Structural formula for SF6

The US Department of Energy’s (DOE) Advanced Research Project Agency-Energy (ARPA-E) has selected four projects to receive a combined $9.4 million to develop technology focused on removing sulfur hexafluoride (SF₆) from the US power grid.

SF₆ has been the standard gas used inside high voltage electrical equipment as an insulating and arc-quenching medium. However, SF₆ is also an extremely potent greenhouse gas with 23,500 times the comparative Global Warming Potential of CO₂ and a lifetime of 3,200 years in the atmosphere.

The four projects selected to receive funding include the University of Connecticut in Storrs, Conn.; Georgia Tech in Atlanta, Ga.; GE Renewable Energy’s Grid Solutions business in Charleroi, Pa.; and Toshiba International Corporation in Houston, Texas.

University of Connecticut. Detection and Fixation: A Lifecycle-Management Framework Towards an SF₆-Free Green Power Network – $2,734,381
The University of Connecticut proposes to develop a life-cycle management framework to accelerate and safeguard the transition of the US power grid toward a sulfur hexafluoride (SF₆)-free green power network.

Studies suggest GE’s alternative environmentally friendly gas mixture g³ (green gas for grid) as a promising potential replacement for SF₆. The team will focus on leaks, aging byproduct detection, and fixations (capture and storage) for g³, but believes its proposed sensing technologies and life-cycle management can be implemented on all types of equipment. The technologies can be extended to retrofit existing assets for SF₆ leak detection and end-of-life fixation.

Georgia Tech. TESLA: Tough and Ecological Supercritical Line Breaker for AC – $3,428,827
Leakage from SF₆-insulated circuit breakers and power equipment has been raising environmental concerns due to the high GWP of SF₆. Georgia Tech proposes TESLA, an SF₆-free high-voltage circuit breaker.

Recent breakthroughs in the dielectric properties of supercritical fluid research show the promise of using it as a dielectric and arc-quenching medium for high-voltage AC circuit breakers instead of SF₆. TESLA opens possibilities for an SF₆-free electric apparatus. The team will design and build the proposed circuit breaker rated at 245 kV, 4 kA and validate the design and functionality using a synthetic test circuit.

GE’s Grid Solutions. Development of an Eco-friendly Outdoor HVAC Power Circuit Breaker to Reduce Dependence on SF₆ Technology in the U.S. Electrical Grid – $2,259,041
GE’s Grid Solutions plans to develop a SF₆-free high-voltage AC outdoor dead-tank power circuit breaker. The circuit breaker will be rated at 245 kV and will also provide the basis for a two-break 550 kV rated design. It will use g³ gas mixture for current breaking and dielectric withstand.

This project is a critical step in launching a range of products that meet US energy industry requirements without using SF₆ technology. These products are essential to reduce the bulk electric system’s carbon footprint and greenhouse gas emissions. The resulting products will be manufactured in the US.

Toshiba International Corporation. Novel Approaches toward Improved Thermal Interruption Performance of. CO₂+O₂ Natural Origin Gas Mixtures for Replacement of SF₆ in High Voltage Equipment – $990,713
Using natural-origin gas mixtures of CO₂ and O₂ instead of SF₆ gas in transmission and distribution circuit protection devices could reduce GWP from 25,200 to less than one. CO₂-based gas mixtures have reduced thermal interruption performance compared with SF₆.

To achieve higher interruption ratings with CO₂-based gas mixtures, Toshiba plans to (1) gather baseline thermal interruption data using an upgraded model circuit breaker with state-of-the-art architecture, (2) apply a novel interrupter architecture with external and persistent magnetic fields to improve arc cooling and reduce reliance on forced gas flow, and (3) design a novel contact system to minimize metal vapor production during arcing.

*Original article online at https://www.greencarcongress.com/2021/10/20211006-sf6.html