A 0.4 kV distribution network equipped with an automated information and measurement electricity metering system is considered. It is assumed that the metering system receives data on active and reactive power, and on the effective voltage values that correspond to the same time interval and are received at the distribution network beginning and from all subscribers. It is also assumed that the impedances of the phase wires are the same for each inter-subscriber section of the network, but differ from the impedance of the neutral one and are considered to be unknown during the initial calculation. The problem is formulated as follows: arrange, by means of the metering system, online calculation and monitoring of non-technical losses of electric energy in the network that contains several simultaneously operating subscribers connected to the network phases, from which incorrect energy consumption data are received. It is also necessary to identify such subscribers and evaluate the amounts of their unauthorized taps of electricity. The known approach to solving the formulated problem is analyzed, and its shortcomings are revealed. A new method is proposed, which is based on taking into account the phasor relationships for the operating parameters that determine the three-phase network electrical state and calculating the impedances of the distribution network inter-subscriber sections when there are no unauthorized taps of electricity and the currents through these sections when there are unauthorized taps of electricity. By using the proposed method, it becomes possible to determine non-technical losses of electricity in the distribution network for the reporting period and to identify subscribers with incorrect electricity consumption data. It is shown that the unaccounted consumption of electricity in each individual subscriber can be calculated if there are several subscribers with unauthorized taps of electricity connected to one phase of the network, whereas there are no more than one of such taps in the other phases. The obtained results can find application both in existing automated electricity metering systems and in the development of new ones.
Four-wire distribution electrical networks of 0.4 kV equipped with automated systems of electrical energy accounting are considered. The problem of identifying the resistances of the wires of the distribution network is solved on the basis of the effective values of voltages and currents, as well as of their phase shift angles obtained by the accounting system in the power supply node of the network and from its subscribers for the selected observation intervals. A brief analysis of the known methods and technologies used in this area of research is carried out. The importance of the formulated problem for applied problems, such as control and diagnostics of electrical energy losses, as well as the technical condition of the network, is noted. A method (algorithm) is proposed that allows determining unknown, unequal complex resistances of inter-subscriber sections of the distribution network. In these resistances, the reactive components are considered equal within the inter-subscriber section; the active components differ due to the influence of unequal flowing currents and/or weather factors. At the same time, data from two different network operating modes are required, which are selected based on the analysis of the dynamics of changes of supply currents and/or voltages by the accounting system device connected to the power supply node. Considering that the active resistances of the wires must remain unchanged, the mode that is used for calculations is the one that is before the change in power consumption in the network and the next one immediately (about 0.1 s) after it. An example of a calculation that demonstrates the reliability of the proposed equations of the method that has been developed on a simulated distribution network is given. The research results are focused on the improvement of automated accounting systems and the implementation of their new functions that elevate the reliability of distribution networks, as well as allowing for the rapid identification of non-technical losses of electrical energy.
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