What are the reasons for the bad voltage and current of low-frequency transformer?

The most common thing is that the surrounding equipment is often started, generating instantaneous surge current, which is fed back to the nearest power grid or connected power grid equipment to generate surge current. When some sensing devices stop instantly, it will produce instantaneous high voltage, and surge voltage will appear when feedback. There is also the current frequency conversion equipment. The equipment connected to it is not well shielded, which leads to space electromagnetic interference and directly affects the power supply of surrounding equipment.