第一步、确定电压等级。 最好依据系统标称电压（即通常说的母线电压）来选择。常见系统标称电压就三种，6kV、10kV、35kV。其它电压等级仅偶尔会出现。 第二步、确定结构特征。 有间隙优于无间隙，但高原用（海拔2000m以上）除外。 阻容结构优于氧化锌结构，但电容保护用除外。 第三步、确定保护对象。 A型为弱绝缘类保护（如保护电动机，有的厂家称D型） B型为常规电器类保护（如保护变压器，有的厂家称S型、Z型或P型） C型为大能量冲击类保护（如保护电容器，有的厂家称R型） 第四步、确定使用场所。 户内型：用于开关柜内，要求尺寸小、中性点绝缘好。 户外型：用于站内露天，要求尺寸大、防污闪能力高。

The first step is to determine the voltage level. It is best to choose the system based on the nominal voltage (usually the bus voltage). The common system nominal voltage is three kinds, 6kV, 10kV, 35kV. Other voltage levels only occasionally appear. The second step is to determine the structural features. The gap is better than the no gap, but the plateau is excepted (above 2000m above sea level). The resistance capacitance structure is superior to the Zinc Oxide structure, except for the use of capacitance protection. The third step is to determine the protection object. A type insulation protection weak (such as motor protection, some manufacturers are called type D) type B for conventional electrical protection (such as transformer protection, some manufacturers called S type, Z type or P type) type C for energy impact protection (such as protection of capacitor, some manufacturers are called type R) fourth determine the use place. Indoor type: in the switch cabinet, the requirements of small size, neutral point insulation. Outdoor type: it is used in the open air of the station, which requires large size, high pollution flashover ability.