Difference between Reactive Power and Resistance Power

Reactive power and resistive power (real power) are two fundamental but distinct concepts in a power system. They describe different aspects of the energy storage and conversion processes within a power system.

1. Definition and Physical Meaning

Reactive Power refers to the power generated when current flows through a capacitor or inductor in an AC circuit. It does not perform any actual power conversion or energy transfer but is used to compensate for the reactive power required by capacitors and inductors in a circuit. The unit of reactive power is usually VAR (Volt-Ampere Reactive) or kVAR (kiloVolt-Ampere Reactive). It is calculated based on virtual power, which is related to the phase difference between current and voltage, representing the ability to flow and store electrical energy.

Resistive Power, also known as real power, refers to the amount of alternating current energy that is actually generated or consumed per unit time. It is the average power over a period and is typically measured in watts (W) or kilowatts (kW). Real power describes how electrical energy is converted into other forms of energy, such as heat, mechanical energy, etc.

2. Calculation Formula

The formula for calculating reactive power is:

Q = I × U × sin φ 

In it,  $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;"><br></span>}$I is the current,  $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;"><br></span>}$U is the voltage, and  $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;">\varphi is\; the\; phase\; angle\; between\; the\; voltage\; and\; the\; current.</span>}$

The formula for calculating resistance power (active power) is:

P = I × U × cos φ

Likewise,  $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;">I is\; the\; current, </span>}$ $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;">U is\; the\; voltage,\; and </span>}$ $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;">\varphi is\; the\; phase\; angle\; between\; the\; voltage\; and\; the\; current.</span>}$

3. Functions and Applications

Reactive power plays an important role in the power system. It is one of the main parameters for calculating the total power factor of the circuit, determining the size of the power factor and telling us about the storage and transmission of energy in the circuit. Reactive power is also used for reactive compensation in power systems, improving the power factor and effective utilization of electrical energy by adjusting capacitors and inductors in the circuit.

Resistive power (real power) is the electrical energy that is actually consumed, and it describes how electrical energy is converted into other forms of energy, such as thermal energy, mechanical energy, etc. In a power system, real power is an important indicator for measuring the consumption and supply of electrical energy.

4. Units and Symbols

The unit of reactive power is the volt-ampere reactive (VAR) or kilovolt-ampere reactive (kVAR), represented by the symbol  $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;">Q.</span>}$

The unit of resistance power (real power) is in watts (W) or kilowatts (kW) and is represented by the symbol  $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;">P.</span>}$

Conclusion

Reactive power and resistive power (real power) are two fundamental concepts in a power system, each describing different aspects of the energy storage and conversion processes within the system. Reactive power focuses on the flow and storage of electrical energy, while resistive power (real power) concerns itself with the actual consumption and conversion of electrical energy. Understanding the distinction between these two is crucial for the analysis and design of power systems.