In this paper new on-line field ground fault location method for synchronous machines in combination with field ground fault protection can determine and locate faults in rotor winding. Static excitation is field winding is supplied from rectifier through excitation transformer. Melody of this technique is it can locate position of fault in field winding online reducing forced outage. Principle of this method relies on analysis of ac & dc components of field voltage and voltage across grounding resistance situated in neutral of excitation transformer. This method is analyzed through simulation. resistance. NOMENCLATURE V ac -AC component of grounding resistance voltage.V dc -DC component of grounding resistance voltage. V dc0 -Maximum value of V dc V fdc -DC component of excitation voltage. V fac -AC component of excitation voltage. R g -Grounding resistance. R f -Fault resistance. X -Rotor winding position expressed in percent.