Reactive power: Overview, definition, and example
What is reactive power?
Reactive power is a component of electrical power that alternates between the source and the load in an AC (alternating current) system but does not contribute to the actual work output, such as running motors or lighting bulbs. Instead, it is the power that oscillates back and forth, required to maintain the magnetic fields in inductive loads like motors, transformers, and inductors. Reactive power is measured in volt-amperes reactive (VARs) and is an essential part of the overall power in an electrical system, even though it does not directly do useful work.
In an AC system, the total power is made up of two components: active (real) power, which does the actual work, and reactive power, which helps sustain the magnetic fields needed for operation. The total power is referred to as apparent power, measured in volt-amperes (VA), and is the combination of both active and reactive power.
Why is reactive power important?
Reactive power is important because it supports the voltage levels in an electrical system, allowing current to flow efficiently to loads such as electric motors, lights, and other equipment. Without adequate reactive power, electrical equipment could experience voltage drops, leading to reduced efficiency, power outages, or damage to sensitive equipment.
For power grid operators, managing reactive power is crucial for maintaining the stability and reliability of the grid. It helps to regulate voltage, optimize power delivery, and prevent overloading of electrical equipment. While reactive power doesn't do direct work, it plays a vital role in the functioning of the entire power system.
Understanding reactive power through an example
Consider an industrial facility that uses several large motors. These motors are inductive loads, which require reactive power to build and sustain their magnetic fields. While the motors are consuming active power to perform their tasks (e.g., running machinery), they also require reactive power to maintain operation. This reactive power does not contribute to the work output but ensures the motors can continue running efficiently.
If the facility’s power system is not properly managing reactive power, it may result in voltage fluctuations or low voltage conditions that can cause the motors to perform poorly, overheat, or even stop functioning. To prevent this, capacitors or other devices that supply reactive power are often installed to support the system and stabilize the voltage.
In another example, when you turn on a fluorescent light, it requires both active and reactive power to function. The active power is used to generate light, while the reactive power helps maintain the operation of the ballast that regulates the flow of current to the light.
An example of a "reactive power" clause
Here’s how a reactive power clause might appear in an electricity supply agreement:
“The customer agrees to maintain a power factor of at least 0.95, and the supplier will provide the necessary reactive power compensation to ensure stable voltage levels and efficient operation of the customer’s electrical equipment. If the customer’s reactive power demand exceeds the agreed-upon limits, additional charges may apply to compensate for the increased load on the grid.”
Conclusion
Reactive power is an essential component of the electrical power system that supports voltage regulation and helps sustain the magnetic fields in inductive loads. While it does not perform useful work like active power, its role is vital in ensuring the stability, efficiency, and reliability of electrical systems. Proper management of reactive power is crucial for both grid operators and consumers to prevent equipment damage, voltage instability, and power inefficiency.
This article contains general legal information and does not contain legal advice. Cobrief is not a law firm or a substitute for an attorney or law firm. The law is complex and changes often. For legal advice, please ask a lawyer.