Distribution transformer model for transient studies

Abstract

Distribution transformers are expensive components in the distribution network of the country. Records from Ceylon Electricity Board show that considerable numbers of failures of these distribution transformers are due to lightning surges. This is a huge cost for the utility suppliers like Ceylon Electricity Board (CEB) and Lanka Electricity Company (LECO). The study area of distribution transformers under transient conditions needs to be broadened and availability of a transformer model to represent a distribution transformer used in Sri Lankan network is very much essential. If there exists a model with acceptable level of accuracy to represent the distribution transformer under transient conditions, many criteria relating to the distribution lines can be studied without actually implementing them. In this research, a methodology is presented to obtain a model to represent a distribution transformer under transient condition. Parameters are calculated and a model is presented based on the details of the 160 kVA, 33/0.415 kV, distribution transformer. The same methodology can be extended to obtain the respective models of distribution transformers with other power ratings. The proposed model is simulated using the PSCAD software and output results are obtained when the standard lightning waveform and chopped surge waveforms are input to the model. The simulated output along the transformer winding is observed and compared with the result of an already carried out experiment presented in a research paper. Both the simulated and experimental outputs took fairly the same shape and the model is validated. Key words: Transformer Model, Surge Distribution, Winding, Simulations