The rising power demand and the increasing share of renewable energy in the power mix are making it increasingly necessary to augment the transmission network in the country. The strengthening of the transmission grid has been at the fore in the recent past, with the government taking critical policy and regulatory measures including providing for ancillary services and establishing a framework for forecasting, scheduling and imbalance handling for variable renewable energy sources. Moreover, technological advances in transmission conductors, towers, substations, etc. are contributing significantly to developing a robust transmission network.
Network size and growth
The power transmission segment saw robust capacity addition in 2015-16, with around 28,114 ckt. km of lines and 62,849 MVA of transformer capacity being added across all voltage levels.
As of May 2016, the total high voltage network comprised 343,033 ckt. km of 220 kV and above lines. Of this, 46 per cent of the network is operational at the 220 kV level, 43 per cent at 440 kV, 7.2 per cent at 756 kV, 2.7 per cent at 500 kV high voltage direct current (HVDC) and 1 per cent at ±800 kV HVDC. During the previous fiscal year, the line length addition was the highest at the 400 kV level.
On the transformer capacity front, as of May 2016, the total capacity stood at 666,884 MVA at 220 kV and above voltage levels. Of this, 44.4 per cent is at 220 kV, 31.8 per cent at 400 kV, 21.6 per cent at 765 kV, 2 per cent at 500 kV HVDC and less than 1 per cent is at the 800 kV HVDC level. During the last fiscal year, capacity addition was the highest at the 220 kV level. Meanwhile, as of April 2016, the total HVDC capacity at converter/back-to-back terminal stations stood at 15,000 MW and the inter-regional power transfer capacity stood at 59,550 MW.
Policy and regulatory developments
During the past year, the government has taken a host of initiatives to promote the development of the transmission network. These have been primarily aimed at expediting the construction time of transmission projects by mitigating the challenges facing developers. In July 2015, the Ministry of Power (MoP) notified the guidelines for the payment of compensation (at the rate of 85 per cent of the land value based on circle or other applicable rates) for right of way (RoW) for transmission lines supported by tower bases of 66 kV and above. Further, compensation of a maximum of 15 per cent of land value will be paid towards the diminution in the width of an RoW corridor due to the laying of a transmission line and the imposition of certain restrictions. The compensation will be decided by the states based on the categorisation of land.
During the same month, the ministry allowed transmission projects to avail of transmission charges from the date of commercial operations, even if a project is ahead of schedule. The move was aimed at incentivising developers to commission transmission projects on time, and thus help reduce congestion in the grid system. Besides this, in December 2015, the MoP waived inter-state transmission charges or losses for renewable energy projects and has urged the states to do the same.
On the regulatory front, there have been significant developments targeting grid stability and security. One of the key developments was the release of the Ancillary Services Operations Regulations, 2015, in August 2015. The regulations aim to restore frequencies in the transmission system to within the prescribed levels, through regulation up or down of select reserves regulation ancillary service providers during periods of low or high frequency, system contingency, etc. Another key regulatory development was the release of the Framework for Fore-casting, Scheduling and Imbalance Handling for Variable Renewable Energy Sources (Wind and Solar) in the same month. The framework aims to ensure grid stability in light of the growing penetration of renewable energy.
As of May 2016, the private sector accounted for 5.9 per cent of transmission line length and 3 per cent of transformer capacity. In the coming years, the role of the private sector in the transmission segment is likely to increase, with a large number of transmission projects likely to be awarded through tariff-based competitive bidding (TBCB). In April 2016, the central government announced that projects worth Rs 300 billion-Rs 500 billion associated with 33 new solar parks will be awarded through TBCB. Earlier, in September 2015, the Central Electricity Authority’s Empowered Committee on Transmission had identified eight transmission projects (Rs 94.68 billion) to be awarded through the TBCB route.
In 2015-16, six projects aggregating Rs 88.7 billion were awarded via the TBCB route – Adani Power Limited secured three projects (Rs 3.6 billion), and Sterlite Grid Limited (Rs 4 billion), Kalpataru Power Transmission Limited (Rs 18.1 billion) and Power Grid Corporation of India (Powergrid) (Rs 63 billion) secured one project each. Despite the government’s intent to increase private sector participation in the segment, the pace of project award through the TBCB route has remained slow. In the past five years, only 22 projects have been awarded through the bidding route. Moreover, the number of bids received for projects put on offer has dwindled over the years – from 12 bidders in 2011 to just four in 2015. Most international bidders are staying away, citing the small project pipeline and concerns about the dominant incumbent as the reasons for doing so. To address these concerns, the government has decided to hive off the central transmission utility function of Powergrid.
Emerging technology trends
There have been significant technological advances in transmission infrastructure to meet the emerging requirements of the segment. The new technologies aim largely at tackling RoW issues as well as lowering network losses. The transmission of power at high voltage levels is gaining prominence in the country, leading to increased power flow per metre of RoW. In September 2015, Powergrid commissioned the first 800 kV HVDC line – the 3,500 ckt. km Biswanath Chariali-Agra bipole line. Besides this, several interregional HVDC links are also under construction, including the ±800 kV, 6,000 MW HVDC terminals associated with the Raigarh (western region)-Pugalur (southern region) bipole link.
On the transmission conductor front, solid conductors have almost entirely been replaced with stranded conductors like aluminium-clad steel-reinforced conductors and all-aluminium conductors. Other technologies that are gaining traction include high temperature, low sag conductors (Odisha Power Transmission Corporation Limited’s 132 kV Indian Charge Chrome Limited Grid-Choudwar line); high surge impedance loading conductors (the 400 kV Meerut-Kaithal double-circuit line) and gas-insulated line conductors (the tunnels set up to evacuate power from the Nathpa Jhakri and Tehri hydroelectric projects). Broadly, these technologies increase the transfer capacity of transmission lines and lower network loss levels.
On the transmission tower front, the design has evolved from conventional lattice-type towers (with a broad base) to compact towers with a narrow base delta configuration. The use of high voltage transmission towers (like 765 kV, 800 kV HVDC and 1,200 kV), delta or vertical configuration towers (compact size), towers with insulated cross arms (reducing both the height and width of the towers), and monopoles (which have a reduced land area requirement) is gaining ground in the country.
On the substation front, the complexity of design has increased over the years owing to growing urbanisation and lack of space. The integration of renewable energy is another challenge. Gas-insulated switchgear substations are increasingly being used in urban areas as these require less land. Besides this, substation automation solutions are also gaining traction. Conventional substations are giving way to digital substations, with copper hardwiring being replaced by digital communication capabilities. The automation of substations allows centralised remote operations and automatic fault analysis, with reduced asset downtime and increased asset life.
Further, new solutions and technologies are being developed in the operations and maintenance (O&M) of transmission assets to maintain equipment in good working condition, ensure zero breakdowns, etc. These include preventive maintenance practices such as transmission line patrolling, ground patrolling, tower top patrolling, aerial patrolling, hotline maintenance and annual maintenance programmes; predictive maintenance or condition monitoring practices like thermovision scanning, punctured insulator detection, pollution measurement, corona scanning, electrical clearance measurement, tower footing resistance measurement and breakdown maintenance. Condition assessment and monitoring techniques are being used to optimise maintenance and reduce system outages. Techniques such as live-line working enable the maintenance of assets without removing them from service.
To conclude, time-bound implementation of projects, reduction in network losses and adoption of advanced technologies are critical to the health of the segment. Moreover, enabling policy and regulatory provisions and an increase in private sector participation are likely to yield positive results in the near future.