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Purpose. The article discusses new strategies for controlling distribution networks with different, active components using synchronized measurements of voltage and current phase values (magnitude and phase angle) based on the use of high precision micro-synchrophasors (uPMUs), which are adapted to work in distribution networks. Particular attention in the article is focused on the problem of mislabeling of phases and load balancing of distribution network feeders. Methodology. Elements of the optimization theory and matrix calculation were used to develop optimization criteria for initial load balancing problem and minimum switching load balancing problem. Results. The article considers approaches to solving problems arising in distribution power grids under conditions of growth of distributed generation levels. The factors leading to increased uncertainty in forecasting distribution network modes that complicate the tasks of power equipment diagnostics, network topology identification, state assessment and fault location are established. Problems of incorrect phase marking and load symmetry of distribution network feeders are analyzed in detail. Authors proposed an approach to phase identification and feeder load symmetry using micro-synchrophasor data (uPMU) based on the analysis of voltage measurements. The proposed approach is based on comparing the measurements made at the beginning of the feeder with the measurements made in other locations of the feeder considering the constant phase angle shifts of voltage multiples of 30 degrees, which are caused by the phase shift of transformers. The peculiarity of the proposed approach is the ability to solve the problem of phase marking and phase identification using the measuring bodies of uPMUs with accuracy within 1 degree. As a result, based on the information about the actual phase markings, the authors proposed an approach to feeder load symmetry, which is based on solving the optimization problem. The optimization criterion is the minimum by the sum of the norms of the vector of the feeder phase loads for a certain period of time. This article investigates an approach to phase identification in three-phase distribution networks based on the analysis of micro-synchrophasor measurements (uPMU). The proposed approach is based on direct voltage measurements at different feeder locations, taking into account the fact that in an unbalanced three-phase system the time series voltage values at the two ends of one phase should have a much stronger correlation than at the two ends of different phases. This feature makes it possible to solve the problem of marking and identification of phases when using uPMU measuring bodies with accuracy within 1 degree. The proposed approach takes into account, in multiples of 30 degrees, the phase shift due to the presence of D-Y transformers. The proposed approaches will be investigated when creating a monitoring system for electric distribution networks using uPMUs at the pilot site of the Igor Sikorsky KPI campus and elsewhere in cooperation with network operators. Originality. In contrast to the known methods and approaches to the phase identification, proposed method using direct measurements of three phase voltages and thus obtained results do not contain uncertainty. Practical value. Solving the phase marking problem also reduces the number of errors in power equipment diagnostics, network topology identification, condition assessment and fault location. References 11, figures 4.

The charging currents of EHV transmission lines cause the Ferranti effect, which causes an increase in voltage at intermediate points transmission line. The work aims to study the laws of the voltage distribution along the line route and to develop a method for determining the coordinates of a point with extreme voltage. Methodology. Mathematical modeling of long-distance transmission lines in Wolfram Mathematica allowed to form the laws of the voltage distribution along the line and determine the coordinate of the extreme point on the voltage. Results. It is shown that the application of the traditional model of idealized power transmission causes high modeling accuracy only in the modes of unloaded line and low loads. In the range of medium and high loads, the simulation error reaches unacceptably large values. The paper proposes more accurate models for determining the coordinate of an extreme voltage point: linearized and second- and third-order models. It is shown that the proposed models are characterized by higher accuracy in a wide range of loads. Increasing the degree of the model results in higher accuracy, but is associated with an increase in the cumbersomeness of the mathematical model. It is shown that first and second-order models provide sufficient accuracy for typical designs of 750 kV power transmission lines. It is shown that neglecting the losses on the corona has almost no effect on the accuracy of calculating the coordinates of the extreme point on the voltage, which simplifies the linear calculation model and models of the second and third-order. Originality. Mathematical models of the first, second and third orders have been developed for high-precision determination of the coordinate of a voltage-extreme point along a long-distance transmission line. Practical significance. The offered mathematical models are intended for application in problems of regulation and adjustment of parameters of flexible power transmissions. Ref. 12, figure, tables 4.