Why do electric devices get burnt during thunderstorms

[antonantal]

Why do electric devices that use the wall plug get burnt sometimes during thunderstorms? Is it because the lightning changes the potential of the ground in the area surrounding the point where it strikes to a lower than 0 (reference) level potential, thus increasing the voltage of the wall plugs of a house in that area?

Also I read on a website that

"The movement of air and charged cloud particles within them separates electrical charges vertically; lightning then transfers the extra electrons at the base of the cloud to the ground."

My question is: Since the electric charge of the solid Earth is negative how come that the charges in the clouds separate so that the negative ones are at the base?

 

[cesiumfrog]

More likely because it strikes a line directly, producing a surge.