超临界机组高温高压管道焊缝内存在大量微小裂纹类缺陷，常规超声检测难以对该类缺陷进行准确测量和监控跟踪，故应采用多种方法进行检测。通过分析常规脉冲反射法、衍射时差法和超声相控阵法的工作原理，对比了三种方法的优缺点，并通过实际应用对比了三种方法的检测效果。经验证实，结合电厂实际生产需求，对特殊缺陷区域应增加TOFD和相控阵方法的检测。

Lots of micro-cracks were found in pipe butt welds in high temperature and high pressure of supercritical units. They should be tested by various detection methods because conventional ultrasonic testing was difficult in precise measurements of micro-cracks and in monitoring them. By analyzing the operating principle and contrasting the advantages and disadvantages between the three detection methods of ultrasonic, TOFD and phased array, and then the detection results of the three methods by practical application were contrasted. By empirical verification and considering the actual demands of the power plant, TOFD and phased array should be added to detect the special defect area.