Reactive power compensation can improve voltage quality and improve power factor, and is one of the energy-saving measures adopted by the power grid. The reactive power compensation method commonly used in the distribution network is: in the part of the system, in the power distribution station, the reactive power compensation device is installed in each user; the parallel capacitor unit is dispersedly installed in the high and low voltage distribution lines; Parallel capacitors are installed between the low-voltage side and the workshop power distribution panel, and parallel capacitors are installed near a single motor for local or distributed local compensation.
1. Local compensation
For large motors or high-power electrical equipment, local compensation devices should be installed. Local compensation is the most economical, simplest and most effective way to compensate. In the local compensation method, the capacitor is directly connected to the electric equipment, and only the series fuse is protected in the middle. When the electric equipment is put into the capacitor, the capacitor is put together, and the piece is cut off when the cutting is performed, thereby realizing the most convenient reactive power automatic compensation. The coil of the electrical device at the time of cutting is the discharge coil of the capacitor.
2, dispersion compensation
When each user terminal is far away from the main transformer, it is preferable to install a dispersion compensation device at the end of the power supply, and the low-voltage compensation of the user end can greatly reduce the line loss, and at the same time, the effect of raising the terminal voltage can be taken into consideration.
3. Centralized compensation
The reactive power compensation in the substation is mainly to compensate the main transformer's demand for reactive power, and to determine the reactive power compensation capacity by considering the reactive power flow in the voltage supply area and the reactive power compensation level of the distribution line and the user. The 35KV substation is generally determined by 10%-15% of the main transformer capacity; the 110KV substation can be determined by 15%-20%.
4, the choice of volume adjustment
(1) Long-term changing load
For the case where the initial load of the station is small and the load is gradually increased, the unloaded adjustable capacitor bank is assembled. Adjustable capacitive capacitors are available for outdoor installations; adjustable cabinet capacitors are available for indoor installation. The basic principle is that the capacitors are divided into two groups in a binary manner, and the switching combination can be selected by the tap changer or the isolating switch, so that the third gear capacity can be adjusted. As the load changes, the switching combination can be changed to meet the reactive balance of a certain period of time after manual power-off. In this case, a reactive power automatic adjustment device can be installed, which can meet the requirements of unattended integrated automation.
(3) When the load changes frequently in a short period of time
In this case, a transient reactive power compensation device that can be quickly tracked should be installed. Since the capacitor must ensure that there is no residual charge before the capacitor is switched, the capacitor discharge takes several seconds even if it passes through the discharge coil. Therefore, the high-voltage transient reactive power compensation device (also called SVC) is generally fixed to compensate the maximum capacity. The capacitor is connected in parallel with a set of reactors with adjustable capacity to achieve the reactive transient balance by quickly adjusting the output of the reactor to be reactive. The adjustment technology of the reactor mainly includes two methods: the thyristor control hollow shunt reactor and the DC bias magnetic sensation, among which the former is superior, but the price is high.
Reactive power compensation optimization
1 Strengthening the meaning of reactive power compensation for medium and low voltage distribution networks in rural power
There is a large amount of reactive power in the power system, which causes the power system to transmit a large amount of reactive power while transmitting active power. Moreover, due to insufficient configuration of the reactive power compensation device, the voltage of the agricultural network distribution network is reduced, and the line loss is increased. Problems such as insufficient conveying capacity are more prominent. The distribution network is the end of the power grid. The line loss and voltage drop generated by the same voltage of the low voltage transmission are higher than that of the high voltage network. Although the transformation of the rural power grid has significantly improved the distribution network of the rural power grid, the reactive power compensation and reconstruction are not reasonable. In particular, with the increase of state policy support to the rural areas, the rural economic development has shown a good and stable development trend. The rural power consumption and non-linear load users have grown rapidly, and the distribution network with insufficient reactive power allocation has increased. burden. Therefore, strengthening the optimal configuration of reactive power compensation for medium and low voltage distribution networks and maintaining reactive power balance plays an important role and significance for ensuring power quality, reducing power grid losses, and improving grid transmission capacity and equipment utilization, in line with State Grid Corporation. The requirements of the 11th Five-Year Plan for the Reactive Development of Rural Power Network.
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