经受住的不同电压值规定了三个等级,

即:I级:CTI大于600V;II级:CTI在400到600之间;III级:CTI在175到400之间

标准原文请参考:

2.10.4.2 Material group and comparative tracking index

Material groups depend on the comparative tracking index (CTI) and are classified as follows:

Material Group I CTI ≥ 600

Material Group II 400 ≤ CTI < 600

Material Group IIIa 175 ≤ CTI < 400

Material Group IIIb 100 ≤ CTI < 175

The material group is verified by evaluation of the test data for the material according to

IEC 60112 using 50 drops of solution A.

If the material group is not known, Material Group IIIb shall be assumed.