voltage nosinusoidity and nosymmetries are ignored, but in some works they are taken into account.

The additional loss generated by the voltage nosinusoidity in Idling performance mode is calculated by the following expression [1].

                                                        (1)

Here  - power loss in idling operation mode,

When working with a Nosinusoidal voltage, additional active power losses in the transformer are calculated by the following expression.

                                   (2)

Here  -short-circuit voltage, additional losses in the idling operation mode due to YG are neglected.

In Transformers in the nosymmetry mode, additional losses of active power can be determined using the following expression.

                                                             (3)

Here,  – coefficient  of reverse sequence voltage,  – everse  sequence voltage, in practical calculations, it is impossible to take into account additional losses in the idling operation mode due to voltage nosymmetry.

Results

To determine the coefficient of voltage n - harmonic constituting at Transformer points in a 10 kV power transmission network, the recording of quality indicators of elektra energy was carried out in accordance with the requirements of GOST 13109-97 on the Malika-01 device.

For Transformers TM160-10/0,4,located at the beginning of two networks, and TM160-10/0, 4, located at the end of the network, the values of electrical energy quality indicators were obtained. The studies were carried out in 0.4 kV tires according to [4], each measurement time was 24 hours.

In first picture  first transformer point is shown and in second picture coefficient of N - harmonic organizers of the voltage of transformers TM160-10/0,4 of the second transformer point are expressed in graphic form

Figure 1. 1 - values of the coefficient of N-harmonic organizers of voltage for the transformer

As can be seen from Figure 1, we can conclude that the odd harmonics of the harmonic constituting of the voltage prevail, especially 3, 5, 7, 9, 11, 13, 15 and in 17 harmonicas. These harmonic constituents also contribute the most to the total energy losses associated with its quality.

Figure 2. 2 - values of the coefficient of N-harmonic organizers of voltage for the transformer

As can be seen from Figure 2, the harmonic constituting of the voltage in tranformator No. 2 contain almost all harmonics up to 29. Often odd harmonics predominate, especially 3, 5, 7, 9, 11, 13 and 17 harmonics. These harmonic constituents contribute most to the total energy losses associated with its quality.

Discussion

The processing of the research results was carried out in an Excel package. Losses in the idling mode of operation from the YG voltage were not taken into account, since their value did not exceed 1% of short-circuit losses. To determine additional active power losses with a Nosinusoidal voltage (2) was calculated on the basis of the expression, the short-circuit power charge for Transformers was obtained from the passport data of the transformer and amounted to 1.28 kW. The short circuit voltage is 4.5%. The values calculated based on the data obtained are presented in tables 1.2.

Table 1.

Additional active power losses from high voltage harmonics for transformer number 1

Table 2.

Additional active power losses from high voltage harmonics for transformer number 2

For all Transformers, The average values of the coefficients of active power losses and voltage nosinusoidity by phases are presented in Table 3.

Table 3.

Average values of the coefficients of active power losses and voltage nosinusoidity by phases for Transformers

As can be seen from Table 3. with an increase in the coefficient of voltage nosinusoidity, the active power losses in the transformer also increase accordingly. It can be ignored if the additional losses caused by the voltage nosinusoidity coefficient in the idling operation mode do not exceed 1% of the short circuit losses. As a result of our research, additional losses generated by Voltage nosinusoidality amounted to 1 of short-circuit losses in transformer 3,5% , 2% in transformer 2,6.

Conclusion

In conclusion, it should be noted that at present the losses of electricity are included in the technical losses of energy, but it is also desirable to take into account additional power isrfos, which are formed from voltage nosinusoidality.

Nosinusoidal loads also affect the appearance of zero sequence currents in the transformer. Due to the zero sequence, a significant increase in resistance occurs, which increases power losses. In order to increase the energy efficiency and durability of transformer equipment, as well as to reduce electricity losses, it is necessary to take measures to reduce the impact of nosinosoidal voltages.

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