Selection Basis For Current Transformers

Rated voltage
The rated voltage of the current transformer should be greater than the rated voltage of the line at the installation point [7].
Transformation ratio
The current transformer ratio should be selected based on the calculation of current IC based on the primary load. Standard ratio of rated current on the primary side of current transformers (such as 20, 30, 40, 50, 75, 100, 150, 2 × There are various specifications such as a/C), and the rated current on the secondary side is usually 1A or 5A. Among them, 2 × A/C indicates that there are two current ratios for the same product, which can be achieved by changing the connection method of the product. When connected in series, the current ratio is a/c, and when connected in parallel, the current ratio is 2 × A/C. In general, the selection of the conversion ratio of the current transformer for metering should ensure that its primary rated current I1n is not less than the load current in the line (i.e. IC calculation). If the calculated current of the load in the line is 350A, the conversion ratio of the current transformer should be selected as 400/5. To ensure the accuracy requirements of the current transformer used for protection, the transformer ratio can be selected to be larger.
Accuracy level
The accuracy level of the current transformer should be selected and verified according to the measurement accuracy requirements.