Ground Faults Location in Poles of Synchronous Machines Through Frequency Response Analysis

Abstract

Synchronous generators are key pieces in any power system. Therefore, it is essential to have effective protection and diagnosis techniques for these machines. Ground faults are the most common issue in rotor windings and several damages can be originated if a second fault occurs, consequently, the detection of the first one is crucial. After detecting the existence of a ground fault, its location would be helpful to reduce the time needed to repair the machine. This article presents a new ground fault location method in field windings of synchronous machines based on the frequency response analysis. The method provides an estimation, not only of the location of the faulty turn but also of the fault resistance. The method is based on the utilization of the resonance frequency as a distinctive parameter. The construction and fitting of some curves, where resonance frequency against fault resistance for each turn is collected, allows the fault location. This technique has been developed and successfully corroborated carrying out numerous experimental tests in a pole of a large hydro synchronous generator. Applying six different fitting techniques to reduce errors from fault curves, PCHIP and modified Akima methods provide better results than the others tested.