en Harmonics Harmonics Research Paper Research Paper <div style="text-align: justify;"><span style="color:#000000;"><span style="font-family:Times New Roman;"><span style="font-size:14px;"><span style="line-height:115%"><span new="" roman="" times="">The progressive application of non-linear loads in distribution systems (DS) increases current harmonics flow in DS&#39;s apparatuses, especially distribution transformers (DTs). Since DTs&#39; operating temperature rises due to the harmonics flow, their loading should be reduced such that the hot spot temperature (HST) is preserved under its permissible value. This means that DTs&#39; available capacity is influenced by load harmonic content. In this paper, a novel formulation for DTs&#39; failure rate in the presence of harmonics is presented as a function of load harmonic contents. Using the suggested equivalent failure rate, DTs&#39; available capacity in harmonic polluted DS is mathematically formulated. Additionally, the presence of the harmonic increases the HST, leading to DTs&#39; aging acceleration. Therefore, the impact of harmonic components on DTs&#39; aging is arithmetically modeled. To evaluate the efficacy of the suggested reliability model, it is applied to three distinct DTs having respectively industrial, commercial, and residential loads. The obtained results indicate that the available capacity of DTs with the same rated capacity would be different regarding to their load harmonic contents. On the other hand, it is comprehended from the achieved results that the aging acceleration factor (Faa) of the DTs increases owing to their load harmonic contents.</span></span></span></span></span></div> Available capacity,distribution transformer (DT),harmonics,aging,reliability assessment. 85 97 http://ijeee.iust.ac.ir/browse.php?a_code=A-10-2329-3&slc_lang=en&sid=1 Hassan Alizadeh Shyrayeh alizadeh.h@mazust.ac.ir 1800319475328460013371 1800319475328460013371 No University of Science and Technology of Mazandaran, Behshahr, Iran Iraj Ahmadi iraj.ahmadi@mazust.ac.ir 1800319475328460013372 0000000190213277 Yes University of Science and Technology of Mazandaran Mohammad Mirzaie mirzaie@nit.ac.ir 1800319475328460013373 1800319475328460013373 No Faculty of Electrical and Computer Engineering,Babol Noshirvani University of Technology, Babol, IranPost Code: 47148 – 71167 Masoud Ahmadi gorji ahmadigorji@yahoo.com 1800319475328460013374 1800319475328460013374 No Department of Electrical Engineering, Mahmudabad Branch, Islamic Azad University, Mahmudabad, Iran