Electricity Transmission and Distribution
Electric power transmission is the process in the transfer of electrical power to consumers and refers to the 'bulk' transfer of electrical power from one location to another. Transfer of electrical power from Generating Stations to the industrial, commercial or residential consumers is as important as power generation. Typically power transmission is between the power plant and a substation in the vicinity of a populated area. To satisfy various instantaneous demands from consumers requires an uninterrupted flow of electricity. In the energy delivery industry, the transmission system functions in much the same way as the interstate highway system, serving as its major transport arteries. A power transmission system is sometimes referred to as a "grid", which is a fully connected network of transmission lines. The Regional Power Grids are established for optimal utilisation of the power generated from the unevenly distributed power generating stations, by having intra-regional and inter-regional power exchanges depending upon day-to-day power availability and load conditions. The surplus power is transferred to the power deficit regions. Due to the large amount of electric power involved, transmission normally takes place at high voltage (110 kV or above). Electric power is usually sent over long distances through overhead power transmission lines. Power is transmitted underground in densely populated areas, such as large cities, but is typically avoided due to the high capacitive and resistive losses incurred. Redundant paths and lines are provided so that power can be routed from any power plant to any load center, through a variety of routes, based on the economics of the transmission path and the cost of power. The grid consists of two infrastructures: the high-voltage transmission systems, which carry electricity from the power plants and transmit it hundreds of miles away, and the lower-voltage distribution systems, which draw electricity from the transmission lines and distribute it to individual customers. High voltage is used for transmission lines to minimize electrical losses; however, high voltage is impractical for distribution lines. Electricity distribution is the penultimate process in the delivery of electric power, i.e. the part between transmission and user purchase from an electricity retailer. It is generally considered to include medium-voltage (less than 50kV) power lines, low-voltage electrical substations and pole-mounted transformers, low-voltage (less than 1000V) distribution wiring and sometimes electricity meters. This interface features transformers that "step down" the transmission voltages to lower voltages for the distribution systems. Transformers located along the distribution lines further step down the voltage for household use. Substations also include electrical switchgear and circuit breakers to protect the transformers and the transmission system from electrical failures on the distribution lines. Circuit breakers are also located along the distribution lines to locally isolate electrical problems (such as short circuits caused by downed power lines).
Captive Power Generation
The industrial sector is the largest consumer of electricity. Besides purchasing power from the utilities, a number of industries, viz. aluminium, cement, fertilizer, iron, steel, paper, sugar etc. have their own captive power plants either to supplement the electricity supply from the utilities or for generating electricity as a by-product through co-generation. Captive power plants can be set up by industries to meet their own power requirements to enable them to tide over problems due to power shortages and poor quality of supply. They can use any easily available fuel - coal, gas, diesel, fuel oil - or any other conventional or non-conventional so long as they are able to generate stable power for their requirements all through the year without any interruption.