Why should the secondary side of the current transformer not be open-circuited during operation? Hazards and Precautions After Open Circuit

(1) The secondary side of the operating current transformer must not be open-circuited for the following reasons: When the current transformer is operating normally, since the secondary side load impedance is very small and close to a short-circuit state, most of the magnetomotive force generated by the primary side current is Compensated by the counter-magnetomotive force generated by the secondary side current, the total magnetic flux density is not large and the electromotive force generated in the secondary winding is not large.
When the secondary side of the operating current transformer is open-circuited, the impedance becomes infinite, the secondary side current is zero, and no diamagnetic force is generated. The primary side current all becomes the excitation current, and the magnetic induction intensity in the iron core increases sharply. The iron core is seriously saturated, and the magnetic flux waveform will become a flat-top wave. When the magnetic flux changes from positive to negative or from negative to positive, the secondary side voltage is very high, and its peak value can reach several thousand volts.
(2)Hazards caused by opening the circuit:
1) The insulation between the secondary winding of the current transformer and the ground is designed for low voltage. When a large electromotive force is induced in the secondary winding, it will cause damage to the instrument, relay protection device, safety automatic device and the secondary side of the current transformer. Insulation damage seriously threatens the safety of people and equipment.
2) Since all the primary side current turns into excitation current, the magnetic flux density of the iron core will increase excessively and the iron core will be seriously overheated and damaged.
(3) Things to note when handling:
1) Relevant protection devices and safety automatic devices should be disabled before processing.
2) Insulated tools should be used for handling.
3) A short circuit should be made in front of the loop disconnection point to make the secondary side impedance of the current transformer zero.