The power is then carried to distribution substations or directly to very large industrial consumers. Power from the transmission system is then stepped down to a considerably lower voltage (say 33 to 66kV) using a step-down transformer in a primary step-down substation. Also, HVDC link is the only option today for interconnecting grids with different frequencies. AC power is converted into HVDC at a converter station for the transmission, and then it is converted back into AC at the other end. So, HVDC transmission systems are being employed for very longer distance power transmission. But due to the advancements in power electronics, HVDC (High Voltage DC) has proved many advantages for longer distance transmission. Most commonly 3-phase AC power at very high voltage is used for the power transmission. Transmissions lines are often seen running over tall towers at the outskirts of a city. Transmission voltages are generally 220kV or greater up to 765kV. Higher the transmission voltage means lesser the current and, hence, lesser the I 2R loss. Stepping up the voltage is necessary to increase the transmission efficiency by reducing I 2R losses in the transmission lines.

A step up transformer is used for this purpose, which increases the voltage level with the corresponding decrease in the current. Generation voltage can not be much higher due to technical limitations.įor the transmission of power over longer distances, the generated voltages are stepped up to a much higher level. Electricity is generated in power plants at voltages ranging from 11kV up to 25 kV. A power plant may consist two or more 3-phase alternators which are operated in parallel. There are various types of power generating stations such as thermal, nuclear, hydro, solar, wind etc. Each of these stages is explained in details below.Įlectricity is generated in power plants which are often located far away from the populated areas. The following diagram shows a typical layout of an electrical power grid.Ī power grid can be divided into three stages: Power generation, transmission and distribution. And a distribution system is needed to distribute the power to every consumer at appropriate voltages. Thus, a long distance transmission system is needed to transmit the generated electricity to the populated areas. Also, a hydroelectric plant must be located according to an appropriate dam site or a wind power plant may be located off-shore to harvest additional energy from the wind. This is very practical since the transmission of electrical power over longer distances is a lot much economical than the relative transmission of any other fuel.

Hence, they are often located quite away from the populated areas. Power generating stations are located at feasible places - according to the availability of the fuel, the dam site or an efficient location for renewable sources. A power grid consists of generating stations (power plants), transmission system and distribution system. It is, sometimes, also called as an electrical power system. An electrical power grid is an interconnected network that delivers the generated power to the consumers.

Different types of electrical grids