India records 75 EHV transmission tower failures in six months

Between January 1 and June 30, 2025, eleven utilities reported 22 cases of extra-high voltage (EHV) transmission line failures to the Standing Committee of Experts constituted by the Central Electricity Authority (CEA). These incidents involved a total of 75 towers, of which 59 were suspension-type and 16 were tension-type. Among the tension-type towers, eight were classified as “Type B,” two as “Type C,” and six as “Type D.” The committee’s scope covers EHV transmission lines of 220 kV and above.

Analysis of the 2025 data shows that suspension-type towers were more frequently affected than tension-type towers. This pattern reflects both their greater numbers along most transmission lines and their structural design, which prioritises vertical load support over horizontal or longitudinal forces. Consequently, the failure of one suspension tower can lead to secondary collapses in nearby towers due to conductor forces. The revised IS 802:2015 standard now specifies stricter loading criteria for suspension towers, including longitudinal and transverse forces under security conditions.

The committee also noted delays in reporting failures. Some utilities did not notify incidents within 48 hours or submit detailed reports within one month, which limits timely analysis. Another concern is that several failures occurred earlier than expected. Of the 22 incidents in the first half of 2025, 16 involved towers in service for only 10 to 15 years, while the design life is typically 35 years. Comparatively, the 75 tower failures in these six months are nearly equivalent to the total of 76 failures reported for all of 2024, suggesting a similar rate rather than a significant increase.

The report identified several types of tower failures, including deformation of legs or cross-arm structures, buckling at stub or panel levels, collapse with or without foundation damage, foundation damage due to water flow or soil erosion, and shearing of stub members. Utilities commonly cited high winds, cyclones, or heavy rainfall as causes. The committee recommended that tower design consider terrain type, local wind conditions, and areas prone to high winds, and that utilities support wind-related claims with data. In-house teams with design software were advised to simulate and analyze failed towers for better assessment and mitigation.

The 11 reporting utilities included PGCIL, RVPNL, THDCIL, GETCO, MPPTCL, UPPTCL, Renew, KPTCL, NTPC, NRSS XXXVI, and AESL. The 22 affected lines comprised one 765 kV line, twelve 400 kV lines, and nine 220 kV lines, with the sole 765 kV line being PGCIL’s Fatehpur-Agra 2 line in Uttar Pradesh.

Coordination with the Indian Meteorological Department (IMD) and other agencies was emphasised. IMD has a network of wind sensors at approximately 700 locations, capturing wind parameters within a 10 km radius. Utilities were advised to coordinate with IMD, the Airports Authority of India, nearby wind farms, and state irrigation departments to obtain wind data at failure sites. Replacement towers and spares should comply with prevailing regulations, applicable standards, and local wind conditions.

Cumulative data from the Standing Committee since its reconstitution in 2012 shows that, up to June 30, 2025, 964 cases of EHV transmission tower failures have been reported across India, providing a historical perspective for monitoring trends and identifying recurring issues.

Alongside tower failures, the committee reviewed 17 transformer and reactor incidents from the same period. Eleven occurred at 400 kV and six at 220 kV, with no incidents reported at 765 kV. Failures included early-life cases, with six transformers failing within five years of service. Key factors were aging of insulation and bushings, lightning or insulation faults, maintenance gaps, and repeated system stresses.

Examples include GETCO’s Kasor 100 MVA transformer, which failed due to a short underground cable fault, NTPC’s Singrauli transformer, commissioned in 1982, which experienced insulation degradation, and PSTCL’s Moga transformer, affected by lightning and frequent system faults.

Recommendations for transformers included dynamic short-circuit withstand testing, adoption of condition-based maintenance using modern diagnostics such as SFRA, DGA, and bushing oil tests, comprehensive reporting covering pre-commissioning, factory tests, operational history, and post-failure analysis, and centralized monitoring for real-time asset health. Environmental protection measures such as RTV coatings in dusty locations and ongoing engagement with OEMs for design feedback were advised, along with attention to staffing and timely commissioning of equipment.

The findings highlight the need for ongoing improvements in tower and transformer design, monitoring, and maintenance, especially in areas exposed to high wind or environmental stress. Adoption of the committee’s recommendations is intended to support consistent operational practices and reduce the risk of future failures.

The featured photograph is for representation only.