Operational requirements of miniature current transformers

First of all, the miniature current transformer must not exceed the rated capacity for long-term operation. This is because long-term overload, that is, the passing current exceeds the rated current of the current transformer, will cause the error to increase and the meter indication is incorrect. It may also cause overheating of the iron core and windings, rapid insulation aging, and even damage to the current transformer.

Secondly, during the operation of the miniature current transformer, care should be taken to keep its secondary side circuit always in a closed state. When removing the ammeter and other instruments from the CT in operation, the secondary winding should be short-circuited first; if the secondary winding is not used, it should be short-circuited. In addition, the secondary circuit of the current transformer must have one and only one grounding point. 

Third, in practical applications, one side of the secondary coil of the miniature current transformer and the iron core need to be grounded at the same time. The grounding of the secondary side of the CT is a protective grounding to prevent the breakdown of the primary and secondary windings due to insulation damage, and the secondary windings will be connected to high voltage, which will endanger the equipment and personal safety. It should be noted that when the secondary circuit of the current transformer is switched, the corresponding protection device should be disabled; it is strictly forbidden to open the circuit during operation. 

Fourth, in the circuit system, if the protection and instrument use a set of miniature current transformers, when the meter circuit is working, it should be noted that it must be short-circuited on the meter itself, and be careful not to open the circuit and do not connect the protection circuit Short circuit. At the same time, when working on site, the short-circuit location and safety measures should be determined according to the actual wiring. If there is zero-sequence protection, high-frequency protection, etc. in the same circuit, it should be disabled before the short-circuit.