Normal Operation Of Transformer Research Articles

Analysis for Temperature Rise of a Three-Phase Four Limbs Transformer by Soil Structure with DC Bias

In this paper, a method for earth potential computation of layered soil structure is discussed. To calculate thermal field of the transformer with dc bias, simulation models using MAXWELL and COMSOL are proposed. Based on the electromagnetic analysis, electric power loss resulted in temperature rise is calculated. Under the case of normal operation of transformer, a research was carried out to compare the abnormal changes of temperature of transformer. It worked out that if there are different DC parts in transformer, the loss will increase with DC bias and the temperature of transformer core will also increase. If it is increasing continuously and no preventive measures are taken soon, the thermal aging of some parts in transformer will speed up and gradually affect the normal operation of transformer. The research lays the groundwork for further research of transformer DC bias and aging.

DC reactor type transformer inrush current limiter

A new inrush current limiter (ICL) is presented to limit the inrush current of transformers. The proposed ICL consists of three similar sets. Each set includes a diode-bridge and a single DC reactor and is connected in series with the individual phases of transformer. The ICL has almost no effect on normal operation of transformer. It needs no control, measurement and gate driving system and has a simple power circuit topology. The equivalent instantaneous inductance of transformer is used for analysis of circuit operation. The theoretical analysis, design features, power losses and voltage distortion because of using ICL are presented. The proposed method has been tested by simulation and laboratory experiments. Both results show that the proposed ICL successfully limits the inrush current.