(1) lightning mainly simulates the indirect ray): for example, the lightning hit the outdoor line, there are a lot of current into the external circuit or grounding resistance, resulting in disturbance voltage; also, the indirect lightning (such as clouds or clouds of lightning) or current voltage induced on the line; moreover, lightning struck nearby the object, at the periphery of a magnetic field, when the outdoor line through the electromagnetic field, on the line induced voltage and current; also as lightning struck the ground around, the current through the public interference grounding system introduced.

(2) switching transients: for example, the main power supply switching system (such as switching compensation capacitor group) interference; again, the same power, there are some large interference switch formed by beating the near around the equipment; again, switching thyristor resonant line pipe equipment; also, all kinds of fault system, such as network equipment grounding or earthing system between the short-circuit or arcing fault.
Switching power supply can not be damaged after lightning surge. Two general types, "lightning" and "ringing" wave.