Triboelectric nanogenerators (TENGs) show potential for powering distributed sensors in the smart grids. However, most studies on TENG's applications for energy harvesting from transmission lines primarily focus on vibration and wind energy, neglecting the abundant electric-field energy from transmission systems. This study proposes a triboelectric-electrostatic hybrid energy harvester (TEHEH) that integrates a triboelectric nanogenerator with an electric-field energy harvester (EFEH) to simultaneously capture wind energy and electric-field energy from the surroundings of transmission lines. The TENG and EFEH can generate open-circuit voltages of 1280 and 2800 V, respectively, with output powers of 14.3 and 28.9 mW. Hybrid energy harvesting achieves an average power of 6.1 times that of TENG and 2.4 times that of EFEH, demonstrating its superiority. The dual-channel energy management circuit, utilizing a gas discharge tube and the LTC-3588, enables the hybrid nanogenerator to effectively power a wireless sensor node, demonstrating its practicality in the complex environments of power transmission lines. This work offers robust technical support for the development of self-powered monitoring devices on high-voltage transmission systems.