Guidelines for SF6 end-of-life treatment of T&D equipment (>1 kV) in substations

Even considering the very long lifetime of 40 to 50 years for electrical equipment, it is inevitable that equipment will reach their end-of-life (EoL). Alternatively, the gas quality indicates that heavily aged SF₆ must be replaced to extend the equipment lifetime. An unexpected discovery when the SF₆ technology had been implemented in the market was the extremely high global warming potential (GWP) that is 25,200 times the CO2 equivalent. Therefore, emission of the SF₆ gas must be minimised and special precautions are necessary at the EoL management of SF₆ containing electrical equipment, in terms of the final disposal procedures and/or recycling of SF₆ and parts of such equipment.

Transmission System Operators (TSO) and Distribution System Operators (DSO) are electricity utilities with their own service departments and established experience in the handling of SF₆ equipment and SF₆ gas. This is not the case across the entire power industry as there are many smaller companies with perhaps only a few SF₆ installations, far fewer handling experience and service personnel. For these companies, an environmentally sound EoL treatment guide is of great benefits. For distribution equipment, the quantity of SF₆ per asset is relatively low for equipment at lower voltage levels due to their compact design. However, the number of units installed is extremely high, so the overall quantity of SF₆ used in MV and HV is more or less the same. Therefore, it is imperative to develop guidelines that inform end-users the appropriate steps for all SF₆ assets across different voltage levels to ensure minimal SF₆ emissions.  

This guide summarises the well-known practices and inform the EoL procedure of handling electrical equipment containing SF₆ and the SF₆ itself. Every step of the process is explained in detail, from the preparation until recycling or final disposal. The target is to limit the SF₆ emissions in every step of the processes dealing with the disposal of equipment parts and/or the recycling of SF₆ used in all equipment reaching their EoL to the absolute bare minimum that is technically achievable. Importantly, safety must be guaranteed in every single step.

Checklists at the end of the brochure will support streamlined preparation of the work and in selecting appropriate partners to perform the work in the most professional and cost-effective manner. It needs to be highlighted that avoiding emissions of SF₆ is stipulated in various regulations and local laws, and therefore this guide helps to comply with these rules and regulations to prevent sanctions or penalties for owners or operators of electrical equipment, and crucially avoid undesired impacts to the environment.

The brochure starts with some definitions on electrical equipment types and common technical expressions used throughout the Technical Brochure. Large HV switchgear are well known as products containing SF₆ in high quantity, but also smaller equipment such as ring main units or even...