Quantitative Analysis Of The Influence Of Three-phase Unbalance On The Additional Loss Consumption In 10kV Distribution Network

Electric power industry is the main industry of energy consumption in China.With the exhaustion of fossil energy and the deterioration of human environment,it is of great significance to carry out effective loss reduction of power system.With the large number of power electronic devices and inverters connected in low-voltage distribution network and the sharp increase of load types and social power consumption,the proportion of single-phase load,non-linear load and impact load on distribution network side has increased significantly,so the power quality problems,especially the three-phase unbalance problem in distribution network are becoming more and more serious.Therefore,the analysis and research of the theoretical line loss caused by the three-phase unbalance factor is essential for quantifying the effects of three-phase unbalance and effectively implementing the loss reduction.According the main research contents of this paper are as follows:Firstly,based on the analysis of the factors affecting the loss of the distribution network,this paper puts forward the index of the influence of the system on the increase of the loss of the distribution network under static factors and dynamic factors,and summarizes the current commonly used loss calculation methods of the distribution network,and points out that the traditional loss calculation of the distribution network does not consider the influence of three-phase unbalanced factors.Then,this article through to the generation of unbalanced three-phase and concepts,and analyses the influence of unbalanced three-phase power loss,the influence mechanism,and by introducing the concept of three-phase imbalance degree,comprehensive consideration in three-phase unbalanced amplitude and phase Angle,puts forward the main distribution equipment additional loss caused by three-phase imbalance model.Based on the operation data of a practical pilot project,the relationship between each three-phase unbalance and 10 kV distribution circuit,10/0.4kV distribution transformer and 10 kV distribution circuit is quantitatively analyzed,and the relationship between each three-phase unbalance and the additional loss of 10 kV distribution network is quantitatively analyzed by using the equivalent resistance method.In PSCAD simulation software as a platform,under the condition of ensure the completely same device data,set up a balanced and unbalanced three-phase two sets of three-phase system,based on several typical unbalanced situation of operation data and comparing the simulation results and verify the effectiveness of the proposed three-phase imbalance of 10 kv additional loss affect the accuracy of the quantitative relationship between the distribution network.On this basis,the extended modeling analyzes the influence of different access positions and different access phases of three-phase load on the additional loss of 10 kV distribution network respectively.According to the quantitative analysis results and simulation results,it can be concluded that,compared with the increase trend of the additional loss rate on the side of 10 kV line with the unbalance degree,the increase rate of the additional loss rate on the side of 0.4kv line is the fastest.In addition to considering the negative sequence unbalance degree,the zero sequence unbalance degree and the line impedance should also be taken into account.According to the extended modeling analysis,the smaller the transformer capacity of unbalanced load is,the larger the additional loss rate will be.It is assumed that the first end of the feeder has the same degree of unbalance,and the unbalanced additional loss coefficient is also different when the unbalanced load is connected differently.