是短路电流的大峰值，开关隔离开关可以在不损坏的情况下闭合。当制造商未给出该值时，必须将其视为至少等于对应于Icw的峰值电流。由于不需要隔离开关来断开短路电流，因此不可能定义断开容量Icu[kA]。交流电和直流电的使用类别：定义使用条件的种类，使用两个字母表示设备可能安装的电路类型（交流为交流电，直流为直流电），两位数表示必须操作的负载类型，另加一个字母（a或B），表示使用中的频率。根据使用类别，产品标准定义了隔离开关在异常条件下必须能够断开和闭合的电流值。

is the maximum peak value of a short-circuit current which the switch disconnector can close without damages. When this value is not given by the manufacturer it must be taken to be at least equal to the peak current corresponding to Icw. It is not possible to define a breaking capacity Icu [kA] since switch disconnectors are not required to break short-circuit currents • utilization categories with alternating current AC and with direct current DC: define the kind of the conditions of using which are represented by two letters to indicate the type of circuit in which the device may be installed (AC for alternating current and DC for direct current), with a two digit number for the type of load which must be operated, and an additional letter (A or B) which represents the frequency in the using. With reference to the utilization categories, the product standard defines the current values which the switch disconnector must be able to break and make under abnormal conditions.