Abstract
The demand to improve grid infrastructure is of utmost importance especially with the increased expansion and addition of distributed generation units to cope with today's era of transforming to smart grids. The health status of distribution transformers in an electrical grid plays a vital role in maintaining network service continuity, safety from catastrophic events, and reliability of utility operation. Monitoring transformer's health is essential for minimizing outages and extending its life in service. Various diagnostic tests and fault detection techniques have developed to effectively support utility operators in predicting failure, estimating life expectancy and condition monitor its status. For these reasons, traditional and advanced methods are required to reduce maintenance time, cost, and help in finding fault causes and location easily. This paper gives a thorough overview about widely used and latest condition monitoring techniques while highlighting strengths and limitations of each.