Internal short-circuit faults in proton exchange membrane (PEM) electrolyzers develop rapidly and pose severe hazards. Rapid and reliable fault identification is crucial for enhancing hydrogen production system safety. Therefore

this paper investigates the characteristics and protection methods for internal short-circuit faults in PEM electrolyzers. Firstly

based on the fundamental principles of electrolytic hydrogen production and polarization characteristics

an equivalent circuit model for the PEM electrolyzer

which accounts for the electric double-layer capacitance effect

is established. Building upon this

combined with DC-DC converter control strategies

a precise calculation method for the transient and steady-state characteristics of electrolyzer internal short-circuit faults is proposed. Based on fault characteristics

protection criteria utilizing steady-state current variation and the sign feature of power variation are proposed

with their operating boundaries analyzed. Finally

extensive simulations demonstrate that the proposed fault analysis method achieves an average relative error below 5% for transient current and below 1% for steady-state current. The proposed protection strategy accurately identifies internal short-circuit faults in PEM electrolyzers.