Power surges can be caused by the power company itself or the power surges may also be caused by something in your home or even lightning.
The most common cause of power surges is because the power company or utility company switches the power around known as power grid switching.
Or when the utility requires more electricity to flow through the utility lines due to huge demand such as in the summer months when the air conditioners are all running.
That can then cause a power surge when the electricity suddenly gets a jolt of energy to supply those air conditioners and other appliances etc.
Even your own air conditioners such as window air conditioners, central air conditioners etc can all cause a temporary power surge.
Air conditioners including both window air conditioners and central air conditioners all require a lot more power to start the compressor than they do to keep them running.
So you may also notice your lights in the house dim out when you turn on your window air conditioner or central air conditioner.
That's because of the high amp draw of the ac compressor to get started.