In recent years, with the increasing renewal of power equipment and the gradual implementation of rural network and urban network transformation, the structure of the distribution network is becoming more and more reasonable. The power supply capacity of lines and distribution transformers is increasingly enhanced, and the reliability and safety factor of power supply are all obvious However, according to the data, the power factor of industry and agriculture generally fails to meet the requirements stipulated by the relevant departments, and the reactive power has not been fully taken seriously by everyone.
Article 1 of Chapter 1 of the Regulations on Power System Voltage and Reactive Power Management clearly stipulates: "...... Reactive power is an important factor affecting the quality of the voltage. All levels of the power sector and each power unit We must strengthen the voltage and reactive management, and effectively improve the power grid and the user's power supply voltage. "
Written theory and years of practical experience have shown that reactive power compensation for the improvement of voltage quality and economic benefits have great benefits; however, it has not been well promoted, the following aspects of reactive power compensation to do The following simple analysis.
First, the meaning of the implementation of reactive power compensation
1, the impact of voltage
There are always problems such as low voltage at the end of the power distribution network. The reason for this is mainly due to the lack of reactive power except the problems of the power grid itself. When the grid is transmitting power, the current will have a voltage loss Δ U on the impedance of the line. If the starting voltage is U1 and the terminal voltage is U2, the voltage loss can be calculated by the following formula: U = U1-U2 = (PR + QX ) / UN
In the type P-line transmission of active power kW
Q - Reactive power delivered by the line kvar
UN- line rated voltage kV
R, X-line resistance, reactance Ω
We keep the active power constant, and R and X are the fixed values. The smaller the reactive power Q, the smaller the voltage loss is, the higher the voltage quality will be. When the line is installed with parallel capacitor compensation device with reactive compensation capacity QC, The voltage loss becomes:
U` = [PR + (Q-QC) X] / UN
It can be seen that, after reactive power compensation, the reactive power Q becomes smaller, which limits the transmission of reactive power in the power grid, correspondingly reduces the line voltage loss and improves the voltage quality of the distribution network.
2. The impact of line loss
Reactive power not only affects the voltage quality of the power distribution system, but also leads to the increase of power supply line loss in the distribution system. The power loss of the lines and transformers in the distribution network is:
△ P = 3I2Rε * 103 = P2Rε * 103 / UN2COS2φ
P-line transmission of active power kW
COSφ is the power factor;
Rε is the equivalent resistance of each phase conductor;
UN is the operating voltage;
It can be seen from the formula that when the line active power P and the line resistance Rε are not changed, the power loss of the line is inversely proportional to the square of the power factor. The larger the COSφ, the smaller the △ P, that is, the smaller the line loss of the power network.
In summary, reactive power compensation measures will greatly improve the quality of the line voltage loss and voltage gain, if the way to adjust the voltage transformer to increase the voltage, the effect is less than half of reactive power compensation, and investment is at least reactive More than 10 times, the following we have a brief analysis of the capacitor in reactive power compensation in the specific implementation.
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