配电网变电站并列运行三绕组变压器无功补偿的经济分析

Economic Analysis on Reactive Power Compensation for Parallel-Operated Three-Winding Transformers in Distribution Network

配电网变电站三绕组变压器的无功补偿大多数是在低压侧安装并联运行的单组或多组电容器,传统上电容器投入与否或投入几组是根据变压器电源侧的功率因数大小来控制。这种控制方法的缺点是:仅考虑功率因数提高减少了变压器损耗的因素,而忽视了投入电容器介质损耗增大的因素。讨论了配电网两台三绕组变压器中压侧分列低压侧并列运行时,并联无功补偿电容器的经济运行;根据变压器损耗与电容器介质损耗之和最小的原则分析计算投切电容器组的临界负载,发现在某些条件下提高功率因数不仅不节电反而浪费电量;并在此基础上提出判断电容器经济运行的方法:最后举例说明了经济运行的节电效果。

The reactive power compensation of three-winding transformer in distribution substation is mostly realized by shunt single capacitor bank or multi capacitor banks installed at the transformer＇s low voltage side, traditionally it is depended by the value of power factor at the mains side that whether the capacitor banks are put into operation or not and how much capacitor banks should be switched on. The defect of such compensation method lies in that only the transformer loss decrement by improving power factor is considered, but the dielectric loss increment of capacitors put into operation is neglected. Here, the economic operation of shunt compensating capacitors is researched when the low voltage sides of two three-winding transformer in distribution network are operated in parallel and at the same time the medium voltage sides of the two transformers are separately operated. According to the principle that the sum of transformer loss and dielectric loss of capacitors is minimum the critical load, by which the capacitor bank is switched, is calculated and analyzed, the result is that under certain conditions the sum of transformer loss and dielectric loss of capacitors cannot be reduced, but increased. On this basis a method to judge the economic operation of capacitor banks is proposed, and the result of saving electric energy by economic operation is illustrated.