Study On Method Of Assessment For Winding Deformation And Losses Of Distribution Transformers

The distribution transformers are distributed widely and the equipment which connected to the users directly in the power system. According to the statistics, winding deformation accounted for a high proportion of transformer accident and the damage to the winding can be cumulated. Open-circuit loss and short-circuit loss are main parameters which can affect the performance and the efficiency of transformer. So realization the online detection of condition of transformer winding and loss is of great importance to the reality and the economy.In this paper, new detecting models of winding deformation and losses of distribution transformers are proposed. The short-circuit reactance and losses of distribution transformers are studied based on different connection types and the real operation characteristics. Meanwhile an evaluation model of winding deformation is presented based on fuzzy synthesis evaluation. The main work of the subject includes the following aspects:① The method for the short-circuit reactance of real-time operation transformers is proposed. The relationship among voltage, current and short-circuit reactance is obtained through studying the model of single-phase transformer. And then the short-circuit reactance of transformer in Yyn0 and Dyn11 connection is proposed based on their own characteristics and easy implementation.② The modified method for the short-circuit reactance of real-time operation transformers is proposed, because previous method needs to measure many parameters. Nevertheless the modified algorithm only detects the short-circuit reactance without the measuring of primary side current parameters.③ The simulation detection system for the short-circuit reactance is designed. The algorithms proposed in different connection are verified and analyzed under the influence of asymmetric loads, voltage deviation, load rate and harmonic alone or together.④ The fuzzy evaluation model of transformer deformation is proposed. On the base of theory of the relative membership degree, the weight coefficient and the general length, the target function is to minimize the sum of square distance. Calculate the relative membership of the evaluation indexes to evaluation standard, and then get the grade characteristic values and grade of the sample. The proposed evaluation model for winding deformation of distribution transformer is validated, according to the actual short-circuit reactance and winding deformation data.⑤ The modified online detecting method for the loss of distribution transformers is proposed. The modified loss monitoring method is proposed according to the equivalent circuit model under the fact that the short-circuit reactance can be calculated accurately and effectively. And then the online detection system for the loss is designed. The simulation experiment is done to verify the effectiveness by comparing with two typical online detection methods on it.Realize the online assessing of the transformer wingding’ state and transformers’ performance by monitoring the voltage and current signals, which provide a certain theoretical and method reference for the engineering practice.