How are harmonics generated and their hazards in industrial and mining enterprises? How to eliminate

In the power system, the distortion rate of the generator outlet voltage is required to be less than 5, so the power supply of the power system can be considered as a sinusoidal voltage waveform. The generation of harmonics in the power system is mainly caused by the existence of a large number of nonlinear loads. A nonlinear load is one in which the current flowing through the load is not proportional to the voltage applied to the load.

Thirty years ago, nonlinear loads were mainly power transformers. In the over-excitation state, the power transformer will produce a large number of 3rd harmonic currents due to the saturation of the core. In the past 30 years, with the development of the power electronics industry, power electronic equipment has been distributed in the details of the entire power grid.

There are mainly computers, televisions, air conditioners, these electrical equipment using switching power supplies, although the capacity of these devices is small, but the number is huge and widely distributed, has become the main source of pollution of harmonic current in the power system. The development of electric railways has made the harmonics of electrified railways increasingly serious. The harmonic currents of intermediate frequency furnaces and electric arc furnaces used in industrial smelting are also quite serious.

The main hazards of harmonics are:1Harmonics cause additional losses in public network components, reducing the efficiency of power generation, transmission and electrical equipment.

2 Harmonics from skin effects can overheat the cable and accelerate insulation aging.

3. Harmonics will produce local string and parallel resonance, which endangers the safety of power equipment, especially the safety of power capacitors.

4. A large amount of 3 times harmonic current will make the center line current too large, and even burn the center line, causing a fire.

5. Harmonics will make the relay protection device malfunction, so that the measurement of electrical instruments is inaccurate.

6 Harmonics can interfere with nearby communication signals.

How to solve the harm caused by harmonics is a relatively large topic. At present, it is mainly grasped from two aspects, one is to try not to produce it, which is mainly in the article on electrical equipment. One is local filtering, which refers to the installation of power filters near the harmonic source to make the harmonics filter out locally without harming the public network.

Do you want to eliminate higher or lower harmonics.

The elimination of low times + the improvement of the power factor is generally more than 1,000 per kilowatt, the result is to improve the power factor, contribute to the power grid free of charge, and reduce the power supply bureau because of your serious waveform distortion, low power factor, and the fine of the unit.

The treatment of high-order harmonics can achieve the purpose of saving electricity, generally about 100 yuan per kilowatt, and the cost will be recovered in 2 years. xian_

1. The main reason is that there are various nonlinear components in the system, especially large-scale thyristor converter equipment and large-scale electric arc furnaces, and the high-order harmonics generated by them are the most prominent.

2. The harm of harmonics can increase the iron loss of motors and transformers, and even overheat and shorten the service life. It will also cause the rotor of the motor to vibrate, which seriously affects the machining quality. For capacitors, the overload phenomenon of the deficit ridge can occur and cause damage.

In addition, the energy consumption of the power line can be increased, the inductive electric energy meter of the billing is not accurate, the relay protection and automatic device of the system malfunction, the voltage resonance of the system can occur, and the signal interference can be generated to the nearby communication equipment and lines.

3. The measures to suppress harmonics are:

The three-phase rectifier transformer adopts the wiring of Y, D or D, Y to eliminate the rectifier multiple higher harmonic of 3, which is one of the most basic measures.

Increase the number of phases on the secondary side of the rectifier transformer.

Install a shunt filter.

Static reactive power compensation device (SVC) is installed

Limit the capacity of the converter and alternating voltage regulators connected to the system and increase the power supply voltage for large-capacity nonlinear equipment.

The components in the power grid produce additional harmonic losses, reduce the efficiency of power generation, transmission and electrical equipment, and a large number of 3rd harmonic flows through the neutral line will overheat the line and even cause fire.

The power supply of the inverter system is independent of the power supply of other equipment, or an isolation transformer is installed on the input side of the inverter and other electrical equipment.

Or put the inverter into the iron box, and the iron box shell is grounded. At the same time, the output power supply of the inverter should be as far away as possible from the control cable laying, and it must be close to the laying as far as possible to cross at an orthogonal angle, and the length of the parallel section must be shortened as much as possible when the pure setting of the inverter is returned, and the output cable should be through the steel pipe and the steel pipe should be electrically connected and reliably grounded.

The causes and hazards of harmonics are introduced as follows

The fundamental cause of harmonic generation is the waveform distortion caused by the nonlinear nature of some equipment and loads in the power grid, that is, the applied voltage is not linear (proportional) to the generated current.

Hazards: Due to the high frequency of harmonics, the skin effect of the wire is aggravated, so the copper loss increases dramatically. At the same time, the transformer core cannot adapt to the rapidly changing magnetic flux, resulting in a sharp increase in iron loss.

Suppression: The generation of power harmonics is often greatly related to the unreasonable electrical design, so it is necessary to fundamentally solve the problem of power harmonics and first optimize the electrical design to avoid the occurrence of power harmonics. In this regard, it is necessary to take technical measures to avoid harmonics when conducting electrical design, such as:

Increase the number of rectifier pulsations. Rectifiers are the main harmonics in the power supply network.

PWM technology is pulse-width modulation technology, and the principle of using this technology to reduce harmonics is:

1) PWM can increase the harmonic spectrum and reduce the harmonic amount, which can make the input of the converter a sine wave;

2) The power factor correction (PFC) is added behind the controllable rectification, which can also achieve the purpose of controlling the input current as sinusoidal, and the PFC can be phase corrected, so that from the grid side, the load can be equivalent to a linear load.

Summary. Hello, I am glad to answer for you, the main reasons for harmonics are: due to the sinusoidal voltage pressurized by the nonlinear load, the fundamental current is distorted to produce harmonics. The main nonlinear loads are UPS, switching power supply, rectifier, inverter, inverter, etc.

Hello answer, I am happy to answer for you, the main reasons for harmonic generation are: due to the sinusoidal voltage pressurized by the nonlinear load, the fundamental electric Qingqin flow distortion family only produces harmonics. The main nonlinear loads are UPS, switching power supply, rectifier, inverter, inverter, etc.

The hazards of harmonics can be eliminated by:1Reactors and filters are installed on the power lines to reduce the impact on power equipment by absorbing and filtering harmonics.

2.The nonlinear load is reasonably configured and managed to reduce the generation of harmonic sources. 3.

Condition monitoring and diagnosis of power equipment, timely detection and treatment of harmonic problems. 4.Strengthen the stability and reliability management of the power system, prevent and reduce faults and accidents caused by harmonics.

5.Reasonable planning and wiring of communication lines to avoid harmonic interference to communication equipment. 6.

Carry out reasonable design and transformation of industrial equipment to reduce the impact of harmonics on production. 7.Strengthen the publicity and education of the public, and improve the public's awareness of environmental protection and harmonic governance.

I hope the above information is helpful to you, and if you have any other questions, welcome to let me know.

Summary. Dear, I'm glad to answer for you;

Answer: Harmonics refer to the sine wave component of an electrical quantity. Its frequency is an integer multiple of the fundamental frequency, and harmonics of different frequencies will have different effects on different electrical equipment.

Suppression methods: 1. Improve the power supply system; 2. Reduce the harmonic content of the harmonic source; 3. Absorb harmonic current at the harmonic source.

Harmonic generation: In an ideal clean power supply system, both current and voltage are sine waves. In a simple circuit with only linear elements, the current flowing through is proportional to the applied voltage, and the current flowing through is a sine wave.

In the actual power supply system, due to the existence of nonlinear loads, when the current flows through the load that is not linear to the applied voltage, a non-sinusoidal current is formed. Any periodic waveform can be broken down into a fundamental sine wave plus many harmonic frequencies. The harmonic frequency is an integer multiple of the fundamental frequency.

How to eliminate the causes and hazards of harmonics?

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Dear, I'm glad to answer for you; How to eliminate the causes and hazards of harmonics? Answer: Harmonics refer to the sine wave component of an electrical quantity.

Its frequency is an integer multiple of the fundamental frequency, and harmonics of different frequencies will have different effects on different electrical equipment. Suppression methods: 1. Improve the power supply system; 2. Reduce the harmonic content of the harmonic source; 3. Absorb harmonic current at the harmonic source.

Harmonic generation: In an ideal clean power supply system, both current and voltage are sine waves. In a simple circuit with only linear elements, the current flowing through is proportional to the applied voltage, and the current flowing through is a sine wave.

In the actual power supply system, due to the existence of nonlinear loads, when the current flows through the load that is not linear to the applied voltage, a non-sinusoidal current is formed. Any periodic waveform can be decomposed into a fundamental sine wave plus many harmonic frequencies of the sine wave. The harmonic frequency is a Patrick integer multiple of the fundamental frequency.

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Harmonic refers to the amount of electricity contained in the current whose frequency is an integer multiple of the fundamental wave, and generally refers to the amount of electricity generated by the Fourier series decomposition of the periodic non-sinusoidal charge, and the rest of the current greater than the fundamental frequency.

At present, the electrical equipment is complex and complex, and the nonlinearity of the load is becoming more and more common, which has caused a great threat to the safe and normal operation of the power system and equipment. Among them, such as air conditioners, Zenshou pumps, fans, local elevators, computer room network equipment, office equipment, UPS, lighting control systems, fire protection systems, monitoring systems and other power electronic equipment.

Hazards of harmonics:

The generation of harmonics will reduce the capacity of the system, accelerate the aging speed of the equipment, and even damage the equipment, endanger the safety and stability of the production of raw feet, waste of electric energy, etc.;

For large-scale industrial production, the method of harmonic control is nothing more than the envy of the two lings: active filtering and passive filtering. The selection of these two filtering methods is mainly based on the specific working conditions and treatment objectives.

Each method has its own advantages and characteristics. Due to the specific situation of each project, it is recommended that enterprises can choose several harmonic control manufacturers, compare the treatment plans of each one, and choose the solutions and products that suit them after comprehensive consideration.

Harmonic current is the root of all harmonic problems, and the harmonic mode potato wave voltage is also caused by the positive harmonic current of the hand. Therefore, when studying the hazards caused by harmonics, it mainly refers to the hazards of harmonic currents.

causing the cable to overheat;

causing the transformer to overheat;

Damage to variable reactive power compensation device;

special hazards of the third harmonic;

adverse effects on other electronic devices; Dan search.

resulting in accidental tripping;

Resulting in additional energy loss.