Stator-Ground Fault Location Method Based on Third-Harmonic Measures in High-Impedance Grounded Generators

Third-harmonic based schemes are used to detect stator-ground faults in high-impedance grounded generators. These methods use third-harmonic voltage measures in the neutral and in terminals to detect faults. As third-harmonic voltage levels are different according to each generator and operational point, simulations, studies and tests need to be carried out to ensure that the chosen third-harmonic scheme is able to cover the portion closest to neutral while the conventional method (59GN) covers the portion closest to the stator winding terminals. This paper presents the solution of the third-harmonic generator model used for a stator-ground fault study in terms of the mesh currents and uses the derived equations to develop a third-harmonic based fault location method. The fault location method was tested over 1785 simulations and presented a maximum error of 0.004 p.u., determining the fault location accurately.