A method for measuring residual magnetism in power transformers based on leakage flux response

By employing a power transformer residual magnetism measurement method based on leakage flux response, and utilizing bipolar short pulse signals and polynomial fitting techniques, the magnitude and polarity of residual magnetism are accurately detected, solving the problem of low measurement accuracy in existing technologies and ensuring power grid safety.

CN122131205APending Publication Date: 2026-06-02CHINA YANGTZE POWER
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Patent Information

Authority / Receiving Office
CN Β· China
Patent Type
Applications(China)
Current Assignee / Owner
CHINA YANGTZE POWER
Filing Date
2026-03-20
Publication Date
2026-06-02

AI Technical Summary

Technical Problem

Existing methods for measuring residual magnetism in power transformers cannot accurately detect the magnitude and polarity of residual magnetism, and the measurement accuracy is low in low residual magnetism scenarios, which affects the safety of the power grid and the normal operation of equipment.

Method used

A method for measuring residual magnetism in power transformers based on leakage flux response is adopted. The method involves pre-charging the magnetic flux density by exciting with DC current, applying a bipolar short-pulse small voltage signal to trigger the transient leakage flux signal, measuring the tangential component of leakage flux in the air using a sensor, and determining the polarity and magnitude of the residual magnetism by combining polynomial fitting and data processing.

Benefits of technology

It enables accurate detection of residual magnetism, reduces measurement errors, ensures that inrush current is avoided when the transformer is switched on, and guarantees the safe operation of the power grid.

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Abstract

This invention provides a method for measuring residual magnetism in power transformers based on leakage flux response, relating to the field of transformers. The method first demagnetizes the transformer and pre-charges it with DC current to set the residual magnetism. Under no-load conditions, a bipolar short-pulse small voltage excitation is applied. The tangential component of leakage flux in the air is collected at a distance of 3-5 times the maximum length of the transformer's horizontal centerline. The average leakage flux under different residual magnetism conditions is calculated, and a decentralized leakage flux is obtained. The relationship curve between the forward adjustment time and the residual magnetism is extracted, a polynomial fitting formula is constructed, and the coefficients are determined. The polarity of the residual magnetism is determined by the difference in adjustment time under different polarity excitations. Finally, leakage flux information is collected for transformers with unknown residual magnetism and substituted into the formula to calculate the residual magnetism. This method is a non-invasive measurement, requiring no transformer disassembly, and can accurately detect the magnitude and polarity of residual magnetism. It is suitable for low residual magnetism scenarios, has low measurement error, and provides data support for suppressing inrush current and ensuring the safe operation of the power grid.
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