11 Power Distribution Transformer Insulation Assessment for Prevention of Potential Failure to Enhance Power Quality S. Tom-Davies 1* , D. C. Idoniboyeobu 2 & S. L. Braide 3 1,2,3 Department of Electrical Engineering, Rivers State University, Port Harcourt, P.M.B.5080, Rivers State, Nigeria * Corresponding Author Email: tomdaviesseipiribo@gmail.com ABSTRACT This research provides dielectric assessment of power distribution transformer overall insulation integrity with breakdown voltage and partial discharge test as an important aspect of detecting insulation defects as well as problems relating to poor design in high voltage transformers. Knowledge of the conditions under which different types of decomposing activities are likely to occur, measures are taken to ensure against premature system failures resulting to insulation defects. A non-destructive partial discharge measurement introduced along with phase-resolved partial discharge pattern were analyzed to establish the condition of a high voltage electrical transformer insulation system. This research work gives an in-depth assessment of dielectric insulating oil and partial discharge measurement technique to investigate transformer insulation integrity so as to ensure system reliability for improved power quality. Despite the high BDV value of 77.9kV, it still recorded a 73.58pC on injecting a 19.00kV RMS for 500kVA/33, 0.415kV. Results obtained in this research work clearly demonstrate that notwithstanding the impact of dielectrics strength on transformer oil as regards insulation, confirmed that elevated breakdown voltage test value does not completely guaranty good insulation nor detect defects such as bubbles, cavity and voids that occurs within the high voltage transformers insulation. However, partial discharge measurement with MPD/MI software reveals all forms of insulation problems including design errors, thereby increasing transformer optimization and reducing down time. This technique is used to determine if partial discharges are occurring above a certain value when predetermine voltage is applied on the system. Keywords: Insulation assessment, Failure prevention, Partial discharge, Transformer, Power improvement 1. INTRODUCTION Distribution transformers are very crucial in deciding the power flow in a large power systems when implementing the installation of an electrical transformer, several tests are conducted to determine the electrical, mechanical and thermal suitability for the system where they will be applied and used. In recent development of electrical power systems, power plant capacity growth has been a major achievement in the power industry. This power is conveyed at a voltage higher than the generated voltage with the consideration of losses along the line, to lessen the force misfortune along the transmission lines, the high voltage transmission is done at low current. However, for this reason, transformers are generally utilized in the electricity distribution subsector. The motivation behind power distribution transformers is to lessen the essential voltage of the electrical circulation framework to a use voltage that serves the consumer [1], [8], [13]. Transformer has no moving parts, aside from the tap transformers, cooling fan and siphon engines. Thus, it cannot easily breakdown like other rotatory machines. Utilizing considerable protection against copper winding, laminated core and other significant parts, transformers are designed to endure endlessly. International Journal of Innovative Scientific & Engineering Technologies Research 10(2):11-21, April-June, 2022 © SEAHI PUBLICATIONS, 2022 www.seahipaj.org ISSN: 2360-896X