Electrical power is, in most cases, not produced at the same location as it is consumed. The power grid connects power plants with end users and transports the electrical energy from production to consumers.
The power grid is organized into different voltage levels from a few hundred volts (LV), to several 10 kV (MV) up to several 100 kV (HV), depending on the amount of power transportation capacity needed.
The different voltage levels are interconnected by substations which contain voltage transformers, circuit breakers, surge arrestors, isolators etc. as well as other measurement equipment and switchgear.