Investigation the causes of Transformers Failures in Mellitah Complex - case study

Power transformers play a critical role in the distribution and management of electrical energy, making their reliability and longevity of paramount importance. However, transformers are susceptible to various types of failures, which can have significant impacts on power systems. A better understanding of the common causes and impacts of transformer failures, as well as methods to improve their performance, is essential for maintaining the reliability and stability of electrical power systems. The power system network of Mellitah Complex, in the "north part of Libya", experienced a number of transformer failures. In this paper, several tests and analyses have been conducted to identify the causes of failure of the transformer in the power system, and to avoid these breakdowns in the future. Also, present two case studies on unexpected failures of power transformer tag No: 40-920-ET-061B and a generator power transformer tag No: 40-910-ET-011B in the Mellitah complex during regular operation. The research is done based on the data that are gathered from several events of transformer failure and tests. The tests are; Insulation Resistance measurement test (IR), phase conductor ohmic resistance, winding resistance test, the transformer voltage ratio test, the time of oil regeneration test, dielectric strength test, IR tests conducted at 5000V for 1 minute, and voltage injection test (ratio test). The investigation showed that the main cause of the malfunction of transformer tag No: 40-920-ET-061B is the entry of water from the rusty roof into the middle HV winding. Additionally, because of not following the maintenance procedures by the maintenance team led to the mysteries of the main cause of the failure of transformer tag No: 40-910-ET-011B.