THREE PHASE TRANSFORMERS AS HARMONIC SOURCES IN POWER SYSTEMS.
The generation of harmonic voltages and currents in three phase transformers is analysed and an equivalent third harmonic source is developed. A bank of three phase connected single phase transformers, shell type or five limbed as well as core type three phase transformers are considered. An equivalent circuit which allows for different winding connections is also developed. The parameters of this equivalent circuit are obtained either from measurements with the aid of a harmonic analyser or by calculation. It is shown that although these harmonic sources are generally speaking small in the case of core type transformers, enhancement of these voltages is possible when near resonance occurs with system capacitances. The developed models are supported by measurements.