ANALYSIS OF REACTIVE POWER COMPENSATION IN INDUSTRIAL ENTERPRISES, ITS IMPORTANCE AND PRODUCTION METHODS

 

ABSTRACT

The article examines information about the consumption of reactive power at industrial enterprises, the processes of its generation and compensation of reactive power. One of the main issues at the design stages of industrial power supply systems and during their operation is the issue of reactive power replenishment (compensation). This problem is related to the task of generating a sufficient amount of energy for the consumer of reactive power, also known as compensation, and includes the selection of appropriate sources, their calculation and power regulation, the placement of sources in the power supply system.

АННОТАЦИЯ

В статье исследуются сведения о потреблении реактивной мощности на промышленных предприятиях, процессах ее генерации и компенсации реактивной мощности. Одним из основных вопросов на этапах проектирования промышленных систем электроснабжения и при их эксплуатации является вопрос восполнения (компенсации) реактивной мощности. Эта проблема связана с задачей выработки достаточного количества энергии для потребителя реактивной мощности, также известной как компенсация, и включает в себя выбор подходящих источников, их расчет и регулирование мощности, размещение источников в системе электроснабжения.

 

Keywords: reactive power, electrical networks, dissipated power, reliability, quality indicators, electricity.

Ключевые слова: реактивная мощность, электрические сети, рассеиваемая мощность, надежность, качественные показатели, электроэнергия.

 

The appearance of the name "reactive" power is related with the need to allot power consumed by the load, a component that originates electromagnetic fields and provides the motor torque. This element happens when the load is inductive. For instance, when connecting electric motors. Nearly, whole household loads, not allude to industrial commodity, are inductive to single degree or other. Electrical apparatus consumes energy while operation. In this case, the whole power consists two components: active and reactive. Reactive power does no useful work, but make known extra losses into the circuit. Consequently, they strive to decrease it, for which they come to different technical solutions for compensating reactive power in electrical settings. [1, p. 85].

The whole electrical power consists of active and reactive energy:

                                                           (1)

here: Q – reactive power, P- active power.

In electrical networks, when the load has an active character, the flowing current is in phase from the voltage. Unless the load is inductive (motors, transformers at no load), the current lags beyond the voltage. When the load is capacitive (capacitors), the current conducts the voltage. [2, p. 43-48]

 

Picture 1. Phasor diagram represents the relationship of powers

 

Reactive power happens in magnetic and electric fields, which are characteristic of inductive and capacitive loads when working in AC circuits. When a resistive load is operating, the voltage and current phases are the same and coincide. When an inductive load is connected, the voltage lags behind the current, and when a capacitive load is connected, it leads. In a single-phase power system, reactive power comes from the interaction of generator windings and any inductive loads on the system, and it's bad because then you have this energy exchange between the load and source going through the whole transmission system, overloading lines and resulting in losses. [3, p. 33-37].

 

Picture 2. Several scenarios of current phase displacement relative to voltage and what that means for the position of the power waveform

 

In order to reduce the reagent, reactive power compensation equipment are used, they are constantly used as a power compensator:

a) Synchronous motors;

b) capacitor banks;

Since the amount of reactive power can change over time, it means that compensators can be:

1. Automatic - compensation steps change depending on the state of the network

2. Dynamic - compensate when the load quickly changes its character.

3. Unregulated - a capacitor banks without the possibility of disconnecting individual capacitors to change the capacity

The circuit uses, depending on the amount of reactive energy, from one to a whole bank of capacitors that can be input and output from the circuit. Then the control can be:

manual (circuit breakers);

• semi-automatic (push-button posts with contactors);
• uncontrolled, then they are connected directly to the load, turn on and off with it.

Capacitor batteries can be installed both at substations and directly near consumers, then the device is connected to their cables or power buses. In the latter case, they are usually calculated for individual compensation of the reagent of a specific motor or other device - it is often found on equipment in 0.4 kV electrical networks. [4, p. 33-37]

 

Picture 3. Circuit diagram of reactive power static compensator and the schemes of connection and control of reactive power series compensation devices SCB

 

Centralized compensation is did either at the border of the balance section of the networks, or at the substation, and it can be done in 35 kV high-voltage settings. The good thing is that it unloads high-voltage lines, but the bad thing is that the 0.4 kV lines and the transformer itself are not unloaded. This method is cheaper than the others. At the same time, it is possible to centrally unload the low side of 0.4 kV, then the UKRM is connected to the buses to which the secondary winding of the transformer is connected, and accordingly it is also unloaded. [5, p. 11]

There may also be a group compensation option. It is an intermediate type between centralized and individual. Another way is compensation with synchronous motors, which can compensate for reactive power. It appears when the engine is in overexcitation mode. Такое решение используется в сетях 6 кV и 10 кV, также встречается и до 1000В. The advantage of this method over the installation of capacitor banks is the possibility of using a compensator to perform useful work (rotation of powerful compressors and pumps, for example). [5, p. 1019-1023]

 

Picture 4. Inside a power compensation enclosure

 

Power factor correction is one of the best investments to reduce energy costs with a short payback. In a large number of cases, the design and dimensioning work has been made more difficult by the fact that, in a company´s internal low-voltage installation, and also in the medium-voltage supplying it, the proportion of network harmonics has grown increasingly over the last few years. Power converters, electronically controlled drives, static frequency converters, televisions and computers feed harmonic currents into the supply network. These harmonics might be amplified by the network impedances and capacitors installed. The freedom from harmonics also minimizes interference with other devices being powered from the same source. [6, p. 18-24]

 

Picture 5. The characteristics of the change in driving current of the motors

 

The graph shows the U-shaped characteristic of a synchronous motor, which reflects the dependence of the stator current on the field current. Below it, you see what the cosine phi is. When it is greater than zero, the motor has a capacitive character, and when the cosine is less than zero, the load is capacitive and compensates for the reactive power of the rest of the inductive consumers.

Conclusion

The importance of reactive power compensation is beyond doubt. The stability of the energy system and the voltage value at consumers are associated with the reactive power mode and the solution to the problem of its compensation. The use of the power of generators and transformers, the cross-sections of cables and wires depends on the solution of the compensation problem. The amount of electricity losses in the elements of electrical networks also depends on the mode of reactive loads and their compensation.

The main reactive load in power systems is created by industrial enterprises. Hence, it is clear how important it is to carry out measures to compensate for reactive power at industrial enterprises. As mentioned above, first of all, under all conditions, enterprises should take measures to reduce the reactive power of the electricity receivers themselves. However, these measures alone are insufficient.

 

References:

1. Konstantinov B.A., Zaysev G.Z. Kompensasiya reaktivnaya moshnosti. L Energiya, 1996. Ukaz po kompensasii reaktivnoy moshnosti v raspredelitelnix setyax. M. Energiya, 1994 g. p. 85
2. Khosiljonovich K. I., Ergashevich S. S., Khakimovich E. A. Development of the algorithm of calculation of reactive power by harmonic components //Global Journal of Engineering and Technology Advances. – 2019. – Т. 1. – №. 1. – p. 043-048.
3.  Xoliddinov I.K. i soavt. Modelirovaniye rascheta koeffisiyenta nesimmetrii napryajeniy s pomoshyu Simulink (Matlab) // Amerikanskiy jurnal prikladnix nauk. - 2020. - T. 2. - №. 10. - p. 33-37.
4. Xoliddinov I. X., Tuychiyev Z. Z. Analiz rascheta slojnix elektricheskix sxem v programme multisim //Glavniy redaktor: Axmetov Sayranbek Maxsutovich, d-r texn. nauk; Zamestitel glavnogo redaktora: Axmednabiyev Rasul Magomedovich, kand. texn. nauk; Chleni redaksionnoy kollegii. – 2021. – p. 11.
5. Hikmatilla Sherzodjon O’G’Li Ne’Matonov Мatlab dasturida elektr energiya tizimidagi katta turtkilar natijasidagi dinamik turg’unliginig matmatik va fizik modellarining tahlili // Scientific progress. 2021. №6. p. 1019-1023.
6. Ponomarenko O. I., Xoliddinov I. X. Avtomatizirovannaya sistema analiza i upravleniya kachestvom elektroenergii //Glavniy energetik. – 2021. – №. 1. – p. 18-24.
7. Ismoilov I. K., Xalilova F. A. Regulirovaniy aktivnoy i reaktivnoy moshnosti sinxronnogo generatora pri podklyuchenii k seti //Universum: texnicheskiye nauki. – 2021. – №. 1-3 (82).