Method for detecting working point of current transformer under direct current magnetic biasing condition

Abstract

The invention discloses a method for detecting a working point of a current transformer under a direct current magnetic biasing condition. The method comprises the following steps of determining alternating current magnetic flux of the current transformer by a numerical integration algorithm; superposing one direct current magnetic flux on the alternating current magnetic flux, calculating a corresponding exciting current instantaneous value and a direct current exciting current average value according to a magnetizing curve of an iron core, and calculating the direct current magnetic flux of the iron core of the current transformer by utilizing an iterative approximation method to determine the characteristic quantity associated with the working point of the current transformer under the direct current magnetic biasing condition. The method disclosed by the invention can be used for calculating and determining the characteristic quantities of the sizes of the alternating current magnetic flux and the direct current magnetic flux of the iron core of the current transformer under the direct current magnetic biasing condition, the value of exciting current, the values of alternating current exciting current and direct current exciting current, the current transformer secondary current and the like associated with the working point of the current transformer.

Description

technical field [0001] The invention relates to a numerical calculation method for determining the working point of a current transformer under the condition of DC bias, including a calculation algorithm of the magnetic flux of the iron core of the current transformer and a system platform for detecting the working point of the current transformer, and belongs to the technical field of electric power automation. Background technique [0002] The distribution of DC potential in the earth may be formed by the operation of the single pole ground return line of the HVDC power transmission system or the solar magnetic storm, so that the DC current enters the AC grid from the transformer directly grounded at the neutral point, resulting in the DC bias magnetization of the current transformer of the AC system. DC bias may speed up the protection of current transformers, and the larger the bias current is, the faster the current transformers will saturate. [0003] The research on t...

AI Technical Summary

Problems solved by technology

According to research, under normal circumstances, a small excitation current can generate rated working magnetic flux. At this time, if a certain amount of DC enters the current transformer, the generated DC magnetic flux is much greater than the rated magnetic flux. If the two parts of the magnetic flux are directly Superposition, the main magnetic flux will be greatly shifted in one direction, resulting in high saturation of the iron core and serious distortion of the excitation current

For the DC bias phenomenon of current transformers, it is easy to misunderstand that the magnetic flux of the current transformer under the DC bias is equal to the DC magnetic flux generated by the DC current entering the current transformer directly superimposed on the original AC magnetic flux, Produce DC Bias Effect

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