Analysis of the influence of harmonics in electrical power

Sources of harmonics

There are many reasons for the generation of harmonics, so there are relatively many sources, and the types of equipment involved also show certain diversified characteristics. Among them, the main sources of harmonics mainly include transformer groups in the power grid, industrial electric arc furnaces, larger single-phase power electronic devices, and a wide range of rectifier equipment and AC voltage regulating equipment.

Harmful analysis of harmonics

The existence of harmonics in the power system is equivalent to the pollution source of the power system, and the pollution object is mainly the electromagnetic environment in the power system. As an important environmental component of the power system, the electromagnetic environment will show different hazards under the influence of different degrees of harmonics. However, this least harmfulness will also reduce the working efficiency of electrical equipment, and the most serious consequences may lead to persecution of the stable and safe operation of the power system and damage to the electrical equipment. The harm to harmonic generation specifically includes the following aspects:

(1) The electrical equipment is abnormally heating up under the action of harmonics, and the additional loss is too large. Although there is a large gap between the amount of harmonic current and the fundamental current, the presence of harmonics will aggravate the skin effect of the device, and the effective resistance will increase in the process of sensing the skin effect. For some special equipment, large eddy current loss and hysteresis loss will also occur, such as electrical equipment with iron cores. When the waveform is distorted to a certain extent, a large amplitude peak wave will increase the intensity of the partial discharge. Under such high consumption conditions, it is easy to reduce the service life of electrical equipment.

(2) The motor may cause mechanical vibration. Under the influence of harmonic currents, the rotating magnetic field of the motor will produce pulsating torque that can cause the motor to vibrate. Under the influence of the natural frequency of the motor, this kind of vibration can easily cause a more harmful mechanical vibration, thereby endangering the quality of electrical equipment and even threatening people’s lives.

(3) Interference to computer equipment and other automatic control devices. Under normal circumstances, automatic control equipment and other related automatic control systems are designed based on normal current and loaded voltage. When harmonics are generated, the automatic control system does not take this influencing factor into account, making it easy Interference affects the performance of its control function. When the pollution degree of the harmonics is large, it is also possible to change the operating procedures of the automatic control system, causing it to produce wrong guidance. This kind of influence will seriously affect the actual production and operation, and even cause irreversible safety accidents.