In the present world, the quality and reliability of electrical power supply systems have become more crucial than before. It is essential to maintain high power quality because reliance on electronics and intricate industrial equipment is growing much faster. However, one of the key challenges in implementing this goal is handling the levels of harmonics in the power system. Harmonics involve voltage or current waveforms with frequencies in integer multiples of the fundamental frequency and disturb the actual sinusoidal waveform of the electrical power. This distortion can cause many problems, such as loss of efficiency, equipment overheating, system failure, etc.
Engineers and technicians maintaining stable and effective power systems must understand and analyse harmonics. This blog focuses on the basics of harmonic analysis, including what harmonics are, what causes them, and how they affect electrical equipment. We will then describe the techniques for detecting and controlling harmonics and the available norms. Whether you are an experienced engineer or a fresh graduate, this study on harmonic analysis will give insight into one of the critical parameters in electrical power systems.
Understanding Harmonics in Electrical Power Systems
Electrical power systems in harmonics are voltage or current waveforms that occur out of phase with the fundamental frequency by a multiple of an integer. Generally, the primary frequency in most power systems is either 50 Hz or 60 Hz, depending on the region.
Non-sinusoidal current or voltage waveform is distorted mainly by non-linear loads, which creates harmonics. These non-sinusoidal loads develop other frequencies that reside on the fundamental frequency, giving it a distorted sinusoidal waveform. Harmonics can be classified by their order: the second harmonic is twice the fundamental frequency, the third harmonic is three times, and so on.
The first or base harmonic in most power systems is 50 Hz or 60 Hz, which is the primary frequency of the power system. It is the desired sinusoidal waveform used to transfer power and control the function of electrical apparatus.
However, these include the higher odd multiples of the fundamental frequency harmonics. The fundamental frequency guarantees an optimal smooth running of electrical equipment. At the same time, the current harmonics introduce distortions that can lead to inefficiencies and potential damage.
What causes Harmonics?
Harmonics are mainly produced by non-linear loads that draw current in a nonsinusoidal way, although supplied with sinusoidal voltage. Some common sources of harmonics include:
- Non-linear loads: These include a computer, a printer, and fluorescent lighting that draws pulse currents rather than sinusoidal forms.
- Electronic devices: Power electronic devices such as rectifiers, inverters, and variable frequency drives (VFDs) that convert AC to DC and vice versa.
- Industrial equipment: Industries where heavy machinery, such as arc furnaces, heavy tools, or welding tools, is present.
These sources modify the current waveform, changing the voltage waveform across the power system and introducing harmonic distortion.
Harmonic order is one of the most essential concepts in harmonics, and it deals with describing the phenomena and effects of harmonics. It is defined as the ratio of the harmonic frequency to the fundamental frequency. Harmonics of a different order generally make different impacts on the power system. Subharmonics of lower orders (like the third or the fifth) are usually more problematic because their amplitudes are much higher and have more significant impacts, such as heating and resonance issues.
The higher-order harmonics, though, are of lesser amplitude; nonetheless, they can still contribute to distortion and inefficiency in the system. Understanding the harmonic order helps you design mitigation strategies and implement filters to minimise their adverse effects on the power system.
Effect of Harmonics on Electrical Equipment
Harmonics affect electrical equipment in various ways, including efficiency, reliability, and endurance. The primary concerns include overheating. All kinds of harmonics cause an increase in the RMS value of the current. This increases heat in transformers, motors, or conductors and affects modern adjustable-speed drive systems.
This overheating could lead to insulation failure, decreasing the operational life of the equipment in use. Harmonic torque pulsations also create mechanical vibration and audible noise due to the harmonic torque pulsations, which exert mechanical stress on the motor.
Moreover, protective devices such as relays and circuit breakers may misoperate in the presence of harmonics, resulting in false tripping or a failure to trip during actual fault conditions. Another considered problem is resonance, which occurs when such harmonics resonate with natural frequencies of operating power system elements, and causes increased voltage and current values that entail severe impact.
Electronic devices sensitive to EMI may get affected by the harmonics and hence get damaged. Lastly, the harmonics affect additional losses in the power distribution system, resulting in decreased efficiency and high costs.
Methodology
Conducting a harmonic analysis involves several steps to identify, measure, and mitigate harmonics in a power system:
- Data Collection: Acquire information about the layout of the power system, the kind of loads, and the working environment.
- Measurement: Measure the system’s harmonic content using harmonic analysers or power quality meters. Some of the main parameters are Total Harmonic Distortion (THD) and the magnitude of particular harmonics.
- Modelling: Develop the power system model using any power system analysis tool such as ETAP, MATLAB, or PSCAD to analyse the harmonic source and impact.
- Analysis: Perform harmonic analysis on the currents and voltages to determine which harmonics are bad for the system. This includes finding the total harmonic distortion, which is compared with the permissible level.
- Mitigation: Conduct risk analyses to address harmonic issues and introduce the methods of passive filters, active filters, and hybrid filters, as well as revisions of the product or system equipment or changes in operating modalities.
- Verification: Re-measure harmonics after all treatments to confirm that the proposed solutions effectively reduce harmonics and comply with standards.
Harmonics Measurement Standards
Several standards provide guidelines for measuring and controlling harmonics in electrical power systems:
- IEEE 519: This standard is for electrical systems, and its guidelines state the maximum allowable harmonic distortion and practices for controlling them.
- IEC 61000-3-2 and IEC 61000-3-4: These standards limit the harmonic current produced by the equipment connected to the public low-voltage and medium-voltage systems.
- EN 50160: This European standard outlines various parameters of the voltage delivered by public distribution systems, harmonics inclusively.
Harmonic Analysis by Ocean
Ocean provides customers with reliable and enhanced harmonic analysis. They effectively and methodically use the latest tools and experience to search undesired electrical currents (harmonics) produced by complex equipment, which could affect power flow and electrons’ efficiency. They will define the contaminant sources and quantify such disruption effects. After harmonics are identified, a perfect approach to combating them shall be implemented, guaranteeing the efficiency of the systems at your disposal.
Being the leading engineering company in Oman, Ocean takes you through the setup process of your system concerning the existing electrical codes and standards, irrespective of the level of complications involved. We offer condition monitoring services like partial discharge testing, laser shaft alignment, vibration analysis, and much more. Ensure the safety of your machines with Ocean.