High-voltage circuit breakers (HVCBs) are crucial for power system reliability, yet diagnosing their mechanical failures is a significant challenge due to their complex design and unique operating conditions, especially when facing new, unseen fault types. To address this challenge, we propose a novel zero-shot HVCB fault diagnosis method, named X-SAM, leveraging the Xception network and self-attention mechanism (SAM). X-SAM aims to identify new, unseen fault classes solely using known class fault samples during the training phase. X-SAM innovatively combines adaptive feature extraction from multi-source signals and a novel attribute learning system that maps these features to a universal set of fault attributes. This enables the diagnosis of new fault types by analyzing the similarity between predicted attribute vectors and a predefined attribute matrix. Demonstrated through zero-shot diagnosis tasks on multiple HVCBs, X-SAM not only successfully identifies unseen faults using limited data but also paves the way for cross-domain applications, offering a significant advancement in HVCB and electrical equipment fault diagnosis.