The increasing growth of doubly-fed induction generators (DFIG) in wind farms requires attention to understanding its short-circuit behaviour in order to meet grid code requirements. The DFIG model has been well known for years, but many application uncertainties still persist and their impact on short-circuit calculation has to be fully understood. This paper attempts to clarify the influence of different DFIG models on simulation results obtained from DIgSILENT PowerFactory. It further investigates the short-circuit model of DFIG under various operating conditions and its implication on protection relay settings.