Specific Features of Application of Current and Voltage Transducers When Calculating Eletrical Network Unbalance

Purpose of research. The purpose of this article is to consider the main features of the application of current and voltage transducers determining the electrical network unbalance factor. Also, an important issue is the value of measuring instruments inaccuracy, at which there is no impact on the unbalance factor determining.

Methods. The article describes classifications of main current and voltage transducers. An example of the implementation of one of the voltage transducer and analog-to-digital converter variants is shown. The essence of the process of balancing is explained, various unbalance factors are considered, explanatory formulae are provided. The main requirements for current and voltage measurement circuits and for computational signal processing are mentioned. In particular, such important points as determining the phase angle, determining the network parameters and consideration of the influence of measurement errors on the determination of the unbalance factor are studied. The issur of determining the phase angle is considered and the need for its determination is indicated. It is explained that when determining the network parameters, high precision of measurement is required.

Results. The impact of the instrumental error of measurements on the determination of the unbalance factor is considered, and instruments rating below which an error may occur while finding the unbalance factor is determined. When determining the instrument rating at which an unacceptable error occurs, a probabilistic model of power distribution of a three-phase network is mentioned; a graphical description of this model is given. Determining the sets of unbalance factors before balancing, after balancing and after balancing taking into account the error, is provided. It is mentioned that in determining these sets, weights are used as increasing and decreasing factors for the terms included in the set. The factor showing the percentage of the decrease of unbalance changes due to the effect of the error is introduced. The dependence of this factor on the measurement error is considered.

Conclusion. A conclusion on the value of the error which does not impact the determination of the unbalance factor is provided.

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