Voltage fluctuations and voltage flicker

Update date:2018-04-14 Source:MAXGE

Voltage fluctuations and voltage flicker

Fluctuations and flicker hazards

Flashing lights, causing people's visual discomfort and fatigue, affecting work efficiency; TV screen brightness changes, vertical and horizontal amplitude shaking;

Uneven motor speed, affect product quality;

Makes electronic instruments, electronic computers, automatic control equipment, etc. not function properly; affects processes or test results that are sensitive to voltage fluctuations.

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The relationship between fluctuations and voltage flicker

Flicker is a special case of voltage fluctuations, which mainly reflects the annoying effects of frequent visual fluctuations in the voltage caused by lighting. The generalized flicker includes all the harmful effects of voltage fluctuations, but it cannot replace the flicker with voltage fluctuations because flicker is a subjective visual sensation of human control fluctuations.

When there are impact power loads (such as rolling mills, electric arc furnaces) in the power system, the voltage drop in the power network will change accordingly, resulting in voltage fluctuations. Voltage fluctuations make electricity users unable to work properly. The most affected in people's lives is the flicker of incandescent lamps. The voltage fluctuation value in the frequency range of 5-12Hz, even if only 1% of the rated voltage, which causes the flickering of the incandescent lamp lighting, is enough to make people feel uncomfortable, so select the incandescent lamp operating conditions as the judgment of voltage fluctuations Value, the subjective feeling of people's flashing light caused by voltage change is called "flicker"

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Voltage flicker is different from common voltage fluctuations.

Voltage flicker refers to a rapid rise and fall in the voltage shape, and the fluctuate refers to that the effective value of the voltage changes rapidly or continuously at a frequency lower than the power frequency; the flicker is characterized by ultra-high voltage, transient state, and high frequency. If intuitively understood from the waveform, the voltage fluctuations can cause waveform distortion, asymmetry, adjacent peak changes, etc., but the waveform curve is smooth and continuous, while the flash change is mainly caused by the waveform's glitches and breaks.

Voltage fluctuations and flicker measures

The commonly used technical measures are:

Improve the operation and process: technical measures such as step-down starting of the motor, automatic adjustment of the electrode movement of the electric arc furnace, and crushing of large waste iron and steel blocks in the charge;

Improve the power supply capacity; set up a dedicated line to connect large-volume impact load users to a higher voltage power supply system;

Installation of compensators: The use of fast-response static var compensators or static var generators for real-time dynamic compensation of load fluctuations is the most commonly used technical measure.

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Monitoring of power quality such as voltage fluctuations and flicker

In the early days of power system development, the composition of the power load was relatively simple, consisting mainly of linear loads such as synchronous motors, asynchronous motors, and various lighting devices. With the development of power electronics technology, nonlinear power electronic devices and devices have been widely used in modern industry. The operation of these devices makes the distortion of voltage and current waveforms in the power grid more and more serious, and the level of harmonics continues to rise. In addition, impact and fluctuating loads, such as electric arc furnaces, large-scale rolling mills, etc., not only generate a large number of higher-order harmonics during operation, but also generate power quality problems such as voltage fluctuations, flicker, and three-phase imbalance.

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