In corridors with high lightning ground flash density and unfavorable soil resistivity, backflashover remains a dominant outage mechanism for overhead transmission lines below 500 kV.
Fuse is one of the oldest selectivity arrangements in overhead line protection, yet it remains a persistent source of nuisance fuse blowing and unexplained outages.
Transmission-line fuses are thermal protective devices whose health state is directly encoded in their operating temperature and current history. Conventional maintenance—periodic inspection or reactive replacement after failure—leaves latent degradation undetected. This article outlines a condition-assessment framework that exploits continuous temperature–current monitoring to quantify fuse aging and schedule replacement before failure.
Fuse interrupting capacity on transmission and subtransmission lines is increasingly outpaced by rising fault levels. Network reconfiguration, new generation interconnections, and lower-impedance transformer designs routinely push available short-circuit currents beyond the published interrupting ratings of legacy expulsion fuses—often in the range of 8–16 kA for older cutout designs, while modern current-limiting backup units are rated to 50 kA and, in select platforms, up to 100 kA.
Dropout fuse cutouts deployed above 2,000 m face an aging regime fundamentally different from that at sea level. UV intensity rises by approximately 10–12% per 1,000 m of elevation, while air density and convective cooling capacity fall in parallel.
Lightning remains the leading cause of unplanned outages on overhead transmission and distribution lines worldwide. The economic consequences are substantial: nuisance fuse operations, transformer failures, and sustained interruptions impose significant costs on utilities and degrade customer satisfaction. Effective lightning protection requires more than installing surge arresters at every structure or simply upgrading fuse ratings.
