A new method for evaluating the effects of model uncertainties on a detection residual in a Fault Detection (FD) procedure is proposed in this paper. Structured uncertainties are considered in a discrete-time interval model of the system. They are characterised by means of input disturbances and the covariance matrix associated with the nominal model parameters. A global fault detection method is then developed. It consists in generating a detection residual by the generalisation of previous work established for continuous-time domain [6] and in deciding on the fault occurrence.