Static Var Compensator
A SVC (Static Var Compensator) is a high voltage system that controls dynamically the network voltage at its coupling point. Its main task is to keep the network voltage constantly at a set reference value.
The Static Var Compensator (SVC) is designed to decrease disturbances caused by changes in reactive power and voltage fluctuations in the normal operation of transmission lines and industry distribution systems. Disturbances may be caused by line switching, line faults, nonlinear components such as thyristor controls and rapidly varying active or reactive loads. Typical sources for these kinds of disturbances are electric arc furnaces and rolling mills.
These disturbances result in harmonics that load the supply network and cause voltage fluctuations. Varying loads can also create disturbances in the form of phase unbalance and voltage flicker phenomenon as well as create a need for additional reactive power.
The benefits of an SVC can be seen within a steel plant as a stable power factor in spite of varying loads at the plant, and externally when the disturbances do not affect the supplying grid. In short, the Static Var Compensator affects the following:
° Flicker reduction
° Voltage stabilization
°Reactive power compensation; improved power factor
° Increased voltage on the load bus
° Reduction of harmonics
Rapidly varying reactive power causes voltage fluctuations at the point of common coupling of a steel plant. The human eye perceives this frequency of voltage fluctuations as flickering lights.
Electrical Arc Furnace (EAF) operations can be intensely unbalanced especially in the beginning of the melting process. The three-phase induction motors suffer due to the unbalanced voltage supply. The unbalanced voltage causes reduced efficiency, overheating, noise, torque pulses and speed pulses to motor operations. The SVC operates in single-phase control mode, thus balancing the voltage.
Transmission of reactive power leads to significant voltage drops and current increases in the networks, which limits the transmission capacity of active power. Public utilities maximize their transmission line capacities by advising their customers to utilize local reactive power compensation.
The Static Var Compensator maintains the demand of reactive power within the limits set by utilities, thus avoiding penalties.
Non-linear loads, like Electrical Arc Furnaces, generate harmonic currents. The harmonic currents load the network and lead to voltage distortions. Distorted voltage may cause malfunctions in sensitive computerized devices or process control equipment.
The filter circuit of the SVC system is designed to absorb harmonics generated by loads as well as by Thyristor Controlled Reactors