三绕组变压器低压侧直供负荷对中压配电网技术经济性的影响

现有高、中压网络规模估算模型通常假设高压变电站主变为双绕组变压器,但220 kV变电站主变多为三绕组变压器,其低压侧直供负荷会影响110 kV变电站的布局和规模,为此建立了计及三绕组变压器低压侧直供负荷影响的高、中压网络规模估算模型。在此基础上,针对城市新建区和城市改造区分别分析了220/110/10(20)kV三绕组变压器低压侧直供负荷对220/110/10、220/110/20、220/20 kV方案技术经济性的影响。分析结果表明,对于城市改造区,不考虑主变低压侧负荷直供情况下得到的发展20 kV技术经济性最优结论,在主变低压侧有直供负荷时可能不再成立。

Influences of Direct-Fed Load at Low Voltage Side of Three-Winding Transformer on Techno-Economical Performance of Medium Voltage Distribution Network

In existing models to estimate the scale of high-and medium-voltage power network,it s normally assumed that the main transformers of HV substations are two-winding transformers,however in 220 kV substations their main transformers are mostly three-winding transformers,so the direct-fed loads at their low-voltage side will influence on both layouts and scales of 110 kV substations.For this reason,a model to estimate the scale of high-and medium voltage network,in which the influence of direct-fed load at low-voltage side of three-winding transformer is taken into account,is built.On this basis,the influences of direct-fed loads at low voltage side of 220/110/10 kV and 220/110/20 kV three-winding transformers on the techno-economical performances of 220/110/10 kV,220/110/20 kV and 220/20 kV schemes for newly built urban areas and those for renewal urban areas are analyzed respectively.Analysis results show that for renewal urban areas,the conclusion that adopting voltage grade 20 kV for low-voltage network can bring optimal techno-economical performance,which is obtained under the condition that the direct-fed load of low-voltage side of three-winding transformer is not taken into account,could be no more tenable.