Principles of power factor testing of complete generator stator windings

This is a follow up to a paper presented at the 2002 ISEI Symposium. IEEE 286-2000 -"Recommended Practice for Measurement of Power Factor Tip-Up of Electric Machinery Stator Coil Insulation" provides a section devoted to the power factor testing of complete generator stator windings. This work will review IEEE 286-2000 recommended procedures and present actual findings when these procedures are implemented. Power factor testing of complete stator windings provides data that is limited in its scope and value. Careful analysis of the data is very important and an understanding of what the data is indicating must be interpreted correctly to obtain meaningful results. Power factor data taken on individual stator coils are compared with power factor data measure on complete phase groups in a stator. The effect exhibited by guard electrodes is presented in order to obtain a better understanding of the resulting data. It is the purpose of this paper to draw attention to the value and the limitations of the power factor test when performed on complete windings.