Fault Detection in Three-Phase Rotating Machines

Three test methods are proposed which are suitable for detecting turn faults in large three-phase rotating machines. According to these methods, the difference between the terminal voltages of two phases is monitored while either one phase or two phases simultaneously are excited. The excitation voltage may be a surge or a sinusoidal wave of a specified frequency. Results are discussed for the cases with and without the rotor in place as well as with solid and incipient faults. The detection procedure is simplified by an indicating-lamp go/no-go type fault indicator.