Power distribution transformers using natural ester fluids as dielectric and coolant oleh Jorge Iván Silva-Ortega, Jhon Zapata-Rivera, Jhon Edwin Candelo-Becerra, Nivaldo Rosales-Hernández, Samir Francisco Umaña-Ibáñez, Mario Andrés Mejia-Taboada, Alan Rafael Palacio-Bonill, Melissa Torregrosa Rosas