Research on the Residual Magnetic Flux Density Measurement of Single-Phase Transformer Based on Magnetomotive Force

Accurately measuring the residual magnetism of a transformer is a prerequisite for developing its closing strategy to suppress inrush current. The existing methods mostly establish a function between response and remanence by applying excitation to transformer's winding. However, when there is less residual magnetic flux in iron core, the response does not change significantly with residual magnetism, resulting in low measurement sensitivity and severely limiting the engineering application of such methods. To solve this issue, this article proposes a remanence measurement method based on magnetomotive force, by establishing the function between the integral of magnetomotive force and iron core's remanence under short-term pulse voltage. It can precisely measure residual magnetism throughout transformers' entire residual magnetization range, especially solving the problem of low measurement sensitivity under small residual flux density. The proposed method was experimentally validated on the ring transformer and the single-phase two-column transformer, and it can effectively improve the measurement sensitivity under low remanence, with an average measurement error of less than 0.05 T in the entire remanence range.