Analysis of transformer inrush transients in offshore electrical systems

Large transformers are electrically close to generators in an offshore powe r system. Energising such transformers causes significant inrush currents, which are sustained for several seconds. The voltage dip on the generator b us then initiates a response from the automatic voltage regulator (AVR). Us ing a numerical simulation, the lightly damped response of the AVR is shown to modify the inrush transient. Other on-line transformers can be sent int o magnetic saturation. Site measurements confirm the features of the transi ent predicted by the simulation. The paper shows that a detailed model is r equired if the inrush current on an isolated offshore power system is to be correctly predicted.