Nearly 70 years ago, the power system in India consisted of small isolated generating plants catering the local electrical needs. The post independence era witnessed a significant growth in the power sector. To enhance the reliability of power supply and for achieving economical operation, interconnection of individual systems was planned which led to the formation of state electricity grid in 1950s.
By the sixties, the management of power grid started on regional basis. The state owned power grids were interconnected to form regional grid. With the goal to rapidly develop India at the power sector front, the country was divided into 5 power regions viz. Northern, Western, Southern, Eastern and the North-Eastern power region. Also by mid 60s, Regional Electricity Boards came into existence in the above mentioned five power regions. The move has facilitated interconnected operation of the power system within the regions. The basic role of these regional electricity grids was planning and operation of electric power system within their region.
Now the job was to integrate these regional grids. The basic theme was the formation of a synchronously connected national grid. Things started in 1990 with the asynchronous interconnection between regional power grids made with the help of back-to-back High Voltage Direct Current (HVDC) links such as the Vindhyachal link. Later on other HVDC links also came up such as the Chandrapur and Vishakapatnam-Gazuwaka HVDC links. These HVDC links had limited capacity for exchange of power.
The first move towards achieving the “one nation, one grid, one frequency” status, was the interconnection of North-Eastern and the Eastern grid in 1991. Next was the interconnection of Western grid with the Eastern and North-Eastern grid in 2003. Similarly in 2006 the Northern grid was interconnected with the above three grids. The four regional grids i.e. Eastern, North-Eastern, Western and Northern collectively formed the Central Grid operating synchronously at one frequency. Initially these inter-regional transmission links carried the operational surplus energy from the energy sufficient region to the energy deficient region. Later on the inter-regional transmission links were planned considering the generation plants having beneficiaries spread over the nation.
On December 2013, months ahead of the schedule, the Southern grid too was synchronously connected to the rest or the Central grid through the 765 kV Raichur-Solapur transmission network. With this the mission “one nation, one grid and one frequency” was accomplished.
Interconnected power system and formation of one national grid will reduce the investments in generation reserves, and helps to utilize the benefits of generation mixes and load pattern to a greater extent. This will also facilitate the smooth and efficient operation of the Indian electricity market. For example, till now there was a large inconsistency in the short-term electricity prices in the southern region and the other region because of the inadequate transmission capacity.
Now all the regional grids were synchronized but still the power transfer capability of the national grid was low considering the giant size of the Indian power system. At the end of the 11th Five Year Plan (FYP) the total inter-regional power transfer capacity through inter-regional transmission link was about 28 GW. This inter-regional capacity is expected to reach 65 GW by the end of 2017. So we have completed the “one nation, one grid, one frequency” challenge, but to make this unified grid of significant size having a matching transfer capability and its efficient operation is a bigger one.