The Standing Committee of Experts, constituted by the Central Electricity Authority (CEA), has issued a report revealing a number of failures in 220 kV and above voltage class substation equipment across India between July 2023 and December 2024. The committee has investigated these failures and has recommended measures to prevent their recurrence.
The report, prepared based on data provided by 26 power utilities and deliberations held on March 24 and 25, 2025, in New Delhi, highlights a total of 162 failure incidents involving various crucial substation components. These include Transformers, Reactors, Instrument Transformers, Surge Arresters, Circuit Breakers, Disconnectors, Wave Traps, Coupling Capacitors, Bays, Cables, and PASS Modules.
Key Findings from the Report
36 transformer failures were reported, with 12 being 400 kV class and 24 being 220 kV class. Notably, no failures were reported in the 765 kV class.
Current Transformers saw a high number of failures, with 42 incidents reported (34 of 220 kV, 5 of 400 kV, and 3 of 765 kV class).
There were 42 reported failures of Surge Arresters, predominantly in the 220 kV class (35 incidents).
The analysis of the failed equipment’s operational lifespan revealed that 22 units failed within five years, 38 failed between 5-10 years, 66 failed between 10-20 years, and 31 units had been in operation for over 20 years. Commissioning dates were not provided for five pieces of equipment.
Recommendations for Prevention
The Standing Committee has put forth several key recommendations to mitigate future equipment failures, particularly for Transformers and Reactors:
- Utilities are urged to adopt Condition Based Monitoring practices utilizing modern online diagnostic tools to assess the health of critical equipment.
- For Transformers and Reactors nearing their service life, intensified monitoring with adjusted measurement frequencies based on their condition is crucial. Trend analysis of test results is emphasized over reliance on absolute values.
- Frequent cleaning of dust accumulation on the housings of major equipment and transformer bushings is essential, especially in thermal power plants and heavily polluted areas, to prevent flashovers that can lead to failures.
- The implementation of a centralized electrical asset monitoring system is recommended to track the condition of medium and high voltage assets, including GIS, AIS, breakers, power cables, and transformers. This system should store all Factory Acceptance Test (FAT), Site Acceptance Test (SAT), and periodic testing data for health assessment, incorporate advanced health index models based on IEEE, IEC, and CIGRE standards, and integrate online monitoring data from sensors and visual inspection reports. The system should support parameters like DGA, Partial Discharge, bushing monitoring, and fan control, with accessibility across various devices.
- Regular monitoring of the 3rd harmonic resistive component of leakage current for Surge Arresters and Dynamic Contact Resistance Measurement (DCRM) tests for Circuit Breakers every two years are advised.
- Utilities are strongly encouraged to align their operation and maintenance practices with the model O&M guidelines issued by the CEA.
This report underscores the importance of proactive maintenance and the adoption of advanced monitoring technologies to ensure the reliability and longevity of critical substation equipment, ultimately contributing to a stable and efficient power supply across the nation.
