The influence of reactive power and the harm of harmonics

1) Reactive power will cause the current to increase and the apparent power, thereby increasing the capacity of the electrical equipment of the generator and transformer and the capacity of the conductor.
 

The size and specifications of the starting and control equipment and measuring instruments of power users should also be increased.

(2) Reactive power increases the total current, thus causing losses in equipment and lines, which is obvious.

(3) It increases the voltage drop of the line and transformer, creates an impact reactive power load, and causes drastic voltage fluctuations, seriously reducing the power supply quality.

2. Harm of harmonics

The voltage provided by the ideal public power grid should be a single and fixed frequency and a specified voltage amplitude. The emergence of harmonic current and harmonic voltage is a kind of pollution to the public power grid. It deteriorates the environment where the electrical equipment is located and also affects the surrounding capacity. Before the widespread application of power electronic equipment, people have studied and recognized the harm of harmonics, but at that time, harmonic pollution was still severely punished and did not attract enough attention. In the past three or four decades, the rapid development of various power electronic devices has made the public power grid harmonic pollution more and more serious, and various faults and accidents caused by harmonics have continued to occur. The severity of harmonic hazards has attracted people's high attention. The hazards of harmonics to public power grids and other systems are roughly as follows.

(1) Harmonics cause additional harmonic losses in components of the public power grid, reducing the efficiency of power generation, transmission and power-consuming equipment. When a large amount of third harmonics flows through the neutral line, it can cause the line to overheat or even cause a fire.

(2) Harmonics affect the normal operation of various electrical equipment. In addition to causing additional losses, harmonics also cause mechanical vibration, noise and overvoltage on motors, causing severe overheating of transformer parts. Harmonics cause capacitors, cables and other equipment to overheat, age their insulation, shorten their lifespans, and even damage them.

(3) Harmonics can cause local parallel resonance and series resonance in the public power grid, thereby amplifying the harmonics. This can greatly increase the hazards of (1) and (2) above and even cause serious accidents.

(4) Harmonics can cause malfunction of relay protection and automatic devices, and inaccurate measurement by electrical measuring instruments.

(5) Harmonics can interfere with nearby communication systems. In mild cases, they can generate noise and reduce communication quality. In severe cases, they can cause loss of residence and make the communication system unable to work normally.