System interconnection(Lines)

Two or more generating stations are interconnected by tie lines.Interconnection of generating stations has the following important advantages:

1.It enables the mutual transfer of energy from surplus zone to deficit zone economically.

2.Lesser overall installed capacity to meet the peak demand.

3.Lesser standby reserve generating capacity.

4.The size of the biggest unit is not related to the peak load of an individual system but it related to the peak load of the interconnected system.Thus,fewer but larger machines of greater efficiency are to be installed.

5.It permits the generation of energy at the most efficient and cheapest stations at every time.

6.It reduces the capital cost,operating cost of energy generated.

7.If there is a major breakdown of a generating system unit in an interconnected system there is no interruption of power supply.Similarly,when a machine is taken out of service for its scheduled maintenance and inspection,the continuity of supply is maintained.In other words,the planning of plant outages for maintenance and repair work is facilitated.

Thus,interconnection provides the best use of power resources and ensure greater security of supply.It enables overall economic generation by optimum use of high capacity economical generating plants.Interconnection between network is done either by  HVAC links or HVDC links.

An interconnected power system covering a major portion of a county's territory(or state) is called a grid.The different grids may be interconnected through transmission lines(called tie lines) to form a regional gird.When the different regional grids are interconnected,they form a national grid.