This paper reports the study carried out to asses the dynamic behaviour of a real wind farm during fault conditions in the distribution network. The objective is to obtain a transient model valuable for all kinds of operational conditions. The paper begins with a detailed modelling of the distribution network between the wind farm common busbar and the point of common coupling with the HV transmission system, for all types of short-circuits. The state-space network model, together with the electromagnetic transient model of each wind generator, configure a multi-machine wind farm model, with 572 state variables. Simulation results prove that multi-machine modelling is mandatory in order to tackle the wind farm contribution to symmetric and asymmetric short-circuits. (C) 2011 Elsevier Ltd. All rights reserved.