Simulation and Theoretical Study on the Mutual Inductance of the B-Dot Used for High-Power Transmission Lines

For the B-dot used for high-power transmission lines, due to its special structure, the current method to obtain its mutual inductance is calibration experiments and there lacks an effective method to estimate its mutual inductance at the design stage. In this article, the mutual inductance of this kind of B-dot is studied by simulation and theoretical analysis. Through simulation, the frequency response of the mutual inductance is obtained and it is found that the mutual inductance at high frequency which is the main working frequency range of the B-dot is the lowest and stable. Through theoretical analysis, the approximate calculation formula of mutual inductance at any frequency is derived. Using the experimental results in the previous reference, the theoretical results and the simulation results are verified. The influencing factors of the B-dot’s mutual inductance at high frequency are analyzed. The results show that the number of wire loops, the inner radius of wire loops, and the radius of the hole are positively related to the mutual inductance, and the height of the center of the wire loops is negatively related to the mutual inductance. Among these four factors, increasing the inner radius of wire loops can improve the mutual inductance more significantly. The work in this article reveals the physical meaning of the mutual inductance change and provides guidance for the design of the B-dot.