I. Introduction
With the development of social economy, the total mileage of transmission lines in China is increasing. By 2018, the total length of 35kV and above transmission lines in China has reached 1.892 million kilometers, ranking first in the world. However, with the increase of transmission line length, the risk of external damage is also increasing, especially in some “three span” environment. Once the transmission line accident occurs, it will have a significant impact on the surrounding systems and economy. In recent ten years, with the development of artificial intelligence technology, more and more equipment equipped with real-time monitoring and image recognition technology appear in the transmission line monitoring system [1], [2]. Through the real-time acquisition of transmission line surrounding images and video information, artificial intelligence technology realizes the early warning of external damage [3], [4]. However, artificial intelligence technology only provide target category and position information on the image, and can not further obtain important information such as the distance between dangerous objects and transmission lines. Therefore, it needs to be realized with the help of multi domain technology of comprehensive image recognition.