某变电站并联电抗器500 kV侧电容式电压互感器（CVT）附件L型接线板在台风中突然断裂，通过宏观形貌观察、化学成分分析、力学性能测试、显微组织观察、有限元模拟等方法对其断裂原因进行了分析。结果表明：该L型接线板的断裂性质为脆性断裂。接线板显微组织中存在的尺寸较大的长片状或板条状共晶硅和AlFeSi第二相是其断裂的主要原因，而结构设计不合理是其断裂的另一原因；在引线因受台风影响剧烈舞动产生的拉应力和扭矩作用下，微裂纹在接线板螺栓孔与CVT顶端凸台边缘接触处应力集中位置的粗大AlFeSi第二相颗粒处萌生，并沿脆性共晶硅相扩展，最终导致接线板发生脆性断裂。

The L-type junction board of the 500 kV side capacitor voltage transformer (CVT) accessory of shunt rector in a substation broke suddenly in a typhoon day. The fracture causes were analyzed by macro-morphology observation, chemical composition analysis, mechanical property test, microstructure observation and finite element simulation. The results show that the fracture property of the L-type junction board was brittle fracture.The large flake or lath eutectic silicon and the AlFeSi second phase in the microstructure of the junction board were the main causes of its fracture, and the unreasonable structure design was the other cause of its fracture. Under the tensile stress and torque caused by the violent movement of the leads in the typhoon environment, the microcracks initiated at the coarse AlFeSi second phase particles in the stress concentration location of the contact part between the bolt hole of the junction board and the edge of the convex platform at the CVT top, and then extended along the brittle eutectic silicon phase, eventually leading to brittle fracture of the junction board.