Challenges and Precautions During Design and Engineering of Gas Insulated Switchgear (GIS) Substation of Hydro Projects

A Gas Insulated Switchgear (GIS) substation is a type of electrical substation that uses SF6 gas insulation between HV components. GIS substation offer numerous advantages such as space savings, reduced maintenance requirements and improved reliability, however they also come with their own set of challenges. Design and engineering of a GIS at Hydro projects involves specific challenges, that requires own set of precautions to ensure successful execution and hence successful operation for a long time.

Generally Hydro projects have limited space availability. Sometimes the power plants are constructed inside long tunnels to achieve the desired Water head level. This makes it very challenging to accommodate the GIS equipment and associated components in the tunnel owing to space constraints.

Due to very limited availability of space inside the tunnel, usually the equipments like Turbine, Generator, Generator Transformers, GIS etc. are placed on floors of a Multi-storey building, inside the tunnel. The compact design of GIS helps to mitigate this challenge to some extent, but still needs careful planning and optimization of available space for proper placement of GIS.

While designing GIS in a hydro project, various challenges including panels/equipment placement, accessibility and design of EOT crane, interfaces with balance equipments, civil interfaces, cable routing and optimisation, coordination with other stakeholders, O&M, Health Safety and Environment are to be taken care of.

The objective of this paper is to share project experience, challenges faced and precautions taken during designing the 245kV GIS in Hydro project where available space is even less than the standard space available in similar projects. The paper also explores the possibility to be used as a benchmark for similar arrangements considering space constraints and possibility to design the project in lesser space, that may result in saving of huge civil costs involved in a underground hydro project.

As a case study, one such underground power house has been discussed in detail to highlight the challenges faced during layout design, and the resolutions to deal with the challenges.