At the time of Independence, the power system in India consisted of small isolated power generating plants catering the electrical needs of major cities and towns. The total installed capacity at that time was merely 1300 MW and the highest transmission voltage was 132 kV AC. The post independence era witnessed an appreciable growth in the power sector.
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. Interconnected power system reduces the investments in generation reserves, and helps to utilize the benefits of generation mixes and load pattern to a greater extent. The transmission voltage had increased to 400 kV AC by the 70s. Significant transmission networks were developed by Uttar Pradesh, Maharashtra, Madhya Pradesh, Gujarat, Orissa, Andhra Pradesh and Karnataka as these states were having the bulk of the electrical load.
In the year 1975, to enhance the generation capacity, which till the time was carried out at the state level, Central sector generation utilities i.e. National Hydroelectric Power Corporation (NHPC) and National Thermal Power Corporation (NTPC) were formed. These corporations established generating power plants of large capacity, say of 1000 MW capacity, and developed the much needed transmission systems. To speed up the transmission infrastructure development, Power Grid Corporation of India (POWERGRID) was created in 1989.
Till the time all the 5 power regions were operated independently and that too at different operating frequency. Therefore in 1990 asynchronous interconnection between regional power grids were made with the help of back-to-back HVDC links. This was the introduction of HVDC system in the country. In the year 2007, India touched the 765 kV AC transmission voltage and by 2009 we had a couple of ± 500 kV bipolar HVDC lines.
Fig: Under construction 765 kV lines in Madhya Pradesh
Shortly (by 2015) we are going to have the first multi-terminal UHV DC system. The ±800 kV, 1728 km long Biswanath- Agra UHV DC transmission system with a 8 GW converter capacity, including a 2 GW redundancy, will transmit hydroelectric power from the country’s northeast region to Agra in Uttar Pradesh.
In the next decade 1200 kV UHV AC system is expected to emerge as the main transmission level in India along with the 800 kV UHV DC system. The power transfer capacity of 1200 kV UHV AC transmission system is expected to be between 6000 to 8000 MW. To develop 1200 kV AC transmission system in India, a joint venture for a test sub station and test line by Power Grid Corp. of India and CPRI is under progress at Bina in Madhya Pradesh.
Watch out for development of national grid in the coming blog.