Study of the operating conditions of a distribution network fragment with the selecting optimal strategy for its development
Students Name: Kalynevych Rostyslav Yuriiovych
Qualification Level: magister
Speciality: Electric Power Stations, Networks and Systems
Institute: Institute of Power Engineering and Control Systems
Mode of Study: full
Academic Year: 2022-2023 н.р.
Language of Defence: ukrainian
Abstract: Distribution electric networks are electric networks that are designed to transmit electric energy from sources of production to sources of consumption, including distribution between specific consumers [1-4]. Specific technical requirements apply to the operation of these important elements of the electric power system. One of the main ones is the provision of reliable and uninterrupted electricity supply to consumers. An important criterion for the efficiency of the operation of the electrical network is the ability to operate without failure during a given period of time. The necessary indicators of the quality of electrical energy with minimal losses of active power should also be provided [2-4]. The main problem of the current state of electrical distribution networks is the obsolescence of their electrical equipment, when there is a constant increase in the electrical load [3]. Outdated equipment, primitive schemes and the same constructive implementation of distribution networks are the main reasons for large losses of electrical energy, unsatisfactory reliability of power supply, high costs for emergency and restoration work and for compensation for losses to consumers from emergency undersupply of electricity, low level of safety of operation of the electrical network. The task of the qualification work is to choose the optimal strategy for the development of a fragment of the real distribution network of 6 kV, which is fed by the 110/35/6 kV Substation №165 "Komarno". The studied electrical network is characterized by the following features: significant lengths of its individual lines with uneven loading of their individual fragments; the electrical network is built using the trunk principle; significant physical and moral wear and tear of electrical equipment; large voltage losses, which leads to unsatisfactory voltage levels on consumer power buses; low automation of electrical network facilities with large interruptions in power supply to consumers; large technological and commercial losses of electrical energy. Study object – a fragment of the 6 kV electrical network of PJSC "Lvivoblenergo", which is connected to the buses of the "Komarno-165" substation. Scope of research – established operating modes of the investigated part of the electrical network and their optimization. Goal of research – establishing the operating conditions of the studied fragment of the 6 kV electrical network and choosing the optimal strategy for its future development. According to the results of the research analysis of the maximum load regime for the existing 6 kV electrical network, we see a significant over-normative decrease in voltage levels on the tires of many consumers. This already significantly complicates the operation of the investigated power grid and is accompanied by significant losses of active power. Prospective load growth will only deepen the problem, will be accompanied by a significant deterioration in the quality of electric power, therefore, a further radical change in the configuration of the studied fragment of the power grid is inevitable. In order to improve the operational characteristics of the existing part of the power grid, its mode parameters were investigated under the condition of switching to a voltage of 10 kV. According to the results of the research analysis of the maximum load regime for the reconstructed electrical network at a voltage of 10 kV, we can see a significant reduction in technological losses of active power (by 57.2% compared to the original circuit at a voltage of 6 kV), and the voltage levels of the most distant substations are within acceptable limits (maximum recorded voltage deviation does not exceed 7.2%). Based on the analysis of the functioning of the reconstructed power grid at a voltage of 10 kV, we make a decision about the possibility of optimizing its mode parameters by changing its structure. According to the results of a series of studies on the optimization of the network structure according to the criterion of the minimum loss of active power, its optimal configuration was determined. For the reconstructed electrical network at a voltage of 10 kV and optimization of its structure, we see a significant reduction in technological losses of active power (by 32.8% compared to the original reconstructed circuit at a voltage of 10 kV and by 71.2% compared to the original circuit at a voltage of 6 kV) , the maximum recorded voltage deviation does not exceed 4.0%. Having analyzed the possible options for increasing the efficiency of distribution electric networks, the expediency of the reconstruction of the electric network by switching to a voltage of 20 kV was investigated. The conducted studies showed a reduction in active power losses: by 84% compared to the original circuit at a voltage of 6 kV; by 61.7% compared to the original circuit at a voltage of 10 kV; by 45% compared to the optimized circuit at a voltage of 10 kV. The voltage deviation at the transformer substations farthest from the power supply center will not exceed 2%, which will allow the 20 kV power grid to function normally even with a prospective increase in power consumption.