Summary
India’s national transmission system functions as a single unified grid formed by the synchronisation of five regional networks. In the Northern Region, several 400 kV substations built during the 1990s—originally designed for much lower fault levels—have become part of an expanded and stronger 220 kV and 765 kV transmission network. Rapid load growth and significant additions in Extra High Voltage (EHV) transmission and generation have reduced system impedance, causing short-circuit levels to rise beyond the design capability of older switchgear, creating risks of overstressing and equipment failure.To control these elevated fault currents, multiple mitigation options were studied, including bus splitting, replacement of existing switchgear, and installation of series current-limiting reactors. After evaluating reliability, implementation time, and operational flexibility, The transmission system operator(TSO) selected series reactors as the most suitable solution. Bus and line series reactors were commissioned during 2018–2019 at the Mandola and Ballabgarh substations.As this was
Read more Read lessTSO’s first implementation of fault-current-limiting reactors, challenges emerged in design, procurement, installation, and protection coordination. Additional operational aspects—such as thermal performance, harmonics, and integration with existing protection systems—required careful analysis and refinement.
This paper presents a detailed assessment of the application of series reactors for fault level mitigation in ageing TSO substations and documents the comprehensive operational experience gained since their commissioning. The study highlights several key technical challenges observed during real-time operation, including the mitigation of nuisance tripping associated with series reactors, necessary revisions in distance and differential protection settings, and the impact of altered current paths on relay sensitivity and coordination. Additionally, operational observations related to mechanical integrity—such as vibration under high-load conditions, and long-term insulation ageing—are critically examined to evaluate equipment robustness and reliability.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | A3_10260_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | India |
| Study committees | |
| File size | 890 KB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
BHAKAL* Ramjash - POWERGRID , India; JHA Pankaj Kumar - POWERGRID , India; SINGH Vineet Kumar - POWERGRID , India; SAHU Kuleshwar - POWERGRID , India
Keywords
Operational, experience, reactors, conventional, substation, Indian grid
