I S Jha, Chairman & Managing Director, Power Grid Corporation of India explains the need for a strong interconnected national power grid to ensure 24×7 quality power supply and access of electricity to all.
The Indian power system experienced phenomenal growth during the last few decades. Installed capacity has increased significantly from 170 GW during 2010 to 300 GW presently i.e., about 76 per cent increase. Towards this, the private sector has contributed significantly; its share has grown from 29 GW in 2010 to more than 115 GW in 2016, an increase of 296 per cent. In the past five years, penetration of renewable capacity has doubled, i.e., it has increased from 19 GW in 2010 to more than 40 GW in 2016. Peak and energy deficits have significantly come down to less than 2 per cent. Adequate generation and transmission facilities are available to meet the demand. Now the focus is towards ensuring 24×7 quality power supply and access of electricity to all at an affordable price and in an environmental friendly manner.
Energy resources for power generation range from conventional sources like coal, lignite, natural gas, oil, hydro and nuclear power to other viable non-conventional sources like wind, solar, agriculture, domestic waste, etc. Power generation resources, both conventional and non-conventional, are unevenly distributed across the country, usually away from the load centres. Coal is concentrated in the central part of the country, mainly in the states of Bihar, Odisha, Jharkhand, Chhattisgarh and West Bengal. Hydro resources are distributed mainly in the Himalayan range in the Northern and North-Eastern regions. Renewable resources like wind and solar potential are also concentrated in a few states like Tamil Nadu, Andhra Pradesh, Karnataka, Rajasthan, Maharashtra and Gujarat, etc. Transportation of natural resources is costlier, sometimes not feasible (take for example hydro resources), compared to transmitting power to widely spread load centres across the country. Therefore, it requires long haul of bulk power to reach the end consumer. Under these circumstances, transmission acts as an enabler to meet the energy demand from remotely located resources.
Role of Transmission Networks
Transmission is playing a central role towards meeting electricity demand of the country and development of power systems. Today, India has a transmission system made up of about 24,245 circuit kilometre (ckm) of 765kV; 1,47,130 ckm of 400kV and 1,57,238 ckm of 220kV level transmission lines. HVDC bipolar links comprise 12,938 ckm and a massive programme for enhancement of transmission capacity at an estimated investment of about `2,00,000 crore is underway. In addition, there is a massive network of sub-transmission and distribution lines, supplying power to end consumers. Such a large interconnected, 3,41,550 ckm-long robust transmission network has facilitated seamless flow of power across the length and breadth of the country.
The past five years have seen phenomenal growth in the development of the transmission system network in the country. National grid capacity has been strengthened significantly through large-scale addition of 765 kV Extra High Voltage (EHV) transmission network. About 24,000 ckm of 765kV lines and more than 40 numbers of 765 kV substations have been added in the past five years. More than 40,000 ckm of 400 kV lines have also been added in the past five years. The major challenge in the development of the transmission system is the availability of Right of Way (RoW) for transmission lines and acquisition of land for establishment of substations.
Towards establishment of an efficient, reliable and secure transmission system in the country, while addressing RoW & land acquisition issues, latest technologies viz., HVDC systems, GIS substations, FACTS devices like STATCOM, SVC etc., are being adopted on a large scale. FACTS devices are installed in important AC transmission lines to increase the power transfer capacity. The hybrid mix of AC and DC transmission system in India has helped the system operator to exercise a better control over the grid and has also imparted flexibility in operations during any exigencies. The HVDC interconnection (along with AC tie-lines) between the regional grids helps to control the power flow on the AC tie-lines. The HVDC Back-to-Back and Long Distance HVDC interconnection along with AC tie-lines between the regional grid helps to control the AC tie-line flows.
On the technology front, India has emerged as a pioneer and is a world leader with the commissioning of 1,800 km of Â±800 kV multi-terminal HVDC system from Biswanath Chariali in the North-Eastern region to Agra in the Northern-Region (See Figure-1) and successful indigenous development of the 1200 kV UHV AC system (highest voltage in the world) which is under field trial since the past two to three years (See Figure-2).
After de-licensing of generation in the Electricity Act 2003, Independent Power Producers (IPPs) have been coming up in resource-rich and coastal states such as Chhattisgarh, Odisha, Madhya Pradesh, Sikkim, Jharkhand, Tamil Nadu and Andhra Pradesh. To cater to Bulk Power Transfer requirements, 11 High Capacity Power Transmission Corridors (HCPTCs) are being implemented in a phased manner matching with generation projects.
One Nation – One Grid
In the journey towards seamless flow of power across the region, on 31st December 2013, the Indian power sector achieved a major milestone when the Southern Regional Grid was successfully synchronised with the Â´NEWÂ´ grid (North, North-East, East & West grids) through the 765 kV Raichur-Solapur line. With this milestone, the country now has only one synchronously connected grid in operation and the long cherished dream of Â´One Nation-One GridÂ´ has been fulfilled. Starting from five regional grids in the early nineties, we have today one national grid comprising more than 53,150 MW of inter-regional capacity that would increase to 72,250MW by the end of the 13th Plan period. Evolution of the National Grid from the regional grid is depicted in Figure 3.
At present, the National Grid is one of the largest in the world, with installed capacity of about 300 GW and meeting a peak demand of more than 150 GW.
By adopting world class operation and maintenance practices and a state-of-the-art monitoring and control system at Load Dispatch Centres (RLDCs/NLDC) and the National Transmission Asset Management Centre (NTAMC), the National Grid system is being maintained at high availability (more than 99 per cent) ensuring compliance with prescribed standards for uninterrupted supply of power to customers. For dynamic stability monitoring & control, enhanced situational awareness etc., Load Dispatch Centres are equipped with the synchrophasor measurement system. Under this Wide Area Measurement scheme about 63 Phasor Measurement Units (PMUs) have been installed at strategically selected locations across the country as a pilot project. The worldÂ´s largest deployment of more than 1,700 PMUs at all inter-state and intra-state extra high voltage substations (400kV & above) has been undertaken as the Unified Real Time Dynamic State Measurement System (URTDSM) project. Process Bus technology is being adopted at the substation to make it more efficient. Hot line maintenance, helicopter-based aerial patrolling using high-resolution cameras, condition monitoring of equipment, etc., have been adopted to ensure better reliability and availability of the transmission system.
Benefits of National Grid
The robust network of transmission system in the country has facilitated in harnessing the opportunities due to various types of diversity with respect to electricity production and consumption.
Because of its vast geographical spread, India has time diversity of peak demand i.e., peak hour occurs early in the eastern & north-eastern parts of the country compared to the western parts. With the strong interconnection among regions, the same power plant can supply demand at different times in different regions. It has helped in improving the utilisation of existing resources, improved Plant Load Factor (PLF) of thermal power plants (Figure 4), enhanced the frequency profile of the interconnected system, and improved inertia of the system. The strong and highly integrated transmission system has enabled development of a vibrant electricity market resulting in fall of electricity price from more than Rs 8 per unit in 2004 to less than Rs 3 per unit at present in power exchanges and provided momentum to the growth of the power sector as a whole. (Refer to Figure 5).
Further, for the first time, the spot market price of electricity on 29th December 2015 was at a single price, i.e., Rs.2.30 throughout the country, a great achievement for the power sector. Thereafter, on several occasion, a single price has been witnessed in the power exchanges across the country.
Information about the availability of power in the different parts of the country can be directly seen on the recently launched web portal http://vidyutpravah.in/ by the Ministry of Power (See Figure 6). It can be seen that stable and reliable transmission infrastructure of the country has brought competition in the sector, providing electricity at affordable price and also has brought efficiency into the sector. It has also facilitated integration of renewable generation by increasing the grid size, to smoothly absorb variability and uncertainty associated with it.
Renewable energy development is being taken up on a big scale to meet the multiple objectives of energy security and development of clean energy for sustainable development. In the past one decade, renewable energy penetration has increased from merely 2.5 GW in 2005 to about 40 GW in 2016. In this context, the government has set an ambitious target of 175 GW of renewable generation by 2022, which includes 100 GW of solar, 60 GW of wind and 15 MW of other renewable forms of energy. Out of the 100 GW solar generation, 20 GW will be through solar parks, 40 GW through distributed solar generation and the remaining 40 GW would be through rooftop solar generation. The government has identified 34 solar parks in 21 states, and EHV transmission system for evacuation of bulk power from these solar parks is also being developed in the form of inter-state/intra-state transmission schemes. Renewable generation is highly intermittent, variable and uncertain in nature. The strongly interconnected transmission system present in India has played a vital role in integration of such a large scale of renewable generation. The system helps in transfer of power from surplus regions to deficit regions and helps in sharing of resources for dealing with intermittency and variability of renewable generation. To further facilitate the integration of upcoming large scale renewable generation, Green Energy Corridors are being developed, that include the inter-state transmission system as well as intra-state transmission system.
This exercise also includes establishment of a Renewable Energy Management Centre for forecasting and scheduling of RE generation, dynamic compensation, load balancing, ramping, demand response, grid-scale energy storage, etc. There is no single technology or design, but this is a general term for the transformation of the power grid using digital communications and control to enable functionalities such as increased monitoring, resiliency, flexibility, efficiency, and intelligence.
With large scale integration of renewable generation, de-licensing of generation and a growing electricity market, there is a paradigm shift in the way the power system is being operated and maintained at present. On the one hand, to bring efficiency into the sector, various components of the power supply value chain are being operated at their limits and on the other hand, the consumer demands reliable supply. In this context, a strong interconnected Â´One Nation, One GridÂ´ spread over large geographical areas of non-uniformly distributed resources plays a vital role in facilitating transfer of bulk power from remotely located generating stations to load centres. Strengthening of inter-regional tie-lines among various regions has immensely helped all sectors in the power supply value chain. The PLF of power plants has improved, availability of supply to end consumers has improved and network stability has improved, because of enhanced inertia and better resource management (energy balance).
After achieving the target of One Nation-One Grid, efforts are now being made to further strengthen the National Grid, so that there is no bottleneck in the seamless flow of power across the country and we can have Â´One Nation-One Grid-One PriceÂ´ in the country soon.