To increase the power factor of the power supply and distribution system, we can first make full use of the capacity of the power supply equipment, improve the utilization rate of power generation and transformation equipment, and secondly, reduce the power loss and voltage loss of power supply lines and electrical equipment, thus saving energy and stabilizing transmission and distribution. The role of electric voltage.
The main means of reactive power compensation is the use of synchronous compensators or power capacitors. Compared with the synchronous compensator, the parallel capacitor has the advantages of no rotation, simple installation, convenient operation and maintenance, low active loss, flexible assembly, and easy expansion. Therefore, it is most commonly used in power supply and distribution systems.
Because the reactive power load and line resistance of different places in the distribution network are different, the effect produced by installing capacitors at different locations is also different, even if the effect of the device capacitor at the same location is reduced with the increase of the compensation capacity. In the power supply and distribution system, how to obtain the best economic effect of reactive power compensation is a problem that should be studied when configuring a capacitor.
1 Optimal configuration of capacitors in radial distribution networks 10 kV radial distribution networks with n distribution lines are shown in Fig. 1. Before compensation, the load of each distribution line is P, Q, P, Q:,..., P, Q. The equivalent resistance of each distribution line is R, R. ...R. It is now necessary to place a capacitor with a total capacity of ΣQ on each distribution line to achieve maximum loss reduction.
When the system active power flows ΣP, P are constant, the active power loss of each wiring and system only changes with the change of reactive power flow. Therefore, as long as the required configuration of the capacitor of ΣQ capacity is reasonably allocated to n distribution lines, the active power loss of the entire distribution system can be minimized, even if the active loss of the system after compensation is Σap; the first derivative of Q can be obtained. Maximum loss reduction effect.
In summary, the optimal configuration of the capacitor in an radiating power distribution system is such that the entire distribution system is equal to the equivalent reactive power economic equivalent after compensation.
If a negative value occurs in calculating the Q of some lines by the above method, it indicates that the original economical equivalent of reactive power of these lines is less than the economic equivalent of the reactive power compensated by the distribution network, and no compensation capacitor is required to be installed.
2 The example proves that 3 500 kvar capacitors are to be installed on the radial distribution network to try to find the optimal capacitor capacity for each distribution line.
After checking the reactive economic equivalent of each distribution line and the entire network after compensation, the reactive economic equivalent of each distribution line and the whole network is 20.52×10-kW/kvar.
From the results of this example, it is further shown that the optimal configuration of the capacitors in the radial grid is that the distribution lines reach the same reactive economic equivalent after compensation.
3 Optimal configuration of the capacitor in the distribution line When it is known that a certain distribution line should be equipped with a capacitor capacity, there is also a problem that an optimal configuration of a capacitor exists between the branch lines of the distribution line.
The connection point between the trunk line and the branch line of the distribution line is called a node. If each node is considered as a bus, the above principles apply to each node of the distribution line.
Calculations should be made as follows:
(1) First, calculate the reactive power flow of each segment of the trunk line, 0l2, Q23...
(2) Calculate the equivalent resistance of each node and calculate them one by one in the order from the last node forward;
(3) The capacity of the capacitors to be distributed in each branch is calculated one by one in the order from the first branch. If the zero value of a branch line is negative in the calculation, it means that the branch line does not need to install a capacitor, then Q=0 is taken from this point, but the next branch line is calculated again.
In short, no matter whether it is the distribution lines of the radial distribution network or the distribution lines, the best configuration condition for reactive power compensation is to make the reactive economic equivalent of each distribution line (or branch) tend to Equal, rather than having each line compensated to the same power factor value.
However, the reactive power compensation economic equivalent refers to the ratio of the active power loss value to the reactive power reduction value that is reduced due to the reduction of the reactive power, that is, the loss value kW of the active power reduction when the reactive power delivered is reduced by 1 kvar. In the implementation of power grid reactive power compensation, the compensated reactive economic equivalent will decrease with the increase of the compensation capacity, so that the economic effects of the power factor will be affected as a result of the active power loss of the line:
When Q>ΔQ, c is 2CP; When QΔp, c is CP, that is, C 1/2C, that is, when the compensation capacity is larger, its effect on reducing active power loss will be smaller, and the compensation device The economic effect of increasing the power factor is reduced. Therefore, in order to avoid over-compensation causing reactive power reversal, the compensation capacity should be less than the reactive power of this section as an additional condition, that is, Q
4 Conclusion As the reactive power load and line resistance of different locations in the distribution network are different, the effect that the device can produce at different locations is also different, even if the effect of the device capacitor at the same location is reduced with the increase of the compensation capacity. The analysis of this research shows that the optimal configuration condition for the compensation of no-work compensation between the distribution lines of the radial distribution network and the distribution lines is to make the reactive economy of each distribution line (or branch). The equivalents tend to be equal.
The main means of reactive power compensation is the use of synchronous compensators or power capacitors. Compared with the synchronous compensator, the parallel capacitor has the advantages of no rotation, simple installation, convenient operation and maintenance, low active loss, flexible assembly, and easy expansion. Therefore, it is most commonly used in power supply and distribution systems.
Because the reactive power load and line resistance of different places in the distribution network are different, the effect produced by installing capacitors at different locations is also different, even if the effect of the device capacitor at the same location is reduced with the increase of the compensation capacity. In the power supply and distribution system, how to obtain the best economic effect of reactive power compensation is a problem that should be studied when configuring a capacitor.
1 Optimal configuration of capacitors in radial distribution networks 10 kV radial distribution networks with n distribution lines are shown in Fig. 1. Before compensation, the load of each distribution line is P, Q, P, Q:,..., P, Q. The equivalent resistance of each distribution line is R, R. ...R. It is now necessary to place a capacitor with a total capacity of ΣQ on each distribution line to achieve maximum loss reduction.
When the system active power flows ΣP, P are constant, the active power loss of each wiring and system only changes with the change of reactive power flow. Therefore, as long as the required configuration of the capacitor of ΣQ capacity is reasonably allocated to n distribution lines, the active power loss of the entire distribution system can be minimized, even if the active loss of the system after compensation is Σap; the first derivative of Q can be obtained. Maximum loss reduction effect.
In summary, the optimal configuration of the capacitor in an radiating power distribution system is such that the entire distribution system is equal to the equivalent reactive power economic equivalent after compensation.
If a negative value occurs in calculating the Q of some lines by the above method, it indicates that the original economical equivalent of reactive power of these lines is less than the economic equivalent of the reactive power compensated by the distribution network, and no compensation capacitor is required to be installed.
2 The example proves that 3 500 kvar capacitors are to be installed on the radial distribution network to try to find the optimal capacitor capacity for each distribution line.
After checking the reactive economic equivalent of each distribution line and the entire network after compensation, the reactive economic equivalent of each distribution line and the whole network is 20.52×10-kW/kvar.
From the results of this example, it is further shown that the optimal configuration of the capacitors in the radial grid is that the distribution lines reach the same reactive economic equivalent after compensation.
3 Optimal configuration of the capacitor in the distribution line When it is known that a certain distribution line should be equipped with a capacitor capacity, there is also a problem that an optimal configuration of a capacitor exists between the branch lines of the distribution line.
The connection point between the trunk line and the branch line of the distribution line is called a node. If each node is considered as a bus, the above principles apply to each node of the distribution line.
Calculations should be made as follows:
(1) First, calculate the reactive power flow of each segment of the trunk line, 0l2, Q23...
(2) Calculate the equivalent resistance of each node and calculate them one by one in the order from the last node forward;
(3) The capacity of the capacitors to be distributed in each branch is calculated one by one in the order from the first branch. If the zero value of a branch line is negative in the calculation, it means that the branch line does not need to install a capacitor, then Q=0 is taken from this point, but the next branch line is calculated again.
In short, no matter whether it is the distribution lines of the radial distribution network or the distribution lines, the best configuration condition for reactive power compensation is to make the reactive economic equivalent of each distribution line (or branch) tend to Equal, rather than having each line compensated to the same power factor value.
However, the reactive power compensation economic equivalent refers to the ratio of the active power loss value to the reactive power reduction value that is reduced due to the reduction of the reactive power, that is, the loss value kW of the active power reduction when the reactive power delivered is reduced by 1 kvar. In the implementation of power grid reactive power compensation, the compensated reactive economic equivalent will decrease with the increase of the compensation capacity, so that the economic effects of the power factor will be affected as a result of the active power loss of the line:
When Q>ΔQ, c is 2CP; When QΔp, c is CP, that is, C 1/2C, that is, when the compensation capacity is larger, its effect on reducing active power loss will be smaller, and the compensation device The economic effect of increasing the power factor is reduced. Therefore, in order to avoid over-compensation causing reactive power reversal, the compensation capacity should be less than the reactive power of this section as an additional condition, that is, Q
4 Conclusion As the reactive power load and line resistance of different locations in the distribution network are different, the effect that the device can produce at different locations is also different, even if the effect of the device capacitor at the same location is reduced with the increase of the compensation capacity. The analysis of this research shows that the optimal configuration condition for the compensation of no-work compensation between the distribution lines of the radial distribution network and the distribution lines is to make the reactive economy of each distribution line (or branch). The equivalents tend to be equal.
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