• Power systems interconnection in India


    The National Grid is the high-voltage electric power transmission network in mainland India, connecting power stations and major substations and ensuring that electricity generated anywhere in mainland India can be used to satisfy demand elsewhere. The National Grid is owned, operated, and maintained by state-owned Power Grid Corporation of India. It is one of the largest operational synchronous grids in the world.


    Electricity is a concurrent subject in India i.e, both the central and state governments are  responsible  for  the  development  of  the  electricity  sector.  NTPC,  NHPC,  THDC,  NEEPCO,  SJVNL,  NLC  etc.  are  the  central  generation  utilities  and  POWERGRID  is  the  Central  Transmission  Utility.  At  the  State  level,  there  are  Gencos  and  Transco  in  the respective States.   The  country  has  been  demarcated  into  five  electrical  Regions  viz.  Northern  (NR),  Eastern (ER), Western (WR), Southern(SR) and North Eastern (NER).

    Each of the five regions has a Regional Load Dispatch Centre (RLDC), which is the apex body, as per the Electricity Act 2003 (EA 2003), to ensure integrated operation of the power system in the concerned region. The RLDCs for North, East, West, South and Northeast regions are located at Delhi, Kolkata, Mumbai, Bangalore and Shillong respectively.

    The RLDCs coordinate amongst themselves both of line as well as online for maintaining the security and stability of the integrated pan-India grid. In line with the federal structure of governance in the country, every state has a State Load Dispatch Centre (SLDC), which is the apex body to ensure integrated operation of the power system in the state.

    The RLDCs in India are presently owned, managed and operated by the Central Transmission Utility (CTU), POWERGRID while the SLDCs in the state are owned operated and managed by the respective State Transmission Utility (STU) or the State Electricity Board (SEB) as the case may be. The EA 2003 has a provision for a National Load Despatch Centre (NLDC) for optimum scheduling and despatch of electricity across various regions and also coordinating cross border energy exchanges in real time. Ministry of Power has notified the functions of NLDC that is under construction. Presently, POWERGRID is operating a National Power System Desk (NPSD) in New Delhi for information exchange and facilitating interregional transactions. The cross border exchanges are coordinated by the RLDC of the region wherein the international interconnection is situated.

    The backbone transmission system in India is mainly through 400 kV AC network with approximately 1,57,142 circuit kilometers (ckm.(= 2 x route km)) of line length. Highest transmission voltage level is 765kV with line length of approximately 29,950 ckm. There are +/- 500 kV long distance HVDC system with five HVDC Bipole of 12000 MW capacity, an HVDC Monopole of 200 MW, and four HVDC Back-to-Back links of 3000MW capacity. These are supported by about 162530 ckm. of 220kV transmission network. As mentioned above, all the five regions are interconnected through National Grid comprising hybrid AC/HVDC system.

    Conserving Right-of-Way (RoW), minimizing impact on natural resources, coordinated development of cost effective transmission corridor, flexibility in upgradation of transfer capacity of lines matching with power transfer requirement are major areas of concern in development of transmission network in the country. In this direction, the Company has been working on higher transmission voltages of ±800 kV HVDC & 1200 kV UHVAC. 1500 MW (Pole-I) of HVDC terminals at both ends of about 1350 km long ±800 kV, 6000 MW HVDC Bi-pole line connecting Champa in Chhattisgarh to Kurukshetra in Haryana has been commissioned recently. Similarly, power flow through 1200 kV National Test Station (NTS) has commenced at Bina, Madhya Pradesh.

    The high-capacity (800-kV, 6,000-MW) HVDC bipole line is being implemented from Bishwanath Chariali in Assam to Agra in Uttar Pradesh through Alipurduar in West Bengal. The high-voltage corridor would facilitate transfer of 24,000 MW  from future generation projects in the north-eastern region and Bhutan.

    Two more such corridors are likely to come up in India, which include Champa-Kurukshetra (1,350 km) and Raigarh-Pugalur-New Trichur (1,600 km).


    +/- 500 kV HVDC Lines







    HVDC Back-to-back






    HVDC Monopole Line

    Barsur-Lower Sileru