Power transmission service providers have identified high wind speeds caused by climate change events as one of the main reasons for recurring transmission tower failures in India.

In all, there were 76 extra-high-voltage (EHV) transmission line tower failures across 28 transmission lines, including 220 kV, 400 kV, and 765 kV AC lines, in 2024, as reported by 12 public and private power utilities, such as Power Grid Corporation of India, NTPC, and Adani Transmission.

EHV and ultra-high voltage (UHV) lines are crucial for the evacuation of renewable energy over long distances and across states. The Ministry of Power recently announced that the power transmission infrastructure is being enhanced with a UHV alternating current transmission system. As part of this ₹530 billion (~$6.2 billion) initiative, nine 1,100 kV lines and ten substations have been identified for development by 2034.

India aims to expand its power transmission network to 648,000 ckm by 2032, up from 485,000 ckm in 2024, to meet a peak electricity demand of 458 GW.

A report by an expert committee set up by the Central Electricity Authority on EHV transmission tower failures stated that while high-intensity winds have been blamed, utilities often failed to provide wind data in many cases, which could help substantiate their reasoning.

The committee said, “The 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.” It observed that the utilities must obtain the wind data for the area from the Indian Meteorological Department (IMD) or nearby airports, which would serve as a representative wind speed prevailing in that area at the time of failure.

The utilities and the committee agreed that the high wind velocity during storms and whirlwinds might have exceeded the design wind speed for which the towers were designed.

The experts’ committee asked the utilities to seek IMD’s help and utilize wind-related data from wind sensors to analyze their respective tower failure events.

India’s wind map was previously divided into three wind pressure zones: light, medium, and heavy, before the revision of IS 802 in 1995. In the third revision of IS 802: 1995, six wind zones were specified, dividing various regions based on the three-second wind gust speed.

The committee observed that most tower failure incidents occurred on transmission lines designed for wind zones 2 and 4, which cover the largest areas of India.

The IMD informed the committee that it had already established a network of wind sensors at approximately 700 locations, each capable of capturing related wind parameters, including speed, within a 10 km radius.

Besides the IMD, agriculture and irrigation departments in some states have also installed a network of wind sensors to capture weather-related information, including wind speeds.

The committee noted that the wind map was last revised by the Structural Engineering Research Centre in 2016, using 2009 wind data, and was subsequently incorporated into the National Building Code by the Bureau of Indian Standards. However, the revised wind map is yet to be included in the latest building code.

Besides high wind speeds, thefts, sabotage, and right-of-way encroachments were also listed as reasons for transmission tower failures. In one case, an explosion caused by an improvised explosive device damaged two legs of the tower in the 400 kV D/C Silchar-Imphal Line.