Reactive power is one of the key factors that has a significant impact on the efficiency of power distribution networks. It is not directly used to perform useful work, but is necessary for the proper operation of inductive loads in the system, such as transformers, motors and inductors. Although these devices require reactive power for their operation, it creates a number of challenges for power systems and results in significant losses in the grid.
Impact of reactive power on electrical systems
When inductive loads in the system use reactive power, it causes an increase in the total current flowing through the grid. This has a number of negative consequences:
- Increased losses in the network: the extra power to be transmitted increases losses in cables and transformers.
- Reduced transformer and cable capacity: Reactive power takes up a fraction of the total network capacity, meaning the system can carry less active power (which is actually useful).
- Voltage instability: Reactive power causes voltage fluctuations, which can lead to instability and unwanted grid failures.
The benefits of reactive power compensation
To minimize these negative effects, modern power grids use reactive power compensation control systems. The main purpose of these systems is to maintain the balance between active and reactive power, improving energy efficiency and grid stability.
Reactive power compensation has the following benefits:
- Reducing network losses: compensation reduces the amount of reactive power that is carried through cables and transformers, resulting in lower energy losses.
- Increasing grid capacity: By compensating for reactive power, the grid can carry more active power, increasing its efficiency and allowing more load without the need for additional infrastructure investment.
- Voltage stabilisation: Maintaining an optimal level of reactive power results in a more stable grid voltage, which improves system reliability.
- Reducing reactive power charges: Many energy suppliers charge for high reactive power use. With proper compensation, these charges can be reduced or avoided altogether.
Types of compensating arrangements and their application
The most common means of reactive power compensation are complete capacitor compensators (CCCs). These consist of capacitors that store and release reactive power, thereby reducing the amount of reactive power the grid must carry. Depending on the specific needs of the users, capacitor banks can be installed at different locations in the grid:
- Central Compensation: this is the most commonly used reactive power compensation system in industrial and commercial applications. In this system, capacitors are installed in the main switchboard and compensate the reactive power of the entire system. Central compensation is easy to maintain and monitor, but cannot compensate for reactive currents occurring within the plants themselves.
- Individual compensation: This method is used in more specific conditions where it is necessary to compensate for the reactive power of individual devices or parts of the network. This is a suitable solution for large energy users, such as electric motors, where reactive power can be significant.
- Group compensation: This technique combines the principles of central and individual compensation by compensating the reactive power of a group of consumers.
Harmonics and their influence on compensating arrangements
Harmonics are nonlinear distortions of electrical signals that occur in the operation of specific electrical devices, such as frequency converters, UPS systems, computers, and other devices that use semiconductor technology. In some cases, the presence of harmonics can cause serious problems for the grid and reduce the effectiveness of compensating devices.
In industrial networks that are contaminated with high levels of harmonics, the use of capacitor banks with built-in reactors is recommended. The reactors prevent the formation of a resonant circuit with the grid inductance, which can cause overload and damage to system components. Depending on the levels of harmonics, reactors with different values are used - most commonly 7% for industrial plants and 14% for office buildings.
Reactive power compensation controllers
The management of the compensation systems is carried out by special controllers that automatically regulate the switching on and off of the capacitors depending on the current reactive power demand. Modern controllers are equipped with sensors and algorithms that monitor network parameters in real time and ensure optimal system operation.
Compensation controllers typically have between 6 and 12 steps, allowing them to respond quickly and precisely to changes in grid load. For plants with many electric motors or other inductive loads, the use of systems with at least 10 steps is recommended to maintain a high power factor.
Selection of a suitable compensation system
When selecting a compensation system, it is important to consider a number of factors, including the reactive power levels to be compensated, the type of network and the presence of harmonics. Energy efficiency specialists perform a network and load analysis to propose the most appropriate solution for each specific case. In addition, compensation systems must be properly sized to ensure optimal performance and long service life of electrical components.
Conclusion
Reactive power compensation is a key element of power system management that not only increases energy efficiency, but also reduces costs and improves grid reliability. Investments in advanced compensation systems pay for themselves quickly and bring significant benefits to consumers while contributing to a more sustainable and efficient use of electricity.
