IDENTIFICATION ERROR OF UNBALANCE VOLTAGE SOURCES IN POWER SUPPLY SYSTEMS BY THE DISTORTING NODAL CURRENT CRITERION
One of the properties of electrical energy, that causes significant economic losses for both suppliers and consumers of electricity, is voltage unbalance. The most universal criterion for identifying voltage unbalance sources is the nodal distorting current. The accuracy of its determination depends on the method of measurement organization and is characterized by the greatest error for the local approach. The reason for this lies in an approximate method for determining the equivalent circuits of consumers of electrical energy and their parameters when measuring the parameters of the network operation mode only at one point of common connection to the power supply system. Analysis of the influence of approximate equivalent circuits and their parameters on the determination of the nodal distorting current showed that adequate identification of the sources of voltage unbalance distortion is possible only in the reverse sequence. At the same time, it is difficult to accurately determine the error in calculating this criterion in real time measurements due to the presence of additional unknowns that are required for its calculation. Based on this, it is proposed to carry out an upper estimate of this error. This required the introduction of additional functions with the search for their maximum under the given constraints. In addition, the uncertainty associated with the non-zero value of the identification criterion for a non-asymmetric consumer of electricity was taken into account that led to the need to introduce a dead zone for it. As a result of the studies carried out, expressions were obtained for an upper estimate of the error in determining the criterion for identifying sources of voltage symmetry distortion in the reverse sequence and determining its dead zone in real time measurements in relation to three-phase three- and four-wire power supply systems.
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