在测量交变电流的大电流时,为便于二次仪表测量需要转换为比较统一的电流（我国规定电流互感器的二次额定为5A或1A），另外线路上的电压都比较高如直接测量是非常危险的。电流互感器就起到变流和电气隔离作用。 它是电力系统中测量仪表、继电保护等二次设备获取电气一次回路电流信息的传感器，电流互感器将高电流按比例转换成低电流，电流互感器一次侧接在一次系统，二次侧接测量仪表、继电保护等。 In the measurement of alternating current high current, for ease of secondary instrument measuring need into a more uniform current (regulation in our country current transformer secondary rated as 5 a or 1 a), the other on a line voltage is higher, such as direct measurement is very dangerous. Current transformer ACTS as transformer and electrical isolation. It is measuring instrument, relay protection in power system secondary equipment such as electric a loop current information sensor, current transformer to convert high current in proportion to the low current, current transformer primary side in a system, secondary side by measuring instrument, relay protection, etc. PS：电流互感器接被测电流的绕组（匝数为N1），称为一次绕组（或原边绕组、初级绕组）；接测量仪表的绕组（匝数为N2）称为二次绕组（或副边绕组、次级绕组）。 PS: current transformer (N1), called a winding (or primary winding, primary winding). The winding of the measuring instrument (N2) is called a secondary winding (or subside winding, secondary winding). 电流互感器原理是依据电磁感应原理的。电流互感器是由闭合的铁心和绕组组成。它的一次绕组匝数很少，串在需要测量的电流的线路中，因此它经常有线路的全部电流流过，二次绕组匝数比较多，串接在测量仪表和保护回路中，电流互感器在工作时，它的2次回路始终是闭合的，因此测量仪表和保护回路串联线圈的阻抗很小，电流互感器的工作状态接近短路。电流互感器是由一次高电压转换成二次低电压来使用二次不可开路。 The principle of current transformer is based on the principle of electromagnetic induction. A current transformer consists of a closed core and winding. It's a little winding circle number, string in the current need to measure the line, so it often have all the current flows through the line, the secondary winding circle number is more, concatenated in measuring instrument and protection circuit, current transformer at work, it's two loop is always closed, so the measuring instrument and protection circuit in series with the coil impedance is very small, the working state of the current transformer is close to a short circuit. The current transformer is converted from a high voltage to a secondary low voltage to use a secondary unopened circuit.