本标准适用于电压等于或小于1000 V rms或1200 V dc的系统上应用的两个或三个端子、四层或五层晶闸管浪涌保护装置（SPD）。这些保护装置设计用于限制通信电路和从直流（dc）运行到420 Hz的电源电路上的电压浪涌。晶闸管SPD可采用单向或双向、对称或不对称V-I特性制造。本标准包含用于确定晶闸管SPD特性的定义、使用条件和一系列试验标准。如果特性与传导方向不同，则应单独规定每个极性。

This standard applies to two or three terminal, four or five layer, thyristor surge protection devices (SPDs) for application on systems with voltages equal to or less than 1000 V rms or 1200 V dc. These protective devices are designed to limit voltage surges on communication circuits and on power circuits operating from direct current (dc) to 420 Hz. The thyristor SPD can be manufactured with unidirectional or bidirectional, symmetrical, or asymmetrical V-I characteristics. This standard contains definitions, service conditions, and a series of test criteria for determining the characteristics of a thyristor SPD. If the characteristics differ with the direction of conduction, each polarity shall be separately specified.