What is a three-phase voltage? How to solve the three-phase voltage instability?

September 04, 2022

. What is a three-phase voltage?

The three-phase voltage is the voltage between the phase and the phase. There are various voltage standards in various countries in the world. The three-phase voltage is 220V, the three-phase 380V is one kind, and there are other voltages. In addition, the frequency is also 50HZ and 60HZ. of. At present, China's three-phase voltage standard is 380V, the frequency between each phase is the same, the frequency is 50Hz. Because the star connection is used for residential electricity access, if China says three-phase 380V, it means the line voltage, and its phase voltage is 220V; if it is three-phase 220V, it means the line voltage, and its phase voltage is 127V. Taiwan and other places are such power sources. Japan is a special case of the world. The east and west parts of Japan are different power grids. The phase voltages are 120V/60HZ and 220V/50HZ, respectively. At the same time, they are connected to the triangular connection used by residents. Therefore, the line voltage and phase voltage in Japan are equivalent. of.

The practical application shows that the three-phase power factor can be compensated to above 0.95, and the unbalanced current is adjusted to within 10% of the rated current of the transformer. According to the wangs theorem (Wang's theorem), a capacitor that is connected across phases can transfer active current between phases. Adjusting the unbalanced current reactive power compensation device is designed by using the wangs theorem. Appropriately connecting different numbers of capacitors between each phase and phase and between each phase and the neutral line can not only make the phases get good. Compensation, and the unbalanced active current can be adjusted. The commutation switch automatically selects the power supply phase through intelligent logic to automatically adjust the imbalance of the three-phase load. Reduce the loss of electrical energy during transmission, maximize the utilization of electrical energy and enhance the reliability of power supply

Solution to the three-phase voltage imbalance caused by asymmetric load 1. Distribute the asymmetric load to different power supply points to reduce the problem that the imbalance is seriously exceeded due to centralized connection. 2. Use the cross-change equal method to distribute the asymmetric load to each phase reasonably and try to balance it. 3. Increase the short-circuit capacity of the load access point, such as changing the network or increasing the supply voltage level to improve the system's ability to withstand unbalanced loads. 4. Install a balancing device. Briefly list the above technical measures to solve the three-phase voltage or current imbalance on the grid and power quality hazards.

Which kind of measures should be taken is more reasonable and effective, and it must be determined according to the actual situation and after technical and economic comparison. In the low-voltage three-phase four-wire urban residents and rural power supply systems: because the electricity users are mostly single-phase load or single-phase and three-phase load mixed, and the load size is different and the power consumption time is different. Therefore, the unbalanced current between the three phases in the power grid exists objectively, and this power imbalance is irregular and cannot be predicted in advance. This results in a long-term imbalance in the three-phase load of the low-voltage power supply system. For three-phase unbalanced currents, the power sector has few effective solutions in addition to distributing the load as reasonably as possible. The unbalanced current in the power grid will increase the copper loss of the line and the transformer, and will increase the iron loss of the transformer. Lowering the output of the transformer may even affect the safe operation of the transformer, which will eventually cause an imbalance of the three-phase voltage. Adjusting the unbalanced current reactive power compensation device-automatically adjusting the capacitor bank effectively solves this problem. The device has the function of adjusting the unbalanced active current while compensating the system for reactive power. The theoretical result can compensate the three-phase power factor to 1, and the three-phase current is adjusted to balance.

The practical application shows that the three-phase power factor can be compensated to above 0.95, and the unbalanced current is adjusted to within 10% of the rated current of the transformer. According to the wangs theorem (Wang's theorem), a capacitor that is connected across phases can transfer active current between phases. Adjusting the unbalanced current reactive power compensation device is designed by using the wangs theorem. Appropriately connecting different numbers of capacitors between each phase and phase and between each phase and the neutral line can not only make the phases get good. Compensation, and the unbalanced active current can be adjusted. The commutation switch automatically selects the power supply phase through intelligent logic to automatically adjust the imbalance of the three-phase load. Reduce the loss of electrical energy during transmission, maximize the utilization of electrical energy and enhance the reliability of power supply.

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