Voltage fluctuations and flicker hazards are manifested in: ① lighting flicker, causing visual discomfort and fatigue, affecting efficiency; ② TV screen brightness changes, vertical and horizontal amplitude shaking; ③ motor speed is not uniform, affecting the quality of the product; ④ so that the electronic instruments, electronic computers, automated control equipment, etc., work properly; ⑤ impact on the voltage fluctuations in the more sensitive process or test results. Voltage fluctuation value for the voltage amplitude modulation wave in the adjacent two extreme value voltage Um.: and U,. Root-mean-square difference △ U, often expressed as a percentage of its rated voltage UN its relative percent
China's national standard GB12326 a 90 ((power quality voltage fluctuations and flicker allowable" stipulates that the voltage fluctuations in the public *** power supply point of the permissible value, as shown in Table 1. Research has proved that the human eye on the frequency of about 10H: the decay 1 voltage fluctuations allowable voltage fluctuations are most sensitive, and for this reason generally use the equivalent 10H: fluctuations △ Vl. as a measure of flicker indicators. In addition, "flicker" is the lighting brightness changes in the human stimulus, the discomfort of this stimulus should be measured by the average value of a period of time, therefore, where △ V month for the voltage amplitude modulation wave in the frequency of f sinusoidal components of a minute root-mean-square average, expressed as a percentage of the rated voltage; aj for the flickering visualization coefficients. China's current national standards recommended △Vl. allowable values are shown in Table 2. Wrap 2 △ V. Allowable value of high-power impact loads, such as large motors with frequent starting and stopping or arc furnace melting period and other voltage fluctuations occurring more than the permissible value of the occurrence of flicker disturbances, measures must be taken to address.