They have the function of reducing Medium Voltage to Low Voltage used by the end domestic, commercial or small industrial consumer.
There are 2 different types. enclosed within a stonework construction, or even in a metallic box, or suspended on a post in the air.

They are used to raise the power of the electricity produced in the power stations to be transported as high voltage to consumer areas, and once near to the consumer areas, the voltage is lowered so that it can be distributed as medium voltage.
These installations contain gates where the lines originate and end, as well as the electrical potential transformers and protection accessories.
These installations are protected by a fence, with signs warming of the danger of electricity inside and forbidding access to unauthorised personnel.

They take electricity from the Transforming Stations along the roads and paths to locations which use Low Voltage (230 V single-phase and 400 V dual-phase). These may be 2 types: overhead or underground.
Overhead lines may be naked conductors or insulated in a bundled (stranded cable)
Lines with a plain conductor are fixed over insulators and supported on concrete posts, or over small metallic structures placed on the façade.
Low-voltage distribution cables normally consist of five conductors, one of which is utilised for public lighting.

They are those whose nominal voltage is less than 60 kV. The most frequent voltages are 10, 15 and 30 kV. These lines link substations to Transforming Substations or link different Switching/Transforming Stations/ to each other.
They may be overhead or underground. Overhead lines are normally naked cables, supported on concrete posts (most frequently), or metallic posts, with the conductors suspended or supported by insulators.

They are those whose nominal voltage is equal or greater than 60 kV.
These lines join generating centres (thermal, hydrological, wind plants) to substations or between a number of substations. They are usually overhead lines but can be underground. Overhead lines use supports, which are normally metallic, with the conductors suspended or supported by insulators.