Method for calculating zero-sequence impedance of distribution transformer

Abstract

The invention discloses a method for calculating the zero-sequence impedance of a distribution transformer, and the method comprises the steps: obtaining an operation electrical quantity of the distribution transformer through a station zone collection device during three-phase load unbalance, building a voltage loop equation set of a zero-sequence impedance to-be-solved quantity, converting a solving problem of the voltage loop equation set into an optimization problem of a target function, and calculating the zero-sequence impedance of the distribution transformer through a genetic algorithm. Aiming at a condition that the zero-sequence impedance of the distribution transformer is usually not tested during a delivery test, the nonlinear equation set comprising the zero-sequence impedanceto-be-solved quantity is built on the basis of the existing operation data of the distribution transformer in a station zone. Considering that the nonlinear equation set is difficult to solve througha common numerical method, the method enables the solving problem of the nonlinear equation set to be converted into a problem of target optimization, and the genetic algorithm is used for solving the target optimization function. Finally, the zero-sequence impedance of the distribution transformer is solved under different zero-sequence currents.

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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