Slot discharge signal patterns in high voltage machines

Surface damage to coil sides in the slot section of a high voltage stator winding may be a result of movement induced by electromagnetic forces. Characteristic partial discharge signal patterns associated with this kind of damage have been reproduced in an experimental model. The model has also demonstrated that measured discharge amplitudes are dependent upon the effective value of corona screen resistance associated with the discharge current and that this in turn is influenced by the degree of surface damage. Finite element analysis has been used to obtain a nonlinear R-C transmission line model of the degraded corona screen from which predictions of discharge signal patterns may be obtained for different degrees of surface damage.