Live tank CO2/02 range update from 72 kV up to 420 kV

European Union's energy policy is advancing decarbonization efforts by establishing clear objectives for reducing CO2 emissions in the forthcoming years and decades. The high-voltage industry is encouraged to innovate and create alternatives to equipment relying on SF6 gas.

For Live Tank (LT) circuit breaker equipment, a gas mixture of CO2 and O2 emerges as a more environmentally friendly option compared to SF6, offering a feasible alternative in high-voltage electrical applications. In live tanks, air serves as the insulating medium, unlike Gas Insulated

Switchgear (GIS) and Dead Tank (DT) systems, which require insulation between the active component and the metallic enclosure. The CO2/O2 gas mixture has been researched and optimized to meet the performance requirements for live tanks, functioning effectively at temperatures as low as -50°C. This mixture is now preferred by several high voltage equipment manufacturers worldwide for LT insulation and switching functions. The development of high voltage products using these gas mixtures has received consistent financial backing from the

European Union LIFE program and ADEME for Project FRANCE 2030. This technology has already been implemented in live tank applications up to 145 kV, with the choice of targeting now the 420 kV voltage level driven by the substantial SF6 volume and numerous existing SF6 circuit breakers in Europe.

This paper outlines the development status of the live tank circuit-breaker 420 kV 50 kA 50 Hz, showcasing the capability of CO2/O2 technology to match SF6 performance while preserving the same size. Noteworthy accomplishments include the successful interruption of short line faults and terminal faults. The project benefits from co-financing by the European Commission under the LIFE program and its Climate Change Mitigation sub-program (LIFE2020 CCM-FR001749 - LIFE SF6-FREE HV BREAKER project). The system's minimum operating temperature is -50°C, and its performance is anticipated to be realized using the same physical dimensions as existing SF6-based circuit breakers.

The development of high-voltage circuit breakers utilizing CO 2/O2 gas mixtures involves several performance extensions to address the diverse requirements of international markets and specific applications.

For the Canadian market, advancing circuit breakers to 362 kV and 60 Hz in compliance with

IEC standards signifies a major technological leap. This adaptation ensures reliability and adherence to IEC standards at 60 Hz while optimizing energy efficiency and minimizing greenhouse gas emissions.

Enhancing performance capabilities to include voltage levels of 170 kV, with breaking currents of up to 40 kA or 50 kA, provides opportunities to improve system robustness with single chamber circuit-breaker.

The focus on developing reactor switching circuit breakers targets the unique requirements of switching inductive loads. This extension improves the control of transient phenomena, ensuring safe and reliable operation in networks with reactors, thereby enhancing overall system performance and stability.

In summary, over the next few months, the CO2/O2 LT range will expand to cover the market for 170 kV and 420 kV complementing the existing coverage at 72.5 kV and 145 kV.