The Estimation of the Influence of Each Harmonic Component in Load Unbalance of Distribution Transformers in Harmonic Loading Condition

Nowadays, due to their widespread utilization, transformers are considered as the main component of distribution networks. Despite the important role playing by transformers, some problems e.g. flow of high-range current from transformers' null despite balancing the currents of phases has been observed in the appropriate utilization of distribution transformers. This phenomenon is observed in most distribution stations. Although the presence of single- phase loads causes an unbalance in transformers; load displacement and network balancing lead again to the flow of huge current from transformers neutral. One of the its reasons can be the usage of distribution transformers in harmonic load condition, in three-phase distribution networks load current harmonics in transformers' neutral have negative considerable consequences. Therefore, it is required to evaluate and analyze the harmonic effects in the presence of nonlinear loads. since the harmonic component playing an important role in the creation of load unbalance, it is necessary to evaluate them; these components have considerable roles in the selection of compensation methods in the process of harmonic contamination especially the selection of compensator filters. In this paper, by Matlab/Simulink stimulation capability performed as real-time to examine the reasons for increased flow of neural coil of the transformer in a harmonic environment and evaluate the influence of each harmonic component of load flow in the creation of unbalance and neutral flow of transformer. The information of harmonic load includes the range of harmonic component and its angles from outflow current of a static transformer. The load's current has a harmonic component of 3, 5, 7, 9, 11, 13, 15 order in addition to range in main frequency (50Hz). The results show that the unbalance of the transformer's load in harmonic load condition has increased by 1.529%. In addition, the share of each harmonic component depends on their angle in addition to the range such that the impact on the main frequency is much higher than other harmonic components, which is due to asymmetry and phase difference between phases.

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