为得到GIS(气体绝缘开关)内部缺陷(如开关合闸不到位)的尺寸，以给失效分析提供定量依据，结合X射线数字直接成像(DR)系统的Rhythm软件，从理论上提出了一套DR技术实物尺寸的计算方法，并进行了试验验证。在GIS现场检测中，根据拍摄得到的X射线图片，利用上述方法计算了GIS内部螺栓的尺寸以及触头与触座之间的间隙；经过与实物比对，发现计算结果与实际尺寸吻合。实践表明，提出的基于DR检测技术的GIS尺寸标定方法是有效的，其为定量分析GIS内部缺陷尺寸提供了依据。

In order to obtain the real size of flaws(e.g. the switch closing is not in place) inside Gas Insulated Switch(GIS) and provide quantitative evidence for failure analysis, in this paper, we theoretically presented and experimentally verified a method that can give the real size of parts inside GIS using the Rhythm software of X-ray Direct Radiography(DR) system. During the spot testing of GIS, with the obtained X-ray photographs, we calculated the size of screw and the gap between the contactors inside GIS by using the above method. Via contrast between calculated size and real size, we found that they were almost the same. These applications suggest that the method referred in the paper is effective, which provides quantitative solutions to those problems such as the flaws of GIS.