When the power supply system is in normal operation, the insulation of the electrical equipment is under the rated voltage of the power grid, but due to the lightning strike, the voltage of some parts of the power supply and distribution system will greatly exceed the value under normal conditions, and the power is usually changed. There are two cases of lightning strikes: one is that the lightning strikes directly on the equipment of the substation; the other is that the lightning induced overvoltage of the overhead line and the lightning wave formed by the direct lightning strike overvoltage invade the substation along the line. Its specific manifestation is as follows:
1. Directly hit the lightning over voltage. When Lei Yun hits the power device directly, a powerful lightning current is formed. The lightning current generates a high voltage on the power device. When the lightning current passes through the object, it will produce a destructive thermal effect and mechanical effect.
2. Inductive overvoltage. When the thundercloud is above the overhead conductor, due to static induction, a large amount of opposite-charged charges accumulate on the overhead conductor. When the thundercloud discharges to the earth, the charge on the line is released, and the free charge formed flows to both ends of the line. High overvoltage, this overvoltage can cause damage to the power network.
Therefore, the lightning induced overvoltage of the overhead line and the lightning wave formed by the direct lightning strike overvoltage invade the substation along the line, which is the main cause of lightning damage in the substation. If no protective measures are taken, it will inevitably cause insulation of the electrical equipment of the substation. Damage, causing an accident.