To understand what reactive power is, you need to have an idea of electrical power. Electrical power is a physical quantity that characterizes the rate of generation, transmission or consumption of electrical energy per unit of time.
The more power, the more work the electrical installation can do per unit of time. Power is measured in watts (product of Volts x Amperes).
Reactive power is the release of power, with an inductive nature of the load, which forms electromagnetic fields. For example, when connecting inductance, motor windings.
In electrical circuits, when the load has an active (resistive) character, the flowing current is in phase (does not lead or lag behind) from the voltage. Active energy is converted into useful energy – mechanical, thermal and other energy.
If the load is inductive (motors, transformers at no load), the current lags behind the voltage. Reactive power does not perform useful work, but it is necessary to create an electromagnetic field, which is necessary for the operation of electric motors and transformers.
When the load is capacitive (capacitors), the current leads the voltage.
Almost the entire load, in industrial production, to one degree or another has an inductive nature, which leads to an increased consumption of reactive power.
The consumption of reactive power leads to an increase in active losses and a voltage drop, which, accordingly, leads to an increase in the power of generators, transformers, an increase in the cross-section of the supply cables (due to a decrease in throughput).
When calculating networks for full power (active and reactive), often the cross-section of the cables, the ratings of the circuit breakers, etc. is chosen too high.
The cost of the consumed full power is formed from the calculation of active plus reactive power, an additional fee is charged for the flows (increased consumption) of reactive power, that is, the financial costs for paying for the flows of reactive energy, the purchase of cables of a larger cross-section, circuit breakers of a larger nominal value, become quite impressive.
In industrial production, to reduce the loads on cables, circuit breakers, generators, eliminate overloads and increase the power factor of electrical installations, reactive energy is compensated by capacitor units (hereinafter referred to as KRM).
KRM consists of a power cabinet in which there are: an input switch, protection fuses against failed capacitors, specialized starters, current transformers and a controller that monitors the consumption of reactive energy in real time and by connecting capacitors of different ratings reduces its consumption.