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What is Harmonic Study and Analysis?
A harmonic study in an electrical system is an analysis focused on identifying and understanding the presence and impact of harmonics within the system.
What is Harmonic?
Harmonics in electrical systems refer to voltages or currents that operate at frequencies that are integer multiples of the fundamental frequency of the system (the primary frequency of the power supply, which is typically 60 Hz in North America and 50 Hz in many other parts of the world). These higher-order frequencies are generated by non-linear loads, which are electrical devices or equipment that cause the current to flow in a manner that does not directly correspond to the voltage.
What Generates Harmonics?
Harmonics in electrical systems are primarily generated by non-linear loads, which are devices that draw current in a non-sinusoidal manner. These include a wide range of modern electronic devices and electrical equipment, such as:
Used to control the speed of motors in HVAC systems, pumps, and conveyors, VFDs adjust the frequency and voltage supplied to the electric motor, resulting in non-linear current draw.
Found in computers, office equipment, telecommunications equipment, and many consumer electronics, SMPS convert electrical power efficiently but generate harmonics due to their switching actions.
While energy-efficient, LED drivers often use rectifiers and switching elements that can introduce harmonics into the electrical system.
Like LEDs, the electronic ballasts in CFLs can generate harmonics.
Used for emergency power to loads when the input power source fails, UPS systems can introduce harmonics due to their internal switching circuits.
The nature of the welding process, particularly with arc welders, results in a non-linear load that generates significant harmonics.
These are used in a variety of applications, including battery charging and DC motor drives, and can generate harmonics due to their rectification process.
Especially those used in industrial processes, where the method of heating involves power electronics that can distort current waveforms.
Used in cooking and industrial processes, these devices can produce harmonics due to the high currents and rapid switching involved.
These devices convert DC to AC and can introduce harmonics into the grid, especially if not properly designed or filtered.
What Effects Do Harmonics Produce?
Harmonics in electrical systems can produce a variety of undesirable effects that can impact both the performance and longevity of electrical equipment, as well as the quality of power within the system. Here are some of the key effects harmonics can produce:
Harmonic currents can cause excessive heating in electrical equipment such as transformers, motors, and cables. This is due to the increased losses in these devices when operating under non-linear loads, which can reduce their efficiency and lifespan.
Sensitive electronic equipment may malfunction or fail prematurely when exposed to harmonic distortion. This is because many electronic devices are designed to operate with a clean sinusoidal power supply, and the distorted waveforms can interfere with their operation.
Harmonic currents do not contribute to the useful power of the system but do increase the total current flowing through electrical infrastructure. This can lead to the overloading of cables and transformers, potentially causing equipment damage or failure.
Power factor correction capacitors can be particularly vulnerable to damage from harmonics. The capacitors can resonate with harmonic frequencies, leading to excessive voltages and currents that can cause capacitor failure or reduce their effective lifespan.
Harmonic currents can cause circuit breakers to trip more frequently, even if the load appears to be within normal limits. This nuisance tripping is due to the extra heat and magnetic effects generated by harmonics, which can affect the operation of protective devices.
Harmonics can lead to higher energy losses in the system, which not only affects the efficiency of power delivery but can also lead to increased energy costs.
Harmonics can cause interference in telephone lines and data communication systems. The interference is due to the electromagnetic fields generated by harmonic currents, which can induce noise in these systems.
High levels of harmonic currents can lead to voltage distortion, which can affect the performance of voltage-sensitive equipment and reduce the overall quality of the electrical power.
The presence of harmonics can reduce the available capacity of an electrical system to carry useful power, as part of the system's capacity is taken up by non-productive harmonic currents.
Why and When to Do a Harmonic Study?
Conducting a harmonic study is essential for identifying, analyzing, and mitigating the effects of harmonic distortion in electrical systems. Here’s why and when it’s particularly important to perform a harmonic study:
Why Do a Harmonic Study?
Many regulatory bodies and industry standards, such as IEEE 519 in the United States, set limits on harmonic distortion levels to ensure reliable and safe operation of electrical systems. A harmonic study helps ensure compliance with these standards.
Harmonic distortion can damage sensitive electronic equipment, reduce the lifespan of electrical infrastructure like transformers and motors, and cause nuisance tripping of circuit breakers. A study identifies risks to equipment and suggests mitigation strategies.
Harmonics cause additional losses in electrical systems, reducing overall efficiency. Identifying and mitigating harmonics can lead to energy savings and reduced operational costs.
Poor power quality can lead to malfunctioning or failure of equipment. A harmonic study helps in understanding power quality issues related to harmonics and in taking corrective actions.
Before adding new loads, especially those known to generate harmonics (like VFDs or data centers), a study can predict how these additions will affect the existing system and guide necessary infrastructure adjustments.
When to Do a Harmonic Study?
Before constructing a new facility or undergoing a significant renovation, especially one that will include harmonic-generating equipment.
If you plan to introduce sensitive electronic equipment into your system, a harmonic study can ensure that the power quality will meet the equipment’s requirements.
If unexplained equipment failures, overheating, or operational issues occur, a harmonic study can determine if harmonics are a contributing factor.
When expanding an electrical system or adding significant new loads, especially non-linear loads, to assess the impact on harmonic levels and the existing infrastructure.
To meet regulatory, safety, or quality standards that require documentation of harmonic levels and mitigation practices.
When expanding an electrical system or adding significant new loads, especially non-linear loads, to assess the impact on harmonic levels and the existing infrastructure.
To meet regulatory, safety, or quality standards that require documentation of harmonic levels and mitigation practices.
As part of efforts to reduce energy consumption and improve operational efficiency, particularly in facilities with high energy usage.
As part of ongoing electrical system maintenance, particularly in facilities with a history of harmonic issues or significant changes in load patterns.
Benefits of Testing in the Electrical Industry
How to mitigate harmonics in the system?
Harmonic frequencies can be selectively absorbed using passive harmonic filters. They are typically placed close to the loads that produce harmonics and tuned to the most troublesome harmonics, like the 5th, 7th, 11th, and 13th. These filters have the ability to greatly decrease the system's harmonic distortion.
The active filter neutralizes the harmonic currents by introducing compensatory currents into the electrical grid. In addition to being able to adjust to different load situations, they are also highly successful in handling a broad variety of harmonic difficulties.
By creating phase displacement among the phases of a power system, these transformers can cancel out certain types of harmonics, especially in systems with rectifiers or other significant non-linear loads.
Although not a direct approach to harmonic mitigation, increasing the power factor of the system can result in a reduction of the overall current flow, thereby contributing indirectly to harmonic mitigation. Nevertheless, extreme care should be exercised, as improperly designed capacitors may resonate with harmonic frequencies and aggravate the issue.
By implementing isolation transformers, the propagation of harmonics from the source to the remainder of the power system can be reduced. They are capable of enhancing the security of delicate apparatus.
Harmonics can be more pronounced in systems with significant unbalanced loads. Balancing the load across phases can help in reducing the overall harmonic distortion.
By derating electrical equipment such as transformers and cables, you can compensate for the additional heat and stress caused by harmonics, thus extending their lifespan and reliability.
Altering the electrical network configuration, for instance, by substituting a wye connection with a delta connection, may occasionally be effective in reducing the impact of specific types of harmonics.
Isolating significant harmonic-generating loads on dedicated circuits can help in reducing the impact of harmonics on the entire system.
Implementing a system for regular monitoring of harmonic levels can help in early detection of issues and ensure that mitigation strategies remain effective over time.
Procedure involved in conducting Harmonic Study
Standards
