User Guide for Non-SF6 Gases and Gas Mixtures in Substations

Gas-Insulated Switchgear (GIS) has been widely deployed since the late 1960s due to its compact design, high reliability, resistance to environmental influences and enhanced personnel safety. Sulphur hexafluoride (SF₆) has played a key role as a dielectric and arc-quenching medium in medium- and high-voltage switchgear, offering excellent electrical, thermal and interruption performance. However, SF₆ is a potent greenhouse gas, and its environmental impact has led to increasing regulatory pressure worldwide, including the European Union’s F-gas Regulation (EU) 2024/573 and regulations introduced by the California Air Resources Board.

In response, extensive research and development over recent decades has resulted in viable alternatives to SF₆, notably fluorinated gas mixtures and natural-origin gas mixtures used in combination with gas or vacuum interrupters. These alternative gases fulfil the primary functions of insulation and current interruption but introduce different physical, chemical and operational characteristics that must be addressed in equipment design and operation. Key technical considerations include modified interrupter designs to account for different arc-quenching performance, altered sealing requirements due to gas permeability, gas decomposition behaviour, and the need for gas concentration measurements in multi-component mixtures.

This user guide provides practical guidance for the application, handling and management of non-SF₆ gases and gas mixtures in high-voltage switchgear. It covers gas handling procedures, handling equipment, gas measurements, tightness requirements, environmental, health and safety aspects, as well as end-of-life treatment and recycling. The guide complements existing international standards such as IEC 62271-4 and recent IEC and IEEE developments, and builds on established best practices from decades of SF₆ experience as documented in relevant CIGRE Technical Brochures. Its objective is to support utilities, asset owners and service providers in the safe, reliable and environmentally responsible deployment of non-SF₆ insulating and switching technologies.