电流互感器的作用是来使电表正常工作保护电表的。大家知道电表的电流是受电表的电路限制不能承受太大的电流的，所以就用电流互感器来降低电表的电流。那么电流互感器接在哪个部位呢，准确的回答是接在电表进线的那一级上。如果接在出线的位置，那就失去了互感器的作用了。只有把互感器接在进线（也就是电源进入电表的线路，而不是接在从电表到用户的线路上）当电流通过电源电流进入电流互感器，电流就会通过耦合作用产生一个小的电流（按照一定的比例）进入电脑（而不是电源线进入电表），小的电流使电表工作。电表工作的数值乘以互感器的比数，就是用户的实际用电量。
The function of current transformer is to make the meter work normally and protect the meter. We all know that the current of the meter is limited by the circuit of the meter and can't bear too much current, so we use current transformer to reduce the current of the meter. So where is the current transformer connected? The accurate answer is at the level of the incoming line of the meter. If it is connected to the outgoing line, it will lose the function of the transformer. Only when the transformer is connected to the incoming line (that is, the line from the power supply to the meter, rather than the line from the meter to the user), when the current enters the current transformer through the power supply current, the current will generate a small current (in a certain proportion) through the coupling effect and enter the computer (rather than the power line into the meter), and the small current will make the meter work. The actual power consumption of the user is the value of the meter multiplied by the ratio of the transformer.
电流互感器原理和变压器原理是一样的，都是利用电磁感应原理制作的。电流互感器一次侧只有一匝或几匝，二次侧有很多匝并且二次侧有两个接线端子S1S2。其中S1端子接电表电流线圈进线，S2端子接电表电流线圈出线。如果电表是三相四线制电表，那么电表里三个电流线圈的出线短接后接地。防止电流互感器损坏时一次侧高电压窜入二次侧，影响设备及人员安全。
The principle of current transformer is the same as that of transformer, which is made by electromagnetic induction principle. The primary side of current transformer has only one or several turns, the secondary side has many turns and the secondary side has two terminals S1S2. S1 terminal is connected with the incoming line of ammeter current coil, S2 terminal is connected with the outgoing line of ammeter current coil. If the meter is a three-phase four wire meter, the outgoing lines of three current coils in the meter shall be short circuited and grounded. Prevent the high voltage of primary side from entering the secondary side when the current transformer is damaged, which will affect the safety of equipment and personnel.