Technology innovation of VI(Vacuum Interrupter) and challenges for the Eco-friendly power equipment industry in Korea

VCB technology was further incorporated into gas-insulated switchgear (GIS), contributing significantly to the enhancement of operational stability and reliability within the Korea electric distribution system.

Beginning around 2010, driven by growing environmental concerns and regulatory initiatives,

SF₆-free switchgear and GIS technologies employing alternative insulation media, such as dry air and solid insulation, were introduced. These technologies became mandatory by 2020 under

Korea government regulations. This strong regulatory framework has accelerated the development of environmentally sustainable VI and VCB technologies, extending their application to voltage classes of 38 kV and 72/84 kV. Consequently, these advancements have contributed to the modernization and global advancement of power grid infrastructure, particularly in the context of environmentally responsible electrical networks.

More recently, environmental regulations have been extended to extra-high-voltage (EHV) power systems. Korea’s transmission and distribution utility, Korea Electric Power Corporation

(KEPCO), has conducted pilot operations of 170 kV SF₆-free gas-insulated switchgear (GIS) since 2018. Following the prohibition of SF₆ usage in 2024, 170 kV GIS employing alternative insulating gases, such as the NOVEC™ series, has been adopted as an interim solution.

However, from a long-term perspective, the development of GIS based on vacuum interrupter

(VI) technology with a global warming potential (GWP) of zero is strongly required.

Accordingly, extensive research and development efforts are currently underway. Key technical challenges include the saturation of dielectric withstand capability in vacuum with increasing electrode gap length, capacitive current switching performance, continuous current performance with respect to thermal characteristics, and the mechanical integrity of highpressure VI.

This paper presents the development status of interruption units for 170 kV GIS utilizing commercially available VI that have reached the commercialization stage. In particular, among the technical challenges impeding the adoption of environmentally friendly circuit breakers, capacitive current switching performance, especially BC2 class duty (close–open operation under back-to-back capacitor bank conditions), is investigated. Performance verification results obtained from 24 kV distribution-class equipment, together with test results of a 170 kV ecofriendly circuit breaker, are presented, followed by a discussion of future development directions.