Power grid companies need to carry out power maintenance, testing, and fault diagnosis on transmission lines in the case of large-scale power outages. This method is inefficient, affects the normal operation of the power grid, and will cause huge economic losses. Therefore, there is an urgent need for a more portable, sensitive, and efficient cable flaw detection method. Due to the high material density of transmission lines, X-ray sources with high energy and intensity are required. To address this problem, this paper presents a design scheme for an X-ray generator with low radiation, low power consumption, and high voltage. Use radiation protection beam to improve metering efficiency which can reduce radiation, and design the overall structure of power supply and filament power supply. Finally, the feasibility of high voltage X-ray detection technology in transmission line defect detection is proved by experiments. This paper provides a new idea for transmission line fault diagnosis, which has great social benefits and application prospects.