A technique for on-line detection of incipient faults in the windings of turbine - generator rotors has been developed based on the twin signal sensing method. To detect the developing shorts in any winding, two identical pulses are applied to both ends f the winding and are reflected back .Any abnormality in the winding results in the applied signals being reflected through nonsymmetrical circuits. The difference between the reflected signals are amplified and used as signature signal for further processing. This paper describes the development of power electronic circuits for generation of the twin signals and detection of the reflected signals. The design and fabrication of a lab model to test this technique is summarized along with the results of laboratory experiments. The issues involved in using the developed technique for practical applications are addressed and the limitations of the technique are summarized.