In recent years, the reactive power control has plays an important role in maintaining a secure voltage profile in a large scale transmission system. Though it is needed for the acceptable functioning of various electrical systems such as transmission lines, motors, transformer, etc. It is essential for the operation of all most all of the electromagnetic energy devices for producing the magnetic field. In some cases it is forcefully injected into the power system network to maintain higher node voltage. Reactive Power is one of the total power components in an AC circuit that has its origin in the phase shift between a sinusoidal voltage and current waveforms. It is a consequence or byproduct of an AC system that travel back and forth in the power conductor, i.e., flowing to reactive components from a source during one half cycle and back to the source during another half cycle of an AC waveform.
The average value of power is therefore zero, which implies that the load never get consumes reactive power. In case of a three phase circuit, at any instant reactive powers of three phases add up to zero. To differentiate from active power which performs useful work, reactive power is measured in “VAR” rather than in Watts. Using capacitors to supply reactive power reduces the amount of current in the line. Since line losses are a function of the current squared, I2R, reducing reactive power flow on lines significantly reduces losses.
Over a long distance power transmission, additional reactive power losses occur due to the large reactive impedance of high voltage transmission system. To avoid excessive reactive power transmission, generation and consumption of reactive power should be as close as possible to each other; otherwise, it will result in inappropriate voltage profile. Transmission lines, transformers, induction motors, furnaces, reactors, chokes, wound control gear, consume reactive power, and its transmission is highly localised. Therefore, reactive power is provided to them by some localised sources. For LT Loads, it can be controlled by ‘Intelligent Power Factor Control Relay’. By excitation system of the Synchronous generator, supply and demand of reactive power can be adjusted for desired voltage level.
In an alternating current power system, Power comprises of two components, active power and reactive power. Useful work is accomplished by active power while reactive power improves voltage stability and avoids voltage collapse. By regulation of reactive power the parameters of a power system like Utilisation of active power, Voltage stability, Power factor, System efficiency, Energy cost and Power quality can be controlled.