Life assessment and refurbishment of ±500kV, 2500 MW Talcher-Kolar HVDC Converter Stations

The integration of Voltage Source Converter (VSC) technology into the existing Line

Commutated Converter (LCC) system was explored to create a Hybrid HVDC configuration.

However, assessments revealed that the required shutdown duration and implementation timeline were prohibitive. Similarly, while long-standing issues such as ground return mode were addressed, the significant investment required without a corresponding improvement in rating rendered this option unviable. Furthermore, the feasibility of upgrading the continuous power rating from 2000 MW to 2500 MW was examined; however, this major upgrade was found to be techno-commercially unfeasible under current grid conditions.

The service life of the HVDC link can be extended through targeted investment in the replacement of aging equipment. Residual Life Assessment (RLA) served as a primary methodology for defining the refurbishment scope through a condition-based approach. The

RLA concluded that replacing critical components—including control and protection systems, converter valves, smoothing reactors, and converter transformers—is essential to ensuring future reliability and extending the link’s operational life by an additional 15 years. Key drivers for this refurbishment include technological obsolescence, the cessation of Original Equipment

Manufacturer (OEM) support, and historical failure incidents. Specific operational challenges, such as scaling in converter valves and failures in smoothing reactors and converter transformers, were also considered in the finalization of the upgrade plan. This selective component replacement strategy is techno-commercially viable and ensures minimum downtime during implementation.