Fault Diagnosis in Rotor Windings in DFIG using Magnetic Flux Measurement Coil Antenna

Nowadays harnessing electric power through wind is one of the most important forms of sustainable power production. A doubly fed induction generator is commonly used in wind turbines, however short circuit fault of rotor windings severely affect its performance. So for this purpose, an experimental platform has been designed to detect the inter turn short circuit fault in rotor windings in doubly fed induction generator using a magnetic flux measuring coil antenna. The experimental platform has the following nameplate data: 100 kW wound rotor induction machine, supply voltage 400V, rated speed 1800 rpm, stator/rotor connection $\Delta/\mathbf{Y}$ and rated current 129/45 amp. The experimental setup comprises of the following subsystem: a motor to drive the generator, a condition monitoring system to acquire the date, a control system to regulate the speed and to perform the short circuit fault, a short circuit cabinet to make connection between the generator and control system. The experiment was performed at a no load, 25 kW and 50 kW load conditions. A magnetic field measuring coil antenna having a frequency range of 20 Hz - 500 kHz was placed on the axial side of the generator to acquire the output voltage. An obvious change in the amplitude of output voltage at frequencies of 250 Hz, 270 Hz and 280 Hz was observed, when the inter turn short circuit fault occurred. Which serves as a clear indication of the short circuit fault in the windings. The amplitude at these frequencies increases as the fault level increases, which is helpful for testing the fault severity. The results show that monitoring the search coil voltage is more effective and advance way than the motor current signature analysis to detect the inter turn short fault in rotor windings in doubly fed induction generator.