Precautions for current transformers

Current Transformer - Precautions for use When the current transformer is running, the secondary side is not allowed to open. Because once the circuit is opened, the primary side current becomes the excitation current, which makes the magnetic flux and secondary side voltage greatly exceed the normal value and endangers the safety of people and equipment. Therefore, it is not allowed to connect fuses in the secondary circuit of the current transformer, and it is not allowed to remove the ammeter, relay and other equipment without bypassing during operation.

When the current transformer is running, the secondary side is not allowed to open circuit. The reasons are as follows:

⒈ The primary measured current magnetic potential I1N1 of the current transformer generates a magnetic flux Φ1 in the iron core

⒉ The current magnetic potential I2N2 of the secondary measuring instrument of the current transformer generates a magnetic flux Φ2 in the iron core

⒊ Current transformer core combined magnetic flux: Φ = Φ1 + Φ2

⒋ Because Φ1.Φ2 are opposite in direction, equal in size and cancel each other, so Φ = 0

⒌ If the secondary open circuit, that is, I2 = 0, then: Φ = Φ1, the magnetic flux of the current transformer iron core is very strong, saturated, the iron core heats up, the insulation is burned out, and leakage occurs

⒍ If the secondary open circuit, that is, I2 = 0, then: Φ = Φ1, Φ generates a high induced potential e in the secondary coil N2 of the current transformer, and a high voltage is formed at both ends of the secondary coil of the current transformer, endangering the operation. Personnel life safety

⒎ One end of the secondary coil of the current transformer is grounded, which is a protective measure to prevent the danger of high voltage.