Power generation systems generate two power components, real power measured in watts, and reactive power measured in VARs. Both of these power components need to be produced and transmitted from the generator to the service customer. Real power flows from the generator to the load, and is used to drive loads such as electrical motors, create the heating effect in heaters, and the heating/lighting effect in lamps. Losses and associated voltage drops in the network are effected by the vector sum of real power and reactive power. Reactive power provided from a generation or capacitor source to the load is the component necessary for the operation of magnetizing currents in motors, transformers and solenoids which are part of a customer service load.
A capacitor bank is a grouping of several identical capacitors interconnected in parallel or in series with one another. These groups of capacitors are typically used to correct or counteract undesirable characteristics, such as power factor lag or phase shifts inherent in alternating current (AC) electrical power supplies. Shunt capacitor banks are used to an increasing extent at all voltage levels. There are a variety of reasons for this like the growing need for power transfer on existing lines while avoiding transfer of reactive power, better use of existing power systems, improving voltage stability, right-of-way and cost problems, voltage control and compensation of reactive loads. Three-phase capacitor bank sizes vary from a few tenths of MVAr to several hundreds of MVAr. Here we are using 25MVAR capacitor bank for this purpose.
Here, we have simulated an automatic scheme for switching of capacitor bank based on mvar requirement of the system. They automatically sense the voltage and reactive power using transducers. Output from these transducers are given to sensing circuit where it is compare with normal parameters (voltage and reactive power) of the system. If the condition satisfies it automatically switch on capacitor bank. And this normalises the system parameters.