RESEARCH OF SYMMETRIC COMPONENTS OF VOLTAGE IN THE DISTRIBUTION NETWORK 0,38 / 0,22 KV
DOI:
https://doi.org/10.31734/agroengineering2019.23.090Keywords:
current asymmetry, voltage asymmetry, loss of electrical energyAbstract
The article deals with the problem of asymmetrical modes in 0,38 / 0,22 kV networks. It is shown that the asymmetry of the currents is caused by the work of communal-household load, the main part of which is unevenly distributed in the phases of single-phase electric receivers. Determining the amount of asymmetry in the network allows specifying of the level of electricity losses. In some electricity companies, losses in the 0,38 / 0,22 kV networks reach up to 15 % of the electricity supplied to the grid, and the electricity quality indicators exceed the allowable values by 2 – 4 times. In European countries, it is considered that if electricity losses exceed 7 – 9 %, then such electricity transmission is considered inefficient. Therefore, it became necessary to develop new methods and measures to improve the quality of electricity and to take appropriate measures to reduce losses.
The research proposes a mathematical method for calculating the symmetric components of the 0,38 / 0,22 kV network voltage, which can be the basis of a mathematical apparatus for developing of a software product, designed for calculation of voltage asymmetry. It is shown that in the system of symmetric coordinates the corresponding current and voltage matrices contain components of forward, reverse and zero sequences. It was also investigated that the resistance of the straight and zero sequences of the three-phase line is calculated or experimentally studied, with the resistance of the forward and reverse sequences for the lines being the same, and the resistance of the zero sequence can be 2-3 times greater than the resistance of the direct sequence. It is caused by the difference in the values of the emf mutual induction, induced in the phase by currents of direct and zero sequences flowing in the other two phases.
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