Space Electromagnetic Optimization of Three-Coil WPT for Online Monitoring Equipment of High-Voltage Transmission Lines

In the context of a smart grid, sensors act as real-time monitoring devices. They enable the continuous assessment of the performance index for high-voltage transmission lines. Compared with the traditional lithium battery energy supply system, wireless power transmission (WPT) systems not only ensure the safety but also reduce the maintenance schedule. In the process of energy transmission, traditional insulator-clamped WPT systems are susceptible to interference from metal connectors. Moreover, electromagnetic energy leakage can pose threats to the safety of personnel working with charged equipment and the stable operation of nearby conductive sensing devices. This study analyzes the general principles of energy flow in multicoil WPT systems based on the Poynting's theorem. We introduce the energy contraction coefficients to analyze the distribution of electromagnetic energy in the three-coil systems Achieving energy confinement in the system by adding the relay coils. Combined with an engineering background, we establish constraints and optimize the relay coil's radius and position. We clarify the relationship between relay coil parameters and system energy confinement. Through simulations and experiments, it is shown that with a constant system output power, the optimized three-coil systems improve the energy contraction coefficient by 20.9% compared to the initial two-coil system and increase the magnetic flux density contraction coefficient by 19.4%. This effectively enhances the stability of energy transfer and the safety of the external electromagnetic environment in insulator-clamped WPT systems.