The Power grid is the complete energy line from the Production to the end users, and it is basically divided into High Voltage Transmission line and Distribution network.
In order to transport great quantity of Energy from the place of Production (Power station) to the end users (factories, houses, etc.), reducing cable sizes and losses, the tension is immediately increased at the generating place with a so called Step Up Transformer.
Depending on the country standards and distances to run, the high voltage tension can be then brough to 400 Kv till 800 or 1000 Kv, various transmission other transformers (either Step up or Step down) may be then used to interconnect portions of national and international power grids, and to move generated energy where needed at that moment with voltages of about 100 Kv to 220 Kv.
A step down transformation is then made for the Large industry use, or for entering into cities with a first Step Down Transformer bringing the tension generally below 35 Kv
All the power line transformed below the voltage of 35 Kv is called Distribution network, which is formed by a bigger number of transformation points and cables to serve the needs of energy from the factories and houses.
THE FUTURE OF POWER GRIDS HVDC
Most of the world's electric power networks supply alternating current; however, major losses occur during AC transmission. Losses are less pronounced in the transmission of direct current. New technologies ensure the efficient transmission of electricity via High Voltage Direct Current (HVDC) networks, which immediately lowers line losses.The demand of HVDC transmission has greatly intensified, and specifically for connecting alternating current networks to new sources of power supply, such as offshore wind park.
The installations comprise AC/DC and DC/AC converter substations where alternating current is converted into direct current or vice-versa. Because of the extremely high cost of special substations for DC, transmission of this type is only feasable over very long distaces or for submarine power cables.