The methods of analysis of transients in three-phase circuits with distributed parameters and interphase connections are considered on the basis of representation of such circuits by multipoles, finding their corresponding concentrated parameters and determination of boundary and initial conditions of transients. The formulation of this scientific problem is justified by the current trend in theoretical electrical engineering to consider multiphase circuits as a series-parallel connection of different n-poles, which improves the calculation of transient electromagneticprocesses in multiphase circuits with distributed parameters and interphase connections. Using thetheory of multipoles allows us to represent the elements of the electric circuit by macromodels thatreflect their external connections and the impact on the rest of the circuit. The main difficulty inapplying this principle is to resolve emerging electromagnetic bonds.
Global trends of increasing the buildings energy efficiency are aimed at reducing energy use to nearly zero consumption (nZEB). Achieving the nZEB level requires the implementation of a set energy-saving measures to improve the thermophysical properties of fences, building engineering systems and the use of renewable energy sources. One of low-cost and energy-efficient measures to increase the level of energy efficiency of buildings is the introduction of energy-efficient intermittent heating modes of buildings. Usually, this measure is appropriate and possible after the thermal modernization of the building. Determining the energy performance of buildings for the introduction of intermittent heating modes requires the use of mathematical models. The paper compares the application of different mathematical models and methods for estimating thermal energy savings in thermal modernization and implementation of intermittent heating modes based on the quasi-stationary model according to DSTU B A.2.2-12: 2015, stadium model created on the basis of RETScreen software and dynamic model 5R1C according to EN ISO 13790 and EN 13786. Heat-accumulation properties of building enclosures in RETScreen are not taken into account, in DSTU B A.2.2-12: 2015 - are taken into account for external enclosures, 5R1C - both internal and external enclosures are taken into account. The calculation was made for a residential building and a gymnasium located in the city of Kyiv. The introduction of a set of measures for thermal modernization of building fences will reduce heat consumption by 60 and 35% for residential building reinforced and gymnasiums, respectively. Introduction of intermittent heating modes for buildings after thermal modernization / modern buildings allows to save on heating more than 15% - determined on the basis of RETScreen program, 10% - on the basis of dynamic grid model 5R1C, 22% - on the basis of quasi-stationary method according to DSTU B A.2.2- 12: 2015, for a residential building and a gymnasium building located in Kyiv.
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