Expert knowledge for manufacturing companies: How to optimize your three-phase systems and reduce energy losses.
What is reactive power in the three-phase network and why is it relevant for my company?
Reactive power is energy that oscillates in the network between producer and consumer without performing usable work. For your company, this means that lines and transformers are additionally loaded which leads to unnecessary energy costs and potential charges from the energy supplier, especially with a poor power factor.
How does the choice between star and delta connection affect reactive power?
The type of connection for three-phase consumers has a direct impact on power consumption. With the same mechanical load, the power consumption in star connection is a factor of 3 lower than in delta connection. This change in active power also affects the reactive power values and must be taken into account for accurate measurement and the design of compensation systems.
What measurement methods for reactive power are available and which one is suitable for my business?
Common methods include direct measurement with special reactive power measuring devices (often based on DIN 40110-2), the Aron circuit for three-wire systems (measurement with two wattmeters) and the indirect calculation from measured voltage, current, and phase angle. The suitability depends on your specific network characteristics; with non-sinusoidal loads due to modern electronics, advanced power analyzers are usually the better choice for accurate results.
Frequency converters are common in our production. How do they affect reactive power measurement?
Frequency converters and other non-linear consumers produce non-sinusoidal currents, known as harmonics. These lead to the emergence of distortion reactive power (Qd), which is often not accurately captured by conventional measurement methods. Special measuring devices and analyzers are required, which can measure and report these harmonic components and the resulting distortion reactive power precisely.
What are the concrete benefits of reactive power compensation for my company?
Effective reactive power compensation lowers your energy costs by avoiding reactive work fees and reducing energy losses (e.g., losses can be reduced by up to 5%)). Additionally, it relieves your internal network, improves the power factor (cos φ) and can extend the lifetime of your electrical operating equipment such as transformers and motors..
What standards should be considered in reactive power measurement?
The key standards that set calculation methods and definitions for power quantities in electrical networks are DIN 40110-2 (valid in Germany) and the IEEE 1459 (internationally recognized).. Modern measuring devices, such as those from A. Eberle, implement these recognized calculation methods for a standard-compliant measurement.
What is meant by unsymmetrical reactive power and when is its measurement particularly important?
Unsymmetrical reactive power arises from an uneven load on the three phases in the three-phase network. Its measurement is particularly important and meaningful when it occurs directly at the local network transformer or at long supply lines to significantly unsymmetrical loads. This helps to avoid misinterpretations and miscalculations in compensation systems..
How can modern power analyzers support reactive power measurement and analysis?
Modern power analyzers, such as the PQI-DE from A. Eberle, enable a continuous monitoring and detailed analysis of power quality. They can accurately capture various types of reactive power fundamental, harmonic, distortion, modulation, and unsymmetrical reactive power), which is crucial for assessing the effectiveness of harmonic filters and precisely optimizing the entire network.
A precise reactive power measurement in the three-phase network is fundamental to uncover inefficiencies, significantly reducing energy costs by avoiding reactive work fees and increasing overall network stability and efficiency..
Modern industrial facilities with frequency converters and other non-linear loads require advanced measuring technology. This must accurately capture harmonics and the resulting distortion reactive power (Qd) to avoid misdiagnoses and potential oversizing of compensation systems by up to 15%..
Through targeted and correctly dimensioned reactive power compensation, manufacturing companies can significantly improve their power factor (often from values around 0.7 to over 0.95), reduce energy losses in lines and transformers by up to 5%, and the and sustainably extend the lifetime of their electrical operating resources..Discover the secrets of reactive power measurement in three-phase systems. This article shows you how to optimize your systems, reduce costs, and increase efficiency.
Reactive power measurement in three-phase systems is critical for the efficiency of your systems. Understand the basics, measurement methods, and optimization techniques to avoid unnecessary costs and maximize the performance of your systems. Do you need support in optimizing your drive technology? Contact us at Contact!
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Introduction to reactive power measurement in the three-phase network
Die Measuring reactive power enables the optimization of three-phase systems, cost reduction, and sustainable efficiency increases for facilities.
Introduction to the reactive power measurement in the three-phase network
What is reactive power?
Reactive power in the power grid behaves like the foam on a beer: present but without direct benefit. It is a form of electrical energy that oscillates between the producer and consumer without performing usable work, as is the case with an electric motor with a cos φ of 0.7. This reactive energy additionally burdens lines and transformers.
Why is measurement important?
An accurate measurement of reactive power reveals inefficiencies that cause unnecessary energy costs. The measurement and analysis of reactive power, e.g., with power analyzers, is the first step towards optimizing the power factor and avoiding charges from the energy supplier. Understanding and calculating the apparent poweris relevant. For this, precise reactive power measurement in three-phase is essential. Also, inform yourself about the power factor cos phi..Basics of three-phase technology for reactive power measurement
Understanding three-phase systems
A manufacturing company observed an increase in current consumption of about 73% when switching drives from star to delta connection with the same mechanical load, due to different power draws. Understanding how star and delta connections affect voltage, current, and reactive power – with the same load, the power consumption in star connection is a factor of 3 lower than in delta connection – is fundamental.
Voltage and current in the three-phase network
In a typical three-phase network, the voltage between two phases is 400V, and to the neutral conductor, it is 230V. The correct application of these values and the accurate measurement of the phase currents are crucial for the precise calculation of reactive power, e.g., with Q = √3 * U_L * I_L * sin(φ). Measurement errors can lead to inappropriate compensation measures. Information on converting kW to Amperes three-phase is also helpful.
The role of the phase angle
The phase angle φ influences efficiency similarly to synchronicity in rowing: asynchronicity leads to energy loss. A large phase angle between voltage and current results in a high proportion of reactive power and a poor power factor (cos φ), reducing the efficiency of the system, for example, a production line with many motors. The power triangle (S² = P² + Q²) illustrates this relationship: with the same active power P, S increases with increasing Q.Measurement methods of reactive power in the three-phase network
Direct measurement with power meters
Ein metallverarbeitender Betrieb identifizierte durch die Installation spezieller Geräte zur reactive power measurement. Modern devices according to DIN 40110-2 measure reactive power directly by shifting the voltage path by 90° to the consumer voltage. Moderne Geräte gemäß DIN 40110-2 erfassen Blindleistung direkt, indem sie die Spannung am Spannungspfad um 90° zur Verbraucherspannung verschieben. In four-wire systems (e.g., low-voltage networks, U1N = 230V), the total reactive power is the sum of the phase reactive powers: Q = U1N I1 sin φ1 + U2N I2 sin φ2 + U3N I3 sin φ3.
- Modern measuring devices according to DIN 40110-2 allow for direct measurement of reactive power.
- In four-wire systems, the total reactive power is the algebraic sum of the individual phase reactive powers.
- The Aron circuit measures reactive power in three-wire systems with only two wattmeters.
- In the Aron circuit, correct wiring is crucial to avoid sign errors.
- The indirect method calculates reactive power from voltage, current, and phase angle (Q = √3 x V_L x I_L x sin(φ)).
- The indirect calculation is often inaccurate in non-sinusoidal waveforms, e.g., due to frequency converters.
- In non-sinusoidal waveforms, distortion reactive power (Qd) must be considered.
Measurement in three-wire systems (Aron circuit)
With only two wattmeters, the total reactive power in a three-wire system without a neutral conductor can be determined using the Aron circuit. Although the individual measurement values have no direct intuitive meaning, this circuit allows calculation using Q = √3 * (uN3 i1 + u1N i3) using an artificial star point. Correct wiring is necessary to avoid sign errors, especially when φ3 < 30°. Knowledge for calculating the current uptake three-phase motor calculation is helpful here.
Indirect measurement through calculation
A food manufacturer uses the indirect method for initial estimation, measuring voltage, current, and phase angle φ at a frequency converter. Reactive power can be calculated with Q = √3 x V_L x I_L x sin(φ); however, this method is inaccurate for determining reactive power in non-sinusoidal waveforms, such as those produced by frequency converters. In such cases, the distortion reactive power Qd (Qtot = √(Q1² + Qd²)) must be taken into account, which may require specialized analyzers.Challenges and solutions in reactive power measurement
Influence of harmonics
An automotive supplier noted that traditional measuring devices delivered inaccurate values due to the high proportion of electronics and frequency converters in the reactive power analysis , leading to a 15% oversizing of the compensation system. Non-sinusoidal currents and voltages require measuring devices that separately capture and report distortion reactive power (Qd), such as devices from A. Eberle (PQI-DA smart). Distinguishing between different types of reactive power (fundamental frequency, harmonic, distortion, modulation, unbalance) is crucial here.
Unbalanced loads
An uneven phase load, which can occur in factory halls, can distort the measurement results of the reactive power determination . Unbalanced loads, often found with many single-phase consumers, require careful selection of the measurement point – ideally at the local network transformer or at long supply lines to the unbalanced consumers – to obtain meaningful values for the unbalance reactive power. This is a common source of error when planning compensation systems.Importance of reactive power compensation
Objectives of reactive power compensation
A logistics center reduced its annual energy losses by 5% through targeted reactive power compensation, extending the lifespan of its transformers. The main goal is to reduce apparent power and total current, resulting in lower transmission losses (P_V = R_V * I²) and a relief for the grid. The result is an improved power factor close to 1.
- Reduction of apparent power and total current in the grid.
- Minimization of transmission losses (P_V = R_V * I²).
- Relief for lines, transformers, and switchgear.
- Improvement of the power factor (cos φ) towards an ideal value of 1.
- Reduction of energy costs by avoiding reactive power charges.
- Increasing the lifespan of electrical equipment.
- Selection of the compensation method (fixed, dynamic) depending on the load profile.
Improvement of the power factor
A power factor of 0.95 is more advantageous than 0.8, as at 0.95, only about 33% reactive power flows in relation to active power, compared to 75% at 0.8. By means of compensation, for example with capacitor banks, the power factor (cos φ) is improved. This reduces the strain on the grid and is often a prerequisite for cheaper electricity tariffs. The calculation of the compensation capacity C = Q / (ω * U²) is based on the determined reactive power Q. Information on improving the active power factor is relevant.
Methods of reactive power compensation
A steel mill with highly fluctuating loads from arc furnaces uses dynamic reactive power compensation. Fixed installed capacitor banks are suitable for base loads, while variable load profiles require dynamic systems such as thyristor-controlled capacitors (TSC) or static reactive power compensators (SVC) to avoid under-compensation. The correct design, for example with an online product configurator for gear box solutions, is crucial here. The capacitor AC motor.Normative foundations and modern measurement technology
Relevant standards
An internationally active machinery manufacturer must ensure the conformity of its products and measurement methods with global standards. The standards DIN 40110-2 (Germany) and IEEE 1459 (international) define recognized calculation methods for performance quantities, including the determination of reactive power, and form the basis for implementation in modern measuring devices. ATEK Drive Solutions ensures compliance with these standards.
Modern measurement technology
Modern network analyzers enable continuous monitoring and remote querying of relevant network parameters, including various reactive power components. Devices such as the PQI-DE from A. Eberle often offer the ability to differentiate distortion reactive power, which is essential for the assessment of harmonic filters. For industrial networks, a permanent installation at the connection points to the public grid is recommended. The correct implementation of the reactive power measurement in three-phase requires specific knowledge. Information on calculating the capacitor motor is also available.
Precise reactive power measurement. and compensation are important tools for cost reduction and efficiency improvement. Expertise in this area supports the optimization of three-phase systems.
