Surges in electrical installations are divided into two groups:
This division relates to causes of these surges.
Internal surges take place inside electrical installations, e.g. as a result of switching currents, damage to electrical installation or sudden load change. They are further divided into:
The second group includes atmospheric surges caused by environmental phenomenon, mainly by atmospheric discharges. Their division depends on the distance from electrical installation. The strongest surges are caused when a lightning directly strikes electrical installation. In the second place there are surges caused when a lightning strikes in close proximity to electrical installation. Atmospheric discharges that take place between clouds are less significant; of course, the closer the distance to electrical installation, the stronger the discharge. Atmospheric discharges can also be caused by radio waves.
Division of surges can also be based on their duration: they can be pulsed or long-lasting.