eng Science and Education Publishing American Journal of Electrical and Electronic Engineering 2328-7357 2018-03-23 6 1 28 31 10.12691/ajeee-6-1-4 AJEEE2018614 article khalaf Y. Alzyoud yasin_mualla@yahoo.com 1 Electrical Engineering Department, Faculty of Engineering Technology, Al-Balqa Applied University, Amman, Jordan This work focus on observation of the insulating system and analysis of the insulation resistance measurement results in 110kV, 20 and 63 MVA oil-immersed power transformers are presented. The observation was undertaken from the start-up and it includes graphical and numerical values obtained by measurements, the analysis of the state of insulation provides possibilities to undertake remedial action in due time with the aim to extend the transformer life. http://pubs.sciepub.com/ajeee/6/1/4/ajeee-6-1-4.pdf contribution transformer estimation insulation oil transformer