Table of Contents
What Is Reactive Power?
Reactive power is a term used in electrical engineering that refers to the power consumed by reactive components in an alternating current (AC) circuit. In an AC circuit, the current and voltage may not be in phase due to the presence of reactive components like inductors and capacitors. This phase difference between the current and voltage leads to the concept of reactive power.
Reactive power is necessary for the establishment of electromagnetic fields in inductive and capacitive elements. It does not perform any actual work but is required for the magnetic and electric fields to properly function. While it does not contribute to the net power transfer in the circuit, it affects the overall power factor of the system.
Reactive power is typically measured in voltamperes reactive (VAR) and is an important concept in power engineering for the design, operation, and control of power systems.
What Causes Reactive Power?
Reactive power arises in AC circuits due to the presence of reactive elements such as inductors and capacitors.
These components store and release energy periodically as the current and voltage fluctuate. The specific causes of reactive power are as follows:

Inductors: Inductors are passive electrical components that store energy in the form of a magnetic field when a current flows through them. When the current changes, the magnetic field collapses, releasing the stored energy back into the circuit. This results in a phase shift between the voltage and current, leading to reactive power.

Capacitors: Capacitors store energy in the form of an electric field when a voltage is applied across them. Similar to inductors, when the voltage changes, the electric field collapses, releasing the stored energy back into the circuit. This also results in a phase shift between the voltage and current, contributing to reactive power.
In practical electrical systems, reactive power is also influenced by various factors such as the presence of electric motors, transformers, transmission lines, and other components that introduce impedance and phase shifts in the system. These factors collectively lead to the consumption of reactive power in the circuit.
Explaining Reactive Power
Power in an electrical circuit is the result of multiplying the voltage (V) and current (I). In the case where either the voltage or current becomes zero, the power also becomes zero. When dealing with an AC circuit involving components like capacitors or inductors, a 90degree phase shift is always present.
This phase shift implies that the power value is zero when either the voltage or current has a zero value. Essentially, this suggests that although the source generates power, the load does not utilize it, creating an undesirable condition known as reactive power.
Reactive power is sometimes referred to as phantom power, wattless power, or useless power. It is symbolized by Q and is measured in VoltAmperes Reactive (VAR) or Kilo VoltAmperes Reactive (KVAR).
Understanding and managing reactive power is crucial for maintaining efficient power usage in electrical systems.
reactive power formula
We can use the power factor triangle to memorize the power factor, reactive, apparent, and active power formulas.
The formula for a single phase:
The formula for singlephase Reactive Power is Q = V x I x SinΦ
Where
 $Q$ is the reactive power in voltamperes reactive (VAR),
 V is the voltage in volts (V),
 I is current in amperes (A), and
 ϕ is the phase angle between the voltage and current.
The formula for threephase:
The formula for threephase Reactive Power is Q = 1.732 x Vx I x sin φ
Other shapes of the formula:
Reactive Power Q= √ (S^{2 }– P^{2}), While S is apparent power & P is active power.
In an AC circuit, the phase angle ϕ represents the phase difference between the voltage and current waveforms. The sine of this phase angle indicates the portion of the apparent power that is reactive.
The reactive power is the component of the apparent power that does not perform any actual work but is necessary for establishing and maintaining electromagnetic fields in reactive elements such as inductors and capacitors.
importance of reactive power in the power system
Reactive power plays a critical role in power systems and has several important implications for the efficient and reliable operation of electrical grids. Some key points highlighting the importance of reactive power are:

Voltage Control: Reactive power is vital for regulating and maintaining voltage levels within acceptable limits. It helps to stabilize the voltage profile across the transmission and distribution networks, ensuring that electrical devices and equipment receive the required voltage for proper operation.

Power Factor Correction: Managing reactive power is crucial for improving the power factor, which is the ratio of real power to apparent power. A poor power factor can lead to increased system losses, reduced efficiency, and higher energy costs. By controlling reactive power, power factor correction devices can improve the efficiency of the power system and reduce electricity expenses for consumers and utilities.

Line Loss Reduction: Managing reactive power can help in reducing resistive losses in transmission and distribution lines. By optimizing the power factor and minimizing reactive power flow, the overall line losses can be reduced, leading to a more efficient and costeffective operation of the power system.

Increased Transmission Capacity: Proper management of reactive power can enhance the transmission capacity of power lines and cables. By minimizing reactive power flow, more active power can be transmitted through the existing infrastructure, improving the overall capacity and reliability of the power system without the need for costly upgrades.

Stability and Reliability: Maintaining an appropriate balance of reactive power is essential for ensuring the stability and reliable operation of the power grid. Uncontrolled reactive power can lead to voltage fluctuations, voltage collapses, and other stability issues that may result in system outages and blackouts.

Equipment Performance: Reactive power control helps in ensuring the optimal performance of electrical equipment, including motors, transformers, and other industrial machinery. By managing reactive power, the stress on the equipment is reduced, leading to improved performance, increased lifespan, and decreased maintenance costs.
The management and control of reactive power are crucial for maintaining the stability, efficiency, and reliability of power systems, ultimately contributing to the overall economic and operational performance of the electrical grid.
How does reactive power regulate the voltage of a power system?
Reactive power plays a crucial role in regulating the voltage of a power system. Here’s how it helps maintain stable voltage levels:

Voltage Support: Reactive power helps to support and stabilize the voltage in the system by compensating for voltage drops that occur due to the impedance of the transmission and distribution lines. By injecting or absorbing reactive power, voltage levels can be maintained within acceptable limits, ensuring that electrical devices and equipment receive the required voltage for proper operation.

Voltage Control Devices: Various voltage control devices such as capacitors and reactors can be strategically placed in the power system to generate or absorb reactive power. Capacitors inject reactive power into the system, raising the voltage, while reactors absorb reactive power, thereby lowering the voltage. These devices are controlled based on the system’s voltage requirements, helping to regulate and stabilize the voltage profile.

Power Factor Correction: Managing reactive power is essential for power factor correction, which is the ratio of real power to apparent power. By maintaining a power factor close to unity (1), the voltage fluctuations are minimized, leading to stable voltage levels throughout the system. Power factor correction devices such as capacitors are used to improve the power factor, consequently aiding in voltage regulation.

Voltage Stability: Reactive power control contributes to voltage stability by ensuring that voltage variations caused by changes in load demand, network configuration, or other factors are minimized. By actively managing the flow of reactive power, voltage fluctuations are reduced, enhancing the overall stability of the power system and preventing voltage collapses or instability issues.
Overall, the regulation of reactive power in the power system is crucial for maintaining stable and reliable voltage levels, ensuring the efficient operation of electrical devices, and preventing potential voltagerelated problems such as undervoltage or overvoltage conditions that could lead to equipment damage or power disruptions.
How To Reduce Reactive Power In AC Power Systems?
Reducing reactive power in AC power systems is important for improving the power factor and overall efficiency of the system. Several methods can be employed to achieve this:

Power Factor Correction (PFC) Capacitors: Installing capacitors at strategic points in the system can compensate for the reactive power demand, thus reducing the overall reactive power flow. This method is known as power factor correction and is one of the most common ways to minimize reactive power in an AC power system.

Synchronous Condensers: Synchronous condensers are rotating machines that generate or absorb reactive power. They can be used to provide the necessary reactive power support, thereby reducing the overall reactive power flow in the system. Synchronous condensers are often employed in power systems to stabilize voltage and improve the power factor.

Static Var Compensators (SVCs): SVCs are power electronicsbased devices used to regulate voltage and minimize reactive power in AC systems. They can quickly and precisely control the reactive power output, thereby improving the power factor and reducing the reactive power flow in the system.

PhaseShifting Transformers: Phaseshifting transformers can be used to control the flow of reactive power in the system by adjusting the phase angle between different parts of the power grid. By managing the phase angle, the reactive power flow can be optimized, leading to improved power factor and reduced losses.

HighEfficiency Motors and Equipment: Using highefficiency motors and equipment with power factor correction capabilities can help reduce the reactive power demand in the system. These devices are designed to operate more efficiently, thereby minimizing the reactive power consumption and improving the overall power factor.

Load Balancing and Load Shedding: Proper load balancing and shedding can help minimize the reactive power demand in the system. By distributing the load evenly and shedding nonessential loads, the overall reactive power requirement can be reduced, leading to improved power factor and increased system efficiency.
Implementing these strategies can help reduce the reactive power demand in AC power systems, leading to improved power quality, increased energy efficiency, and reduced operational costs.
Read also My Article What is Power factor correction?
What Is The Reactive Power Compensation?
Reactive power compensation refers to the process of managing and correcting the reactive power in an electrical system to improve the power factor and overall efficiency.
The objective of reactive power compensation is to minimize the reactive power flow and optimize the power factor, thereby enhancing the performance and stability of the power system.
Reactive power compensation is essential for maintaining stable voltage levels, reducing power losses, and ensuring the efficient operation of the electrical grid.
By implementing appropriate compensation techniques, utilities and industries can enhance the reliability and performance of the power system, leading to improved energy efficiency and cost savings.
What Are The Advantages Of Reactive Power Compensation?
Reactive power compensation offers several advantages that contribute to the improved efficiency, stability, and performance of power systems. Some of the key benefits include:

Improved Power Factor: One of the primary advantages of reactive power compensation is the enhancement of the power factor. By minimizing the reactive power flow and increasing the proportion of real power in the system, the power factor is brought closer to unity (1), resulting in improved energy efficiency and reduced power losses.

Stable Voltage Levels: Reactive power compensation helps to stabilize voltage levels within acceptable limits, ensuring that electrical devices and equipment receive the required voltage for optimal performance. By regulating the voltage, the risk of voltage fluctuations and voltagerelated issues is minimized, leading to enhanced system reliability.

Reduced Transmission Losses: By managing reactive power flow, the overall transmission and distribution losses in the power system can be reduced. Minimizing reactive power consumption leads to lower line losses and improved energy efficiency, ultimately resulting in cost savings and reduced environmental impact.

Increased Transmission Capacity: Effective reactive power compensation can improve the transmission capacity of power lines and cables. By optimizing the power factor and voltage levels, more active power can be transmitted through the existing infrastructure, enhancing the overall capacity and reliability of the power system without the need for significant upgrades.

Enhanced Equipment Performance: Proper reactive power compensation helps to reduce the stress on electrical equipment, including motors, transformers, and other industrial machinery. This leads to improved equipment performance, increased lifespan, and reduced maintenance costs, resulting in improved overall system reliability.

Compliance with Regulatory Standards: Implementing reactive power compensation enables compliance with regulatory standards related to power factor requirements. Adhering to these standards ensures the efficient and reliable operation of the power system and avoids penalties associated with poor power factor performance.
Overall, reactive power compensation offers substantial benefits that contribute to the efficient and reliable operation of power systems, leading to cost savings, improved equipment performance, and a more sustainable energy infrastructure.
Can Reactive Power Be Negative?
Reactive power can indeed be negative in some situations, especially in systems with certain types of loads and power generation.
When the reactive power supplied is greater than the reactive power consumed, the excess reactive power can be considered as negative reactive power.
In power systems, negative reactive power is often associated with capacitive loads or devices that generate reactive power.
Capacitive loads, such as capacitors, produce reactive power that leads the voltage and current to be out of phase, creating a leading power factor. This can result in an apparent ‘negative’ reactive power when considering the overall power flow in the system.
Negative reactive power can have implications for power factor correction and voltage control strategies. Proper monitoring and management of negative reactive power are essential to ensure stable voltage levels and an efficient power factor in the system.
Power factor correction devices and control mechanisms may need to be adjusted to account for negative reactive power contributions and maintain the stability and reliability of the power system.
Which Is Greater Reactive or Active Power?
The comparison between reactive power (Q) and active power (P) doesn’t imply that one is necessarily greater than the other, as they represent different aspects of the power in an electrical system.
Active power (P) is the actual power that is consumed or produced and is the component of power that performs useful work. Reactive power (Q), on the other hand, is the power that does not perform any useful work but is required for the establishment of electromagnetic fields in inductive and capacitive elements.
These two components, along with the apparent power (S), form what is known as the power triangle in electrical engineering. The relationship between active power, reactive power, and apparent power is represented mathematically as:
S^{2}=P^{2}+Q^{2}
Where S is the apparent power, P is the active power, and Q is the reactive power.
While the magnitudes of reactive power and active power can be different, they are both crucial in understanding the behavior and characteristics of electrical systems. Maintaining an optimal balance between them is important for ensuring the efficient and reliable operation of the power system.
For more information read my article, Apparent, Real and Reactive Power
Why Do We Call Reactive Power Useless?
Reactive power is sometimes referred to as “useless” or “wasted” power because it does not perform any useful work in terms of providing energy for enduse applications. Unlike active power, which is responsible for producing the actual work and performing tasks such as heating, lighting, or mechanical work, reactive power does not contribute to these direct functionalities. Instead, it is necessary for establishing and maintaining the electromagnetic fields in inductive and capacitive elements.
The term “useless” can be somewhat misleading, as reactive power is essential for the proper functioning of electrical equipment and power systems. It is required for the operation of devices such as motors, transformers, and other inductive or capacitive loads. Without reactive power, these devices would not be able to operate efficiently, leading to issues such as decreased motor torque, increased power losses, and reduced voltage stability.
While reactive power is not directly consumed by the enduse equipment, its management is crucial for maintaining the stability and efficiency of the power system. Measures such as power factor correction and reactive power compensation are employed to minimize the impact of reactive power on the overall system performance. By managing reactive power effectively, utilities and industries can improve the power factor, reduce energy losses, and enhance the overall reliability of the electrical grid.
Do generators produce real or reactive power?
Generators produce both real power and reactive power, as they are responsible for supplying electrical energy to the power system.
The combination of these two components forms the concept of apparent power, which is the vector sum of real power (P) and reactive power (Q).

Real Power (P): Generators produce real power, which is the actual power that performs useful work and is consumed by electrical devices and equipment. Real power is measured in units of watts (W) or kilowatts (kW) and is responsible for tasks such as providing mechanical work, heat, or light.

Reactive Power (Q): Generators also produce reactive power, which is necessary for establishing and maintaining the electromagnetic fields in inductive and capacitive elements within the power system. Reactive power does not perform any actual work but is crucial for the efficient operation of devices such as motors, transformers, and other reactive loads.
The overall power output of a generator, or its apparent power (S), is the combination of both real power and reactive power, represented mathematically as:
S^{2}=P^{2}+Q^{2}
Generators are designed to provide a balanced combination of real and reactive power to ensure the stable and reliable operation of the power system. Maintaining an optimal balance between these two components is essential for enhancing the efficiency and performance of the electrical grid.
How To Control The Reactive Power Of A Generator?
Controlling the reactive power of a generator is crucial for maintaining the stability and efficiency of the power system. Several methods and devices can be employed to manage and regulate the reactive power output of a generator:

Automatic Voltage Regulators (AVRs): Automatic Voltage Regulators are used to control the generator’s terminal voltage by adjusting the field excitation. By regulating the excitation level, AVRs can effectively control the reactive power output of the generator, ensuring that the voltage remains within acceptable limits.

Synchronous Condensers: Synchronous condensers are rotating machines that can be controlled to provide or absorb reactive power as needed. They are often used to improve the power factor and stabilize the voltage in the power system. By adjusting the excitation of synchronous condensers, the reactive power output of the generator can be controlled.

Static Var Compensators (SVCs): SVCs are solidstate devices used for fast and precise control of reactive power. They can be connected to the generator terminals to regulate the reactive power output and stabilize the voltage, particularly during fluctuations in the system load.

Power Factor Correction Capacitors: Installing power factor correction capacitors at the terminals of the generator can help improve the power factor and control the reactive power output. Capacitors supply reactive power, thereby reducing the burden on the generator to produce reactive power, leading to improved overall efficiency.

Generator Control Systems: Modern generator control systems are equipped with advanced control algorithms that can monitor and adjust the generator’s reactive power output in real time. These systems utilize sophisticated control strategies to maintain the desired power factor and voltage levels within the power system.
By implementing these control measures, operators can effectively manage and regulate the reactive power output of generators, ensuring the stability, efficiency, and reliable operation of the power system.
Can Reactive Power Affect The Power Factor?
Reactive power is directly related to the power factor of an electrical system. In fact, the presence of reactive power significantly influences the power factor, which is a measure of the efficiency of the power utilization in the system.
 Power Factor and Reactive Power: The power factor (PF) is the ratio of real power (P) to the apparent power (S) in an AC electrical system. Mathematically, it can be represented as the cosine of the phase angle (cos φ) between the voltage and current waveforms. The power factor is a crucial indicator of how effectively the current is being converted into useful work.
 Effect of Reactive Power: In the presence of reactive power, the power factor tends to decrease. This happens because the reactive power introduces a phase shift between the voltage and current, resulting in a lagging power factor. A lower power factor indicates that a significant portion of the apparent power is not effectively utilized to perform useful work.
 Power Factor Correction: Managing reactive power is essential for power factor correction, which involves minimizing the reactive power flow to improve the power factor. Power factor correction devices such as capacitors are employed to offset the effects of reactive power, thereby increasing the power factor and improving the overall efficiency of the power system.
 Efficiency and System Losses: A low power factor can lead to increased system losses, higher currents, and decreased voltage levels. This can result in reduced efficiency, increased energy costs, and potential damage to electrical equipment.
Effectively managing and controlling the reactive power in the system is critical for maintaining a high power factor, ensuring efficient power utilization, and minimizing energy losses. By implementing power factor correction measures, utilities and industries can improve the power factor and enhance the overall efficiency and performance of the electrical grid.
Read my article for more information about Power Factor.
True / Actual Power vs. Reactive Power?
Active power  Reactive power 
Active power is the power that is used to do the actual work. To run a motor, light up a bulb, and charge a battery, etc.  Reactive power is not used but is employed to use the phenomenon of induction. Without reactive power, products like transformers would not be able to work. 
It is dissipated in resistive components.  It is dissipated in reactive components. 
It is denoted by “P”.  It is denoted by “Q”. 
It is measured in Watts[W].  It is measured in VoltAmperes [VA]. 
In AC circuits, it flows in a direction with a frequency.  In AC circuits, it does not flow but it makes the electrons move back and forth about a mean position. 
It cannot produce magnetism.  It produces magnetism. 
P= I^{2}R [W]  Q= I^{2}X [VA] 