Primary distribution lines contain a distribution transformer present in the locality of the clientele. Primary distribution ranges from 4 to 35-kilo Voltage. Only industries can directly feed the transmission line. Most average consumers are connected to a transformer that brings down the voltage to a useable level. The distribution network for the primary distribution comes in three types, although they are mainly of two types—radial or network. A radial network is primarily like a tree, where there is only one line of connection for the customer to the source of supply. A network system, on the other hand, has multiple or parallel connections to the source of supply. A radial connection is primarily used in rural areas, while the network connection is primarily used in load-sensitive areas, such as a dense urban area. However, as bad as radial systems sound, based on there only being a single connection to the source, modern-day radial networks do contain backup options.
The parameters that encompass the properties of electricity are not strictly limited to voltage and current. When it comes to electricity, there is a third important property of electricity—frequency. There are primarily two frequencies in which electricity is produced, either 50 or 60 Hz. This electricity is then delivered to domestic customers as single-phase electric power.The domestic power supply in North America would look like a sine wave, oscillating between −170 volts and +170 volts, giving an effective voltage of 120 volts RMS.
However, in some countries of Europe and India, three-phase power is more efficient in terms of power delivered per cable used and is more suited to running large electric motors. Some large European appliances may be powered by three-phase power, such as electric stoves and clothes dryers. A ground connection is normally provided for the customer’s system, as well as for the equipment owned by the utility. The purpose of connecting the customer’s system to the ground is to limit the voltage that may develop if high voltage conductors fall onto lower-voltage conductors, which are usually mounted lower to the ground, or if a failure occurs within a distribution transformer; this process is also famously known as grounding.
The Indian Power system for planning and operational purposes is divided into five regional grids. The integration of regional grids, and thereby establishment of National Grid, was conceptualised in early nineties. The integration of regional grids which began with asynchronous HVDC back-to-back inter-regional links facilitating limited exchange of regulated power was subsequently graduated to high capacity synchronous links between the regions.
The initial inter-regional links were planned for exchange of operational surpluses amongst the regions. However, later on when the planning philosophy had graduated from Regional self-sufficiency to National basis, the Inter-regional links were planned associated with the generation projects that had beneficiaries across the regional boundaries.
By the end of 12th plan the country has total inter-regional transmission capacity of about 75,050 MW which is expected to be enhanced to about 1,18,050 MW at the end of XIII plan.
Synchronisation of all regional grids will help in optimal utilization of scarce natural resources by transfer of Power from Resource centric regions to Load centric regions. Further, this shall pave way for establishment of vibrant Electricity market facilitating trading of power across regions. One Nation One Grid shall synchronously connect all the regional grids and there will be one national frequency.
Evolution of National Grid
- Grid management on regional basis started in sixties.
- Initially, State grids were inter-connected to form regional grid and India was demarcated into 5 regions namely Northern, Eastern, Western, North Eastern and Southern region.
- In October 1991 North Eastern and Eastern grids were connected.
- In March 2003 WR and ER-NER were interconnected .
- August 2006 North and East grids were interconnected thereby 4 regional grids Northern, Eastern, Western and North Eastern grids are synchronously connected forming central grid operating at one frequency.
- On 31st December 2013, Southern Region was connected to Central Grid in Synchronous mode with the commissioning of 765kV Raichur-Solapur Transmission line thereby achieving ‘ONE NATION’-‘ONE GRID’-‘ONE FREQUENCY’.
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