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零序电流互感器为一种线路故障电流监测器。一般只有一个铁芯与二次绕组,使用时，将一次三芯电缆穿过互感器的铁芯窗孔，二次通过引线接至专用的继电器，再由继电器的输出端接到信号装置或报警系统。在正常情况下，一次回路中三相电流基本平衡，其所产生合成磁通也近于零。在互感器的二次绕组中不感生电流，当一次线路中发生单相接地等故障时，一次回路中产生不平衡电流（意即零序电流），在二次绕组中感生微小的电流使继电器动作，发生信号。这个使继电器动作的电流很小（mA级），称作二次电流或零序电流互感器的灵敏度（也可用一次最小动作电流表示），为主要动作指标。

Zero sequence current transformer is a kind of line fault current monitor. Only one core and two windings, when in use, will be the first three core cable through the transformer core fenestrae, two by wire connected to a dedicated relay, and then received by the relay output signal device or alarm system. Under normal conditions, the three-phase current in a primary circuit is basically balanced, and the resulting synthetic flux is near zero. In the two winding transformer in the induced current, when a line single-phase grounding fault, produce unbalanced current in the primary circuit (i.e., zero sequence current) in the two winding induced in small current relay signal. The current of the relay is very small (mA level), which is called the sensitivity of the two current or zero sequence current transformer (which can also be expressed by a minimum action current), which is the main index of action.

在10kV馈线开关柜中的位于开关内侧的电流互感器，视接线方式一般分为两相或三相。该电流互感器由一次绕组（L1、L2）和二次绕组、铁芯并有硅橡胶浇筑而成。

In the 10kV feeder switch, the current transformer located on the inside of the switch is generally divided into two phases or three phases. The current transformer is made up of primary winding (L1, L2) and two winding, iron core and silicon rubber.

电流互感器电流互感器是将一次设备的大电流转换成二次设备使用的小电流，其工作原理相当于一个阻抗很小的变压器。其一次绕组与一次主电路串联，二次绕组接负荷。电流互感器的变比一般为X/5A或X/1A（X不小于该设备可能出现的最大长期负荷电流），如此即可保证电流互感器二次侧电流不大于5A或1A。

Current transformer, current transformer is a primary device to convert large current into two devices using small current, the principle of operation is equivalent to a transformer with very small impedance. The primary winding is connected in series with the main circuit, and the two winding is connected with the load. The ratio of the current transformer is generally X/5A or X/1A (X is not less than the maximum long-term load current that may occur), so that the current of the two side of the current transformer is not greater than 5A or 1A.

在电厂和变电站中，如果高压配电装置远离控制室，为了增加电流互感器的二次允许负荷，减小连接电缆的导线界面及提高精确等级，多选用二次额定电流为1A的电流互感器。相应的，微机保护装置也应选用交流电流输入为1A的产品。

In the power plant and substation, if the high voltage distribution device away from the control room, two times in order to increase the allowed load current transformer, reducing the connecting cable wire interface and improve the precision level, more than two times the rated current of current transformer 1A. Accordingly, the microcomputer protection device should also choose the product with alternating current input of 1A.