How to protect power transformers from lightning

The power transformers we usually use, sometimes in thunderstorm weather distribution lightning accidents, mainly because of the distribution system when suffering lightning damage "forward and reverse conversion" overvoltage caused, and reverse conversion overvoltage damage accident, let's see how the power transformer lightning protection.
Positive conversion overvoltage When the low-voltage side line is struck by lightning, the lightning current invades the low-voltage winding and enters the ground through the neutral point grounding device, and the grounding current generates a voltage drop on the grounding resistance. This voltage drop causes the neutral point potential on the low side to rise sharply. It is superimposed on the low-voltage winding and overvoltage, endangering the low-voltage winding. At the same time, this voltage is increased to the high-voltage side by the electromagnetic induction of the high and low voltage windings according to the transformation ratio, and superimposed with the phase voltage of the high voltage windings, resulting in dangerous overvoltage in the high voltage windings. This phenomenon of overvoltage of the high-voltage winding caused by lightning overvoltage due to electromagnetic induction conversion to the high-voltage side is called "positive conversion" overvoltage.
Reverse overvoltage When the high-voltage side line is struck by lightning, the lightning current is discharged into ground through the high-side arrester, and the grounding current generates a voltage drop on the grounding resistor. This voltage drop acts on the neutral point of the low voltage side, and the low side outlet is equivalent to being grounded by resistance, so most of the voltage is added to the low voltage winding. After electromagnetic induction, this voltage drop is raised to the high-voltage side by transformation ratio, and superimposed on the phase voltage of the power transformer of the high-voltage winding, resulting in overvoltage of the high-voltage winding and causing a breakdown accident. This phenomenon of overvoltage of the high-voltage winding caused by lightning strikes on the low-voltage side, acting on the low-voltage side, and transforming to the high-voltage side through electromagnetic induction is called "reverse conversion overvoltage".