Karnataka is among the leading states in renewable energy with an installed capacity of over 12 GW, which accounts for nearly half of the state’s total installed power capacity. Of the total renewable capacity, about 5 GW was added in 2017-18. Karnataka Power Transmission Corporation Limited (KPTCL), the state’s transmission utility, has been modernising, upgrading and augmenting its network to support large-scale investments in renewable energy. It is implementing several projects under the Green Energy Corridors (GEC) initiative. Meanwhile, it is implementing a number of technology initiatives to ensure that its network not only has high system availability, but also meets the state’s energy requirements adequately.
Existing infrastructure and performance
In June 2002, KPTCL emerged as the sole transmission company in Karnataka. It is responsible for power transmission in the state, as well as the construction and maintenance of 33 kV and above stations and lines. As of March 2018, the state-owned company owns 1,514 substations – five substations at the 400 kV level, 101 at 220 kV, 413 at 110 kV, 637 at 66 kV and 358 at 33 kV. KPTCL’s network comprises 36,124 ckt. km of transmission lines at the 66 kV and above voltage levels. Its network increased by 3 per cent from 35,119 ckt. km in the previous year. Of the current line length, about 31 per cent is at the 220 kV level, 30 per cent at 66 kV, 29 per cent at 110 kV and 10 per cent is at the 400 kV level.
The utility has also made consistent efforts over the years to reduce its transmission losses, which declined from 4.7 per cent in 2006-07 to 3.22 per cent in 2017-18. The transco’s transmission system availability stood at 99.6 per cent in 2016-17.
Technological advances along with new designs and construction techniques have helped the transco cope with a number of challenges. For instance, to overcome space constraints owing to rapid urbanisation in the state, KPTCL has designed narrow-base towers at different voltage levels to replace the conventional broad-base towers.
Another initiative taken by KPTCL has been to update its design methodology for transmission towers from the old design code IS-802 (1977) to IS-802 (1995). Towers based on the old design were capable of being thermally loaded only up to 75 0C and were based on the older wind zones classification. With the change in standard, the tower’s conductor temperature can be raised up to 85 0C, thus, improving the power handling capacity of the transmission line. Also, now all 220 kV towers have been standardised as per the revised standard.
Further, to address right-of-way (RoW) issues and build transmission lines in forest areas, KPTCL initiated the use of V-string insulators in place of I-string insulators. This has enabled the company to upgrade the existing 110 kV Varahi Shimoga single circuit (SC) line at the Varahi hydel power generating station to a 220 kV double circuit (DC) line keeping the same corridor width of 22 metres.
Another technology that the transco is deploying to optimise space is monopoles. In January 2018, a 220 kV line, passing through an industrial area (Jigani industrial area), was constructed using monopoles, which helped to lay the line in the median of the road with a narrow width (1.5 metres). In addition, KPTCL used single side crossarm towers to avoid cutting of trees on both sides of the line corridor and reduce the RoW to half the recommended width for conventional towers with crossarms on both sides.
New substations based on gas-insulated switchgear (GIS) and hybrid technologies are also being deployed actively. For instance, the transco has undertaken the construction of a 2×500 MVA, 400/220 kV GIS substation at Mylsandra in south Bengaluru; a 2×150 MVA, 220/66 kV GIS substation at Koramangala, ITI and Brindavana in Bengaluru; and a 1×100 MVA, 220/66 kV hybrid substation at Channapatna in Ramanagara district. It has also laid a 220 kV, 2,000 square mm power cable to evacuate power from the 400/220 kV Yelahanka substation in Bengaluru.
Over the next few years, KPTCL aims to install a total of 451 substations – 208 at the 66 kV level, 172 at 110 kV, 58 at 220 kV and 13 at the 400 kV level. The transco also plans to install transmission lines of 15,152 ckt. km with 4,346 ckt. km at 66 kV, 3,496 ckt. km at 110 kV, 4,470 ckt. km at 220 kV and 2,840 ckt. km at 400 kV. The outlay for the projects in 2018-19 is Rs 30,000 million.
Further, to cater to the evacuation needs of the upcoming wind and solar power projects in Karnataka, KPTCL has launched projects, which are currently in the pipeline. Under Phases I and II of the GEC project, KPTCL has planned several line and substation projects in the 400-220 kV range. The company is also planning to deploy new-generation conductors in its network such as high-temperature low-sag (HTLS). The existing 66 kV SC transmission lines in Bengaluru city, which were commissioned nearly four decades ago using ACSR (aluminium conductor steel-reinforced), are now proposed to be replaced with HTLS conductors by KPTCL.
That said, the transco is facing challenges pertaining to RoW and evacuation of the growing renewable energy generation in the state, more so as these projects have a must-run status. The increase in renewable energy penetration and expansion of the transmission network must go hand in hand. Thus, KPTCL’s efforts for scaling up investments in transmission infrastructure can help the state successfully meet its renewable energy goals.