Reactive power – what it is and how to address issues related to its consumption
In large enterprises, where every kilowatt-hour of energy counts, managing energy efficiency is one of the most critical actions in achieving sustainable development and gaining a competitive advantage — especially in energy-intensive industries. One of the key, yet often overlooked, aspects is reactive power. Understanding this concept and managing it effectively can bring significant financial and operational benefits to industrial companies.
What is reactive power?
Reactive power is the energy necessary to maintain the operation of power systems, but it is not converted into useful work, such as mechanical or thermal energy. Reactive power (Q) is the part of electric power that flows between the energy source and the load without performing useful work. The unit of reactive power is var – Volt Ampere Reactive.
How to calculate reactive power?
We distinguish between inductive and capacitive reactive power depending on the receiving device. Reactive power causes additional load on the power grid – charges are applied for its consumption to encourage users to reduce its amount. It affects the capacity of the distribution network and can have negative effects, causing failures and overloads. Effective management of reactive power is a solution that helps reduce additional charges and improves voltage stability in the electrical system.
The coefficient used by operators to settle accounts for the consumption of inductive reactive power is tgφ. In most cases, its level must not exceed 0.4 (for areas with technically weaker infrastructure, the coefficient is even more restrictive). This means that consuming more than 40 kvarh of reactive power per 100 kWh of active power results in additional charges.
Where does reactive power come from?
Reactive power results from the presence of reactive components in electric circuits:
Inductive reactive power (L) is generated by devices with inductive components that store energy in a magnetic field. Examples include induction motors, transformers, transmission lines, lighting systems, induction furnaces, or chokes. This type of reactive power causes a lagging phase shift of current in relation to voltage.
Capacitive reactive power (C) is generated by devices with capacitive components that store energy in an electric field. Examples include computers, welding machines, inverters, live cables, UPS systems, or damaged capacitor banks. This type of reactive power causes a leading phase shift of current in relation to voltage.
How can reactive power be reduced?
The most common method of managing reactive power is reactive power compensation. It involves using devices that can neutralize excess reactive power, such as:
- Capacitors – used to compensate inductive reactive power.
- Chokes – used to compensate capacitive reactive power. An important issue is the correct selection of the power and individual steps of the reactive power compensation system to avoid undercompensation or overcompensation. It is advisable to carry out appropriate measurements.
Modern electrical devices often include built-in reactive power management systems, which allow for more efficient energy use. Investing in such devices can significantly reduce the amount of generated reactive power. It is also possible to optimize the operation of inductive and capacitive devices. An example would be synchronizing the operation of large electric motors to minimize the generation of reactive power.
Another solution is advanced energy monitoring and control systems that can help identify sources of reactive power and optimize their operation. These systems automatically control compensation devices in real-time. For dynamic changes in reactive power, one may also consider the use of an advanced active compensator (SVG) based on thyristors.
Why reduce reactive power?
- Financial savings – reducing reactive power can significantly lower electricity bills, as many energy tariffs include additional charges for excessive reactive power drawn from the grid.
- Increased energy efficiency – effective reactive power management increases the overall energy efficiency of a facility, leading to lower operating costs.
- Reduced risk of grid overload – reducing reactive power decreases the load on the power grid, helping prevent overloads and failures.
- Improved stability of the electrical system – effective reactive power management improves voltage stability in the electrical system and is key to the proper operation of devices.
- Increased equipment lifespan – optimizing reactive power reduces the risk of overheating and damage to electrical equipment.
Summary
Reactive power is an important, though often overlooked, element of energy efficiency management. Effective reactive power management – through compensation, use of modern devices, and process optimization – can bring significant financial and operational benefits. If a company incurs costs of at least PLN 500 net per month for non-contractual consumption of inductive or capacitive reactive power and these are recurring charges, reducing its consumption will be a good solution for the enterprise. Typically, taking such action results in immediate savings and is characterized by a very short payback period – often under half a year.
Thinking about a company’s energy efficiency begins with examining internal processes, taking measurements, and reducing unnecessary energy drawn from the grid.
