A Calculation Method of Zero Sequence Impedance of Distribution Transformer

Abstract

A method for calculating the zero-sequence impedance of a distribution transformer. When the three-phase load is unbalanced, the method obtains the operating electrical quantity of the distribution transformer through the acquisition device in the station area, establishes a voltage loop equation group of the zero-sequence impedance to be obtained, and converts the voltage The evaluation problem of circuit equations is transformed into the optimization problem of objective function, and the zero-sequence impedance of distribution transformer is calculated by applying genetic algorithm. The present invention aims at the situation that the zero-sequence impedance test is generally not performed in the factory test of the distribution transformer. On the basis of using the existing operating data of the distribution transformer in the station area, a nonlinear equation group containing the zero-sequence impedance to be obtained is established, and the nonlinear equation is considered. The group is difficult to be calculated by general numerical methods. The problem of solving nonlinear equations is transformed into an objective optimization problem, and the genetic algorithm is used to solve the objective optimization function. Finally, the zero-sequence impedance of distribution transformers under different zero-sequence currents is obtained.

Description

technical field [0001] The invention relates to a method for calculating the zero-sequence impedance of a power distribution transformer, which belongs to the technical field of transformers. Background technique [0002] The zero-sequence impedance of distribution transformers will affect the operation of 0.4kV low-voltage distribution network. When the three-phase load of the low-voltage distribution network runs in balance, the three-phase voltage will not shift. However, the three-phase load is often unbalanced in actual situations, and the existence of zero-sequence impedance of the distribution transformer makes the neutral point voltage appear. Offset, at least one phase of the load terminal voltage rises, and the user's household appliances are easy to burn out when operating under abnormal voltage. The value of zero-sequence impedance directly affects the degree of neutral point voltage offset. [0003] At present, the short-circuit impedance parameters of distribu...

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Problems solved by technology

[0005] The purpose of the present invention is to solve the problem that the zero-sequence impedance of distribution transformers is generally not tested in the factory, and the method of measuring zero-sequence impedance needs to be measured before it is put into operation, and cannot be calculated online. The present invention discloses a distribution transformer Calculation method of zero sequence impedance

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