The review and analysis the destructive effects of harmonics on a sample MV/LV transformer

Abstract

Considering the effects of non-liner loads to create harmonics and replacing these loads instead of household, commercial and industrial customers, create many voltage disturbances every year. Harmonics will cause specific problems in the power distribution networks. Some of these problems could be unsuitable function of equipments from these networks, decreasing their lifetime and their efficiency. Therefore, we need to study harmonics and show the way to resolve these problems. Limiting harmonics is very important for utility companies and their subscribers. Utility companies must provide against to damage on subscribers from these problems. Since Utility companies could not guarantee a sine wave to protect their subscribers from voltage disturbances; therefore, these subscribers must limit their disturbances of their equipments. One statistics indicated twenty-five percent of transformers utilized in the utility companies of Iran have about eighteen year's lifetime only. So, maintenances of transformers in the utility companies become very important. Once we replace one of these transformers, we need to analysis its malfunction. The study of malfunction will provide us with a reasonable solution. Therefore, we are trying at this paper to show why we need to study the effects of harmonics on transformers of power distribution networks. The effects such as increasing load and no-load power losses, reducing the power of transformers and Destructive Effects create more heat in them. Consequently, we identify and record harmonics on a sample load and calculate Destructive Effects that created in its transformer by these harmonics, at this condition, be increase the transformer's heat by non-liner loads, to cause its insulation life decrease as well as transformer life.

Evaluation of the Influence of Non-sinusoidal Conditions on Power Transformers

“…As seen from the Table, the non-sinusoidal current increases total ohmic losses by 14.5 kW. Table 5 demonstrates eddy current losses in transformer windings and its other components that are calculated by (6)(7)(8)(9)(10). An increase in the eddy current losses under non-sinusoidal conditions compared to the sinusoidal ones is 399.0 kW.…”

“…This accelerates the aging process of insulating paper, transformer oil, and magnetic system. Recently, there has been a growing interest in evaluating the influence of harmonics on power transformers, as evidenced by the papers of the international conferences [10][11][12][13][14][15][16] This paper provides an overview of the characteristics used in publications to evaluate the influence of harmonics on transformers. The results of their calculations are presented.…”

Research into harmonic power in the high- voltage networks

“…Active power of harmonic orders h>1 does not perform useful work in the conventional power systems except heating and lighting in special cases. In [9], [10], the authors discuss additional losses of harmonic active power in electrical networks and equipment. In [11], "harmonics were found to be responsible for 5.4% of all power quality costs".…”