Definition of active power: Active power is the power output by the generator that is used to drive the actual work of electrical equipment, and its unit is watt (W) or kilowatt (kW).
Functions and Significance
(1)Core Function: Directly convert into actual energies such as mechanical energy, thermal energy, and light energy to maintain the normal operation of electrical equipment.
(2)Grid Requirements: The active power must be balanced with the demand in real time. If the active power output of the generator is insufficient, it will cause the grid frequency to drop, and in severe cases, it may lead to equipment shutdown and grid collapse; if the output is excessive, the frequency will rise, which also poses a threat to equipment safety.
Definition of reactive power: Reactive power is the power used for the exchange of electric field and magnetic field energy in the circuit. It does not directly do work externally, but is used to establish a normal working electromagnetic field for electrical equipment (such as transformers and the iron core magnetic field of electric motors), and its unit is Var (volt-amperes reactive) or kvar (thousand volt-amperes reactive).
Functions and Significance
(1)Foundation for equipment operation: Motors and transformers, which are inductive devices, must rely on reactive power to establish a magnetic field and function properly. If there is insufficient reactive power, the equipment cannot establish a sufficient magnetic field, which will lead to decreased efficiency, increased heat generation, and even inability to start.
(2)Key to voltage stability: Reactive power directly affects the voltage of the power grid. When the reactive power of the power grid is insufficient, the line voltage will decrease (especially in long-distance transmission); if there is excessive reactive power, the voltage will increase, and both of these will affect the lifespan of equipment and the stability of the power grid.
(3) Role of generators: Generators can adjust the excitation current output or absorb reactive power to assist in maintaining the stability of the power grid voltage (for example, injecting reactive power into the grid to compensate for the demand of inductive loads).
Definition of Power Factor: Power factor is the ratio of active power (P) to apparent power (S, total circuit power, measured in volt-amps VA), that is, PF = P/S, with a range of 0 to 1.
Functions and Significance
(1)Energy utilization efficiency indicators: The closer the power factor is to 1, the higher the utilization rate of electrical energy (the proportion of active power is high, and reactive power loss is low); if the power factor is too low (such as when the load is mainly inductive), the proportion of reactive power in the apparent power is large, which will lead to additional losses (such as heating) in the lines and equipment.
(2) Economic operation of the power grid: A low power factor will increase the current in the transmission lines, resulting in an increase in line losses (energy loss), and at the same time reduce the actual active power output capacity of generators and transformers (the equipment capacity is occupied by reactive power). Therefore, the power grid usually requires users or generators to maintain a higher power factor, and in necessary cases, measures such as capacitor compensation are needed to increase the power factor.
(3) Generator operation constraints: The power factor of the generator is affected by the combined influence of excitation and active power output. An excessively low or high power factor may cause excessive current in the stator or rotor of the generator, affecting safe operation. Therefore, it needs to be adjusted within the rated range.
The active power is "the energy for doing work", which determines the grid frequency and the power output of equipment; the reactive power is "the energy for generating a magnetic field", which determines the grid voltage and the normal startup and operation of equipment; the power factor is "the indicator of efficiency", reflecting the efficiency of energy utilization and the economic operation level of the grid. The three are interrelated. The generator needs to simultaneously balance the active power output to stabilize the frequency, adjust the reactive power to stabilize the voltage, and maintain a reasonable power factor in order to ensure the safe, efficient and stable operation of the grid.