From Dormancy to Operation: Successful Restoration, Installation and Commissioning of a 420kV Gas Insulated Switchgear (GIS) After Prolonged and Adverse Storage

GIS technology is widely used in hydroelectric power plants, especially in mountainous regions where flat land availability is scarce. In such environments, GIS plays a critical role in switching operations power evacuation system, typically at 220kV or 400kV level in India.

The project involved a large-scale hydroelectric installation where the GIS system— comprising 18 circuit breaker bays—was essential for operational readiness. The bays included 8 generator unit bays, 6 transmission line bays, 2 auxiliary transformer bays, and 2 bus coupler bays, configured in a double busbar arrangement with bus sectionalizer to enhance reliability and short-circuit resilience.

The equipment had been stored in a high-rainfall zone for a decade, leading to moisture ingress, corrosion, and mechanical degradation, particularly in spring-operated mechanisms.

Initial assessments raised concerns about the feasibility of using the long-supplied equipment, especially since the Original Equipment Manufacturer (OEM) had no prior experience of erection and commissioning of GIS systems of such old supply in their portfolio and was very apprehensive regarding the feasibility of its successful erection and commissioning.

Nevertheless, a comprehensive evaluation was carried out first at the site and then of critical equipment at GIS factory in India, wherein a dedicated test bed was developed specifically for this project.

A strategic restoration plan was implemented, involving factory-level repairs/testing of critical components such as circuit breaker poles, operating mechanisms, and surge arresters.

All consumables required for erection, including gaskets and O-rings, were freshly supplied.

The Gas Monitoring System was also redesigned using modern sensors without altering the core equipment. Local control cubicles were refurbished or replaced, and damaged erection tools were replenished. Special infrastructure, including a high-voltage test bed, was developed to support the restoration process in the factory as the model was obsolete one & not in manufacturing range.

Subsequent to installation, high-voltage testing was conducted in accordance with IEC 62271203 standards and GIS bays are now operational catering to the power transfer requirements of already commissioned generating unit. The transition from long-term storage to operational readiness posed multiple challenges, including component obsolescence, limited OEM support, and long procurement lead times. Despite these hurdles, the GIS system could be successfully commissioned, thus demonstrating the effectiveness of methodical project management and targeted refurbishment.

This case study serves as a benchmark for the restoration of GIS systems subjected to prolonged storage or other adversities. It highlights the importance of strategic planning, technical innovation, and resource optimization in reviving dormant infrastructure. The paper includes comprehensive data, insights, and photographic documentation, offering valuable guidance for future projects facing similar challenges in the T&D sector.