yazdan ashgevari

Phase Unbalance in distribution networks is one of the unavoidable problems that results from presence of single-phase charges and diversity of consumption among customers. This paper aims to study unusable capacity in distribution transformers due to phase Unbalance through proposing a new coefficient for estimating their capacity. In this study, the primary reasons which lead to Unbalance in transformers have been studied, then unusable capacity in transformers and phase Unbalance index have been formulated , and finally, real results on two posts related to Ardabil electricity distribution network have been evaluated, information corresponded to sample posts has been acquired through installing data logger machine, type TDL 104 for a week and using hour-to-hour sampling method. The results form machine have been analyzed using Matlab software, and then related diagrams have been drawn and also comparison among them has been done. Finally, the effect of phase Unbalance in estimating transformers’ capacity has been proposed by a coefficient.

In this paper, the multi-objective PMU placement is presented. Two objectives are fulfilled simultaneously which are the minimization of the equipment installation cost (i.e. minimizing the number of installed PMUs) along with the maximization of the system measure redundancy index which is equal to the maximization of system’s reliability. Moreover, the limitation on the number of PMU measurement channels is investigated for fulfilling the total system observability and increasing the measurement redundancy. In a power system, transformers tap is employed as an equipment for voltage regulation, however, the variation signal of this parameter is not mostly sent to the central control which leads to a severe disturbance in state estimation program. Consequently, transformers tap observability should be considered in PMU placement problem. Accordingly, a virtual bus is added to the grid in order to model the variant transformer tap. Due to the advantages of meta-heuristic methods, the multi-objective Gray wolf algorithm based on dominancy and Pareto criteria concepts is applied.

Phase Unbalance in distribution networks is one of the unavoidable problems that results from presence of single-phase charges and diversity of consumption among customers. This paper aims to study unusable capacity in distribution transformers due to phase Unbalance through proposing a new coefficient for estimating their capacity. In this study, the primary reasons which lead to Unbalance in transformers have been studied, then unusable capacity in transformers and phase Unbalance index have been formulated, and finally, real results on two posts related to Ardabil electricity distribution network have been evaluated, information corresponded to sample posts has been acquired through installing data logger machine, type TDL 104 for a week and using hour-to-hour sampling method. The results form machine have been analyzed using Matlab software, and then related diagrams have been drawn and also comparison among them has been done. Finally, the effect of phase Unbalance in estimating transformers’ capacity has been proposed by a coefficient.