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• A novel lifetime estimation framework for hybrid HVDC breakers. • Press-pack IGBT module's transient junction temperature solution based on an infinitesimal method and Cauer thermal models. • Analyzing the weakness in the hybrid HVDC breaker and the suggestions for extending the breaker lifetime are given. • The influences of the fault location, the reclosing and the current-limiting reactor on the breaker lifetime are discussed. As an important aspect of breaker reliability analysis, the lifetime of a hybrid high-voltage direct current (HVDC) breaker is estimated in this paper. Based on the equivalent thermal network, the static temperature profiles of the breaker components during normal operation are solved for using an iterative method, and the components' transient temperature profiles during short-circuit faults are computed using an infinitesimal method. Then the computed temperatures are verified via finite element analysis in COMSOL Multiphysics. Considering the influence of aging on the thermal resistances of insulated gate bipolar transistor (IGBT) modules, the lifetimes of the press-pack IGBT modules and arresters in the breaker are estimated using lifetime models and cumulative damage models. In case studies, the weakest link in the breaker and the influences of the fault location, the reclosing and the current-limiting reactor on the breaker lifetime are discussed. The results show that the arresters are the weakest breaker components, and that the fault location, reclosing and current-limiting reactor all affect the breaker lifetime. [ABSTRACT FROM AUTHOR]