Analysis of harmonics in switching transients of an integrated steel plant — A case study

In a distribution network of a large utility like an integrated steel plant, the major electrical machinery like distribution transformers are often subjected to normal and abnormal voltage and current stresses due to frequent switching operations. In this paper we simulate a portion of the distribution network of Durgapur Steel Plant using MATLAB 7.9 and observe the effects of switching of feeders, reactors and capacitors at a particular transformer terminal. Fast Fourier Transform (FFT) has been used to analyze the harmonics contents in the oscillatory switching transients. The results prove that the reported failure of the transformers of above said network is due to the matching of transient frequency to the natural frequency of transformer that is due to part-winding -resonance.