Abstract: There are many fire accidents in UHV converter station due to converter failure. The fire enters the valve hall through the plugging part of the casing at the converter valve side, which leads to the damage of the converter valve hall. In order to improve the fire safety margin of the converter station, this paper expounds the existing sealing structure form of the casing hole at the valve side of the converter transformer, and discusses the evaluation method of the fire resistance limit of the sealing structure. In view of the shortcomings of the existing sealing structure, and when the large sealing structure is not removed, the sealing structure is designed for fire resistance enhancement to form a new sealing structure enhancement system, and the fire resistance limit test is carried out according to the new evaluation standard. The results show that the enhanced system has good heat insulation performance and integrity, and meets the requirements of the fire resistance limit of the 3 h hydrocarbon temperature rise curve. It is a sealing structure for the casing at the valve side of the operation and exchange station to provide a solution for fire protection reconstruction.

Key words: valve-side bushings, plugging structure, evaluation method, fire resistance limit