Why can't the voltage transformer be short-circuited?

The voltage transformer cannot be short-circuited because the internal impedance of the voltage transformer is very small. If the secondary circuit is short-circuited, a large current will appear, which will damage the secondary equipment and even endanger personal safety.
The voltage transformer can be equipped with a fuse on the secondary side to protect itself from damage due to a short circuit on the secondary side. If possible, a fuse should also be installed on the primary side to protect the high-voltage power grid from endangering the safety of the primary system due to a fault in the transformer's high-voltage winding or lead.