Protective current transformers are generally used in relay protection circuits where multiple busbars pass through. They are developed to detect short-circuit faults for the protection system, featuring different accuracy levels and accuracy limit factors, and can be extended to accommodate different hole sizes. They are widely used in low-voltage distribution protection systems. They can also be used to collect low-voltage overload and short-circuit signals and are used in conjunction with protective relays.

Product advantages

The structure is novel, the design is aesthetically pleasing, the installation is convenient, the size is compact, the weight is light, the accuracy is high, and the capacity is large.

structural characteristics

The shell is made of flame-retardant and heat-resistant imported polycarbonate, which can withstand temperatures up to 140°C, and is injection molded. The iron core is wound using oriented cold-rolled silicon steel strips, and the secondary conductors are made of high-strength electromagnetic enameled wire.

The working principle of a current transformer is illustrated in Figure 1. The primary winding of the current transformer is connected in series with the measured line. I1 represents the line current, which is also the primary current of the current transformer. N1 denotes the number of primary turns of the current transformer. I2 represents the secondary current of the current transformer (typically 5A or 1A), and N2 denotes the number of secondary turns of the current transformer. Z2e represents the impedance of the secondary circuit equipment and connecting wires. When the primary current flows into the current transformer from terminal P1 and out from terminal P2, and the secondary Z2e is connected, according to the principle of electromagnetic induction, a current I2 flows through the secondary winding of the current transformer from S1, through Z2e to S2, forming a closed loop. From this, it can be deduced that under ideal conditions, I1×N1=I2×N2, so I1/I2=N2/N1=K, where K is the transformation ratio of the current transformer.