What are the characteristics of excitation inrush current in voltage transformer?

2025-10-23 15:07:04

Excitation inrush current refers to the total magnetic flux in the iron core before the Electronic Power Transforme is put into operation, which far exceeds the saturation magnetic flux of the iron core when the residual magnetic flux in the iron core is in the same direction as the magnetic flux generated by the operating voltage when the voltage transformer is put into operation. Therefore, a large inrush current is generated, and the peak value can reach 6-8 times the rated current of the Voltage changer.

The magnitude of the excitation surge and the percentage of the no-load current after stabilization are called surge multiples. If it does not decay completely within one hundred cycles, it is called the initial surge, and if it decays completely, it is called the steady-state surge. Due to the fact that inrush current is a short duration current, there is no clear useful value, only an instantaneous value is represented. Therefore, accurately speaking, it should be referred to as the peak value of inrush current.

To prevent the impact of voltage changer excitation surge on the power system, the following measures can be taken:

1. The residual magnetic flux in the iron core before input is less than the saturation magnetic flux of the iron core;

2. The residual magnetic flux in the iron core before input is in the opposite direction to the magnetic flux generated by the operating voltage of the voltage changer during input;

3. Adopt differential relays with fast saturated iron cores.