This paper presents a method to identify synchronous generator parameters from on-line data measured at the terminals of the machine. An observer for estimation of synchronous generator damper currents is designed and implemented. The observer-estimator is used in a Graphic User Interface (GUI) application. Possible internal machine fault conditions can be detected and remedial action can be applied. Noise filtering and bad data detection and rejection are implemented to increase the reliability of the estimates. Saturation of the synchronous generator inductances is also considered. Secondary objectives include calculation of the error characteristics of the estimation, development of an index of confidence, study of the observability of generator parameters, and evaluation of alternative GUI features.