电流互感器的二次额定电流有5 A 和1 A 两种。
The secondary rated current of current transformer is 5A and 1A.
二次额定电流为1 A 的电流互感器其特点是带负载能力强、准确限制高，适用于系统短路容量较大的环境下。但是较小的二次额定电流会对保护和计量装置产生不利影响，要求装置有很高的灵敏度。
Current transformer with secondary rated current of 1A is characterized by strong load capacity and high accuracy limit, which is suitable for the environment of large short-circuit capacity of the system. However, smaller secondary rated current will have adverse effects on protection and metering devices, requiring high sensitivity.
现在国内主流的微机保护装置内的电流变换器的精确工作范围一般为0.1 ～ 20I2n ,当输入装置的电流大于20 倍的额定电流时，所得到的数据准确性将很难得到保障。如果选择二次额定电流为1A的互感器，一定要考虑到保护定值能否整定，要校核保护定值的大小是否在保护装置的整定范围内。
At present, the precise working range of current converters in mainstream computer protection devices in China is generally 0.1~20I2n. When the current of the input device is greater than 20 times the rated current, the accuracy of the data obtained will be difficult to be guaranteed. If a transformer with secondary rated current of 1A is selected, it is necessary to consider whether the setting value of protection can be set, and to check whether the setting value of protection is within the setting range of the protection device.
根据工程实际选择，一般情况可选择5 A。
According to the actual selection of the project, 5A can be chosen in general.