The main difference is that the working state is very different during normal operation, which is shown as follows:
1) The current transformer can be short-circuited for the second time, but must not be open; the voltage transformer can be opened for the second time, but must not be short-circuited;
2) Compared with the load on the secondary side, the primary internal impedance of the voltage transformer is so small that it can be ignored. It can be considered that the voltage transformer is a voltage source; Mini Current Transformer
while the primary internal resistance of the current transformer is so large that it can be considered It is a current source with infinite internal resistance.
3) The magnetic flux density of the voltage transformer is close to the saturation value when the voltage transformer is working normally, and the magnetic flux density is reduced when the fault occurs; the magnetic flux density is very low when the current transformer is working normally, and the short-circuit current on the primary side becomes very large when the The flux density has increased greatly, sometimes far exceeding
The rated capacity of the current transformer is the apparent power consumed when the rated secondary current I2e passes through the rated load Z2e, that is, S2e=.
Generally I2e=5A, so S2e=25Z2e. In the use of current transformers, the accuracy of the secondary connection and the total impedance of the instrument current coil does not exceed the rated capacity (volt-ampere or ohm) specified on the nameplate.