Future-Ready T&D Assets: Overcoming Challenges in AIS and GIS Substation Transformation

High-Voltage Alternating Current (HVAC) Air-Insulated Substations (AIS) and Gas-Insulated

Substations (GIS), alongside large electrical equipment such as transformers and reactors. While these substations form the backbone of long-distance power transmission, their construction and commissioning pose significant challenges technical, administrative, environmental, and safetyrelated that can adversely impact project timelines, costs, and operational reliability.

This paper presents practical insights drawn from multiple large-scale HVAC AIS and GIS substation projects, focusing on critical challenges encountered during construction, installation, and commissioning phases, and the solutions that enabled successful project completion. The discussion is anchored on detailed case studies that illustrate real-world issues faced in diverse project environments, ranging from complex terrains and adverse weather conditions to stakeholder management and equipment-specific risks.

One of the primary challenges highlighted is the impact of site and soil constraints. Many substations are located in areas with difficult terrain, high water tables, or poor soil bearing capacity, which affect foundation stability and civil works, particularly for heavy equipment like transformers, reactors, and

GIS modules. Design and engineering coordination across disciplines civil, structural, mechanical, and electricals is another key focus, as inadequate integration can lead to design clashes, construction delays, and rework. The paper emphasizes the need for robust interface management practices and early-stage design validation to avoid such issues.

Equipment handling and erection present their own set of challenges. The transportation, lifting, and installation of heavy, sensitive components especially in space-constrained sites such as hydroelectric projects require careful planning, specialized equipment, and adherence to safety standards. The paper further explores the logistics and coordination complexities involved in multi-stakeholder projects, where collaboration with contractors, equipment manufacturers, and local administrations is essential for on-time execution. 1 The paper also examines the challenges of on-site testing under adverse environmental conditions, such as high humidity and dust, which can impact the accuracy of test results, especially for GIS bays, transformers, and reactors. Additionally, safety considerations are thoroughly addressed, given the inherent risks of high-voltage substation construction, including work at heights, confined space operations, and live equipment exposure.

The discussion is brought to life through detailed case studies, including:

1) Installation of a 1500 MVA, 765/400/52 kV ICT 2) Challenges of electrical/ground clearance on a split-level terrain.

3) Root cause analysis and recovery from a fire incident in a 220 kV GIS LCC panel.

4) Investigation and mitigation of a flashover in a 132 kV GIS disconnector.

5) EHV cable laying operations under severe space constraints.

In conclusion, the paper underscores the need for meticulous planning, proactive risk management, environmental impact mitigation, and stringent safety practices. The lessons learned provide valuable guidance for future HVAC AIS and GIS substation projects, offering practical solutions to minimize risks, control costs, and ensure timely project delivery. This knowledge sharing contributes to advancing best practices in the global power sector.