A fault detection and isolation (FDI) system for monitoring the stator current and voltage sensors of a doubly-fed induction generator (DFIG) for wind energy applications is presented. The FDI system is based on the model of the balanced three-phase signals, that is used to design a residual generator resting on the so-called Generalized Observer Scheme (GOS). Next, a decision system made of a combination of vector CUSUM (Cumulative Sum) algorithms is used in order to process the residual vector and achieve detection and isolation of incipient additive faults. The approach is validated via simulations of the DFIG controlled by a Linear Quadratic Gaussian (LQG) regulator.