SF₆-free GIS

SF₆-free GIS

Special Edition - Substations

Technically advanced and SF6-free 145 kV blue GIS


SF6, the most commonly used arc extinguishing and insulating gas in gas-insulated switchgears (GIS), is a greenhouse gas with high global warming potential, requiring careful handling throughout its life cycle. In order to reduce the GIS-related global warming impact, innovative solutions using alternative gases have been developed by different manufacturers, especially the blue GIS from Siemens – available for 145 kV / 40 kA / 3150 A – with clean air insulation and vacuum switching technology shows many technical advantages.

Keywords: high voltage gas-insulated switchgear, GIS, vacuum interrupter, clean air, SF6 alternatives

1. Introduction

Today, SF6 is by far the most globally used medium for arc extinguishing and insulating gas in high-voltage switchgears. Its excellent technical properties have been proven in high voltage applications for more than 50 years.

SF6 requires careful handling throughout its life cycle to prevent gas leakage into the atmosphere, as it is a high global warming potential (GWP) greenhouse gas with a very long lifetime.

In order to improve the sustainability of the energy supply and to reduce the GIS-related global warming impact, research on SF6 alternative solutions have been worked on internationally for years.

The alternative solutions offered today are clean air, CO2 and fluoroketones or fluoronitriles, with mixtures of N2, O2 or CO2, which are used as arc extinguishing and insulating media. On this basis, different products were developed, and first grid applications were started.

In this article, the status of the alternative solutions is summarized from the high-voltage switchgear point of view. On the other hand, the SF6-free 145 kV blue GIS 8VN1 based on clean air and vacuum switching technology is also represented.

2. Status and evaluation of the SF6 alternative gases

The alternative gases available today and their main properties, as well as pros and cons, are discussed in different papers. The decision to use clean air as insulating gas is grounded upon the following core clean air facts:

Clean air consists of 80% N2 and 20% O2, is cleaned from CO2 and almost free of moisture (synthetic air). Clean air has neither global warming potential ((GWP) = 0) nor ozone depletion potential ((ODP)) = 0).