Characteristic of Third Harmonic From Synchronous Generator Passing Through Transformer and Rectifier

The third harmonic has caused much power quality problem in the neutral of distribution system. Salient pole synchronous generator has been recognized as one of the triplen/third harmonic sources. This research is aimed at studying the characteristic of third harmonic from generator flowing through the load directly, via transformer and shunt connection to rectifier. Lab scale experiments have been conducted to vary load impedance and transformer winding configuration. When generator is connected directly to a combined resistive and inductive load, the third harmonic current and voltage depend on the load impedance magnitude and phase angle. Since the third harmonic voltage produced by generator are in phase or zero sequence in nature, the third harmonic current depend on transformer winding configuration, the load impedance magnitude and phase angle. When full-wave bridge rectifier is shunt connected between generator and load, the third harmonic current at both rectifier and load are actually coming from generator that depend on load impedance magnitude and phase angle. It is recommended that the study on third harmonic voltage and current propagation from generator should be done by performing harmonic measurement and analysis at all parts of the network. Third harmonic voltage and current magnitude alone may not give correct indication to their severity because they are vector quantity and rely on zero sequence network, load impedance magnitude and phase angle.