A committee of experts, led by the Central Electricity Authority (CEA), tasked to investigate failure incidents of extra heavy voltage (EHV) transmission towers in 2024, attributed the same to high intensity winds due to changing climatic patterns.
All utilities are mandated to report failure of 220 kilovolt (kV) and above voltage class transmission line towers within 48 hours and submit a detailed report to the CEA on the reasons for failure and measures taken to avoid recurrence.
This Standing Committee of Experts reviews the design and operation of EHV transmission lines. They are drawn from the CEA, Central Power Research Institute (CPRI), transmission utilities and research/ academic institutes.
Transmission towers
The committee’s chair expressed concern that many utilities are not intimating failure cases within 48 hours, and are failing to submit detailed failure reports within one month. He also raised concern over non-participation of utilities that reported failure incidences in the meeting.
Of the 12 utilities that reported failures, representatives from just eight utilities attended the meeting. Representatives from Transmission Corporation of Andhra Pradesh (APTRANSCO), Maharashtra State Electricity Transmission Company (MSETCL), Gujarat Energy Transmission Corporation (GETCO), and NTPC did not attend.
Member Secretary said that a total of 28 incidents of failure of EHV transmission line towers were reported to the CEA in 2024 by 12 Utilities (PGCIL, ADANI, RVPN, MSPCL, APTRANSCO, MSETCL, HVPNL, GETCO, MPPTCL, DTL, DVC, and NTPC).
It included 68 suspension-type towers and eight tension-type towers. The failure of 10 transmission lines of four utilities was intimated within 48 hours, and a detailed failure report of only 14 transmission lines of eight utilities was submitted within a month.
The panel is of the view that wind plays an important factor in the design of transmission towers. Hence, obtaining accurate wind speed data relevant to tower failure incidents would be helpful in verifying the effectiveness of tower design, and enable utilities to improve the same.
Climate change
The main cause of tower failures is attributed to high-intensity wind as reported by the transmission utilities; however, the utilities failed to produce wind data in many cases of EHV transmission line tower failures, which could substantiate their reasoning, the panel said.
Transmission utilities are unable to produce the actual wind speed data on the day of failures due to non-availability of wind speed data at the failure location.
The panel also observed that wherever reporting of tower failure is due to wind, the utility needs to get wind data for the area from the IMD observatory/ nearby Airport, which would serve as representative wind speed prevailing in that area at the time of failure.
The panel deliberated on ways and means of obtaining wind speed data relating to tower failures, as it would be helpful in verifying the effectiveness of the tower design.
It agreed that high wind velocity during storms and local conditions of whirlwind might have exceeded the design wind speed for which the tower is designed. However this needs to be verified.
Wind sensor
A previous proposal of installing wind sensors at appropriate locations was discussed. It was suggested to go for the same on pilot basis, with the help of India Meteorological Department (IMD).
The IMD representative emphasised on the importance of capturing accurate and comprehensive wind data for better understanding and assessment of localised storm phenomena and whirlwinds.
He also highlighted that if additional wind data could be collected from interior tower locations operated by various power utilities, it would significantly enhance the ability to analyse wind patterns.
The committee pointed out that the wind map was last revised by SERC in 2016 using the 2009 wind data. However, the revised wind map is yet to be included. The current wind patterns prevailing over various areas have changed in the past few years due to various reasons including climate change events, and there is a need to revise the wind zone map of India prepared by SERC, and incorporated in NBC in 2016.