Abstract

ASTORGA GOMEZ, Juan Miguel; AROSTICA CORDOVA, Rodrigo Alfonso  and  IRIARTE SALINAS, Yuri Antonio. K factor estimation in distribution transformers using linear regression models. Tecnura [online]. 2016, vol.20, n.48, pp.29-40. ISSN 0123-921X.  https://doi.org/10.14483/udistrital.jour.tecnura.2016.2.a02.

Background: Due to massive incorporation of electronic equipment to distribution systems, distribution transformers are subject to operation conditions other than the design ones, because of the circulation of harmonic currents. It is necessary to quantify the effect produced by these harmonic currents to determine the capacity of the transformer to withstand these new operating conditions. The K-factor is an indicator that estimates the ability of a transformer to withstand the thermal effects caused by harmonic currents. This article presents a linear regression model to estimate the value of the K-factor, from total current harmonic content obtained with low-cost equipment. Method: Two distribution transformers that feed different loads are studied variables, current total harmonic distortion factor K are recorded, and the regression model that best fits the data field is determined. To select the regression model the coefficient of determination R² and the Akaike Information Criterion (AIC) are used. With the selected model, the K-factor is estimated to actual operating conditions. Results: Once determined the model it was found that for both agricultural cargo and industrial mining, present harmonic content (THDi) exceeds the values that these transformers can drive (average of 12.54% and minimum 8,90% in the case of agriculture and average value of 18.53% and a minimum of 6.80%, for industrial mining case). Conclusions: When estimating the K factor using polynomial models it was determined that studied transformers can not withstand the current total harmonic distortion of their current loads. The appropriate K factor for studied transformer should be 4; this allows transformers support the current total harmonic distortion of their respective loads.

Keywords : Distribution transformers; K factor; regression models; total current harmonic distortion.

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