Research on PD sensor design for stator winding diagnosis of turbine generators

Directional coupler type PD sensors have been used for recent decade to diagnose stator winding of operating turbine generators. Most of these sensors are designed as a transmission line structure, like micro-strip line for efficient matching at sensor output. However the thin sensing conductors of these sensors make a lot of losses when sensor receives coupling signals from windings. In this paper, authors simulated electric field distributions of stator slot structures under the PD incoming situations through the windings. From there, CPW type sensors which have similar transmission field distribution to stator slot structures as well as Slot-GND type sensor which can maximize coupling power of sensing signals are designed and fabricated. The sensitivities are tested on the real sized model of stator winding and slot; consequently, the measured signal of novel type sensor shows higher peak level shape and power spectrum than others.