Twenty-five years using Disconnecting Circuit Breakers: Return of operational experiences from Nordic European utilities

(DCB) technology from Nordic European utilities. The background highlights the inherent limitations of traditional disconnectors – frequent maintenance, reliability concerns and safety issues. The paper’s goal is to present how DCB technology addresses these challenges by optimizing substation designs for enhanced reliability, safety, and economic efficiency.

Operational data reveals DCBs exhibit a significantly lower Major Failure (MaF) frequency of 0.152 per 100 CB-years, nearly three times better than conventional breakers, with no incidents of fire, explosion, or compromised safety procedures. Reliability analyses confirm DCB configurations offer the highest availability and reliability, primarily due to fewer components.

Maintenance benefits include reduced costs through the elimination of numerous exposed mechanical parts and extended, condition-based intervals, with data that confirms substantial annual savings. Utilities behind this paper report high satisfaction and forecast the installation of around 2,000 - 3,000 new DCB units within the next decade. Ongoing development of SF6free DCBs is expected to contribute further to the energy transition while keeping a high level of reliability, safety and economic efficiency for the grid.