How to protect the power transformer from lightning?

The power transformers we usually use sometimes have lightning damage accidents in distribution transformers during thunderstorms, mainly due to the overvoltage of the forward and reverse transformation when the power distribution system suffers from lightning damage, and the reverse transformation overvoltage damage accident. See how power transformers are protected against lightning.

Positive transformation overvoltage When the low-voltage side line is struck by lightning, the lightning current penetrates into the low-voltage winding and enters the ground through the neutral point grounding device, and the grounding current produces a voltage drop on the grounding resistance. This voltage drop causes a sharp rise in the neutral point potential of the low-voltage side. It superimposes the overvoltage on the low-voltage winding and endangers the low-voltage winding. At the same time, this voltage is raised to the high-voltage side according to the transformation ratio through the electromagnetic induction of the high- and low-voltage windings, and superimposed with the phase voltage of the high-voltage winding, resulting in a dangerous overvoltage in the high-voltage winding. This phenomenon that the low-voltage winding is subjected to lightning strike overvoltage and is transformed to the high-voltage side through electromagnetic induction, causing the overvoltage of the high-voltage winding is called  positive transformation overvoltage.

Inverse conversion overvoltage When the high-voltage side line is struck by lightning, the lightning current is discharged into the ground through the high-voltage side arrester, and the grounding current produces a voltage drop on the grounding resistance. This voltage drop acts on the neutral point of the low-voltage side, and the low-voltage side outgoing line is equivalent to grounding through a resistor at this time, so most of the voltage is applied to the low-voltage winding. After electromagnetic induction, this voltage drop increases to the high-voltage side with a transformation ratio, and is superimposed on the phase voltage of the power transformer of the high-voltage winding, resulting in an overvoltage in the high-voltage winding and a breakdown accident. The phenomenon that the high-voltage side is struck by lightning, acts on the low-voltage side, and is transformed to the high-voltage side by electromagnetic induction, causing the overvoltage of the high-voltage winding, which is called inverse transformation overvoltage.

The use of power transformers should not only pay attention to the forward and reverse conversion, but also the lightning protection of the distribution transformer.