scholarly journals Research of transient processes in case of single-phase insulation faults in low-voltage ship power grids, taking into account the resistance at the fault point

2020 ◽  
pp. 49-54
Author(s):  
И.Е. Кажекин
Keyword(s):  
Single Phase ◽  
Low Voltage ◽  
Experimental Studies ◽  
Power Grids ◽  
Transient Processes ◽  
Safety Issues ◽  
Physical Experiments ◽  
Marine Industry ◽  
Calculation Results ◽  
Constant Potential

В работе рассмотрены вопросы безопасности бортовых электросетей объектов морской индустрии, показано влияние перенапряжений на их основные показатели, которыми определяются опасности смертельных электротравм, опасности возникновения пожаров и взрывов. Представлены результаты математического моделирования электрического разряда по уравнению Майра с учетом особенностей переходного процесса при однофазных замыканиях на корпус. Показана роль напряжения смещения нейтрали по постоянному потенциалу, наибольшие значения которого формируются при неустойчивом контакте фазы с корпусом судна. Описаны результаты экспериментальных исследований переходных процессов, сопровождающихся возникновением неустойчивыми искровыми разрядами. Сравнение результатов расчета по предложенной методике с результатами физических экспериментов показало весьма удовлетворительную сходимость. Предложенная модель может быть использована для уточнения показателей, характеризующих безопасность судовых электросетей. The paper deals with the safety issues of on-board power grids of the marine industry facilities, shows the influence of overvoltages on their main indicators, which determine the dangers of fatal electrical injuries, the risk of fires and explosions. The results of mathematical modeling of an electric discharge according to the Mayr equation, taking into account the features of the transient process in single-phase short circuits to the case, are presented. The role of the bias voltage of the neutral at a constant potential is shown, the highest values ​​of which are formed during unstable contact of the phase with the ship's hull. The results of experimental studies of transient processes accompanied by the appearance of unstable spark discharges are described. Comparison of the calculation results by the proposed method with the results of physical experiments showed a very satisfactory convergence. The proposed model can be used to refine the indicators characterizing the safety of ship power grids.

scholarly journals Selective Identification and Localization of Voltage Fluctuation Sources in Power Grids

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6585
Author(s):  
Piotr Kuwałek
Keyword(s):  
Low Voltage ◽  
Experimental Studies ◽  
Power Grids ◽  
Simulation Studies ◽  
Voltage Fluctuation ◽  
Novel Approach ◽  
Empirical Wavelet Transform ◽  
Power Frequency ◽  
Modulation Signal ◽  
The Individual

The current study presents a novel approach to the selective identification and localization of voltage fluctuation sources in power grids, considering individual disturbing loads changing their state with a frequency of up to 150 Hz. The implementation of the proposed approach in the existing infrastructure of smart metering allows for the identification and localization of the individual sources of disturbances in real time. The proposed approach first performs the estimation of the modulation signal using a carrier signal estimator, which allows for a modulation signal with a frequency greater than the power frequency to be estimated. In the next step, the estimated modulating signal is decomposed into component signals associated with individual sources of voltage fluctuations using an enhanced empirical wavelet transform. In the last step, a statistical evaluation of the propagation of component signals with a comparable fundamental frequency is performed, which allows for the supply point of a particular disturbing load to be determined. The proposed approach is verified in numerical simulation studies using MATLAB/SIMULINK and in experimental studies carried out in a real low-voltage power grid. The research carried out shows that the proposed approach allows for the selective identification and localization of voltage fluctuation sources changing their state with a frequency of up to 150 Hz, unlike other methods currently used in practice.

scholarly journals . Generating maximum overvoltages in ferroresonant processes during single-phase arc shorts in ship low-voltage electrical systems

2020 ◽  
Vol 2020 (1) ◽  
pp. 115-124
Author(s):  
Ilia Evgenievich Kazhekin
Keyword(s):  
Bias Voltage ◽  
Single Phase ◽  
Low Voltage ◽  
Initial Conditions ◽  
Electrical Network ◽  
Electrical Networks ◽  
Electrical Systems ◽  
Zero Sequence ◽  
Constant Potential ◽  
Ferroresonant Circuit

The article discusses processes with single-phase faults in shipboard low-voltage electrical plants with a neutral grounded through a reactor. In such electrical plants, ferroresonant oscillations occur if one of the phases closes to the housing. The oscillations have an influence on the process of generating maximum arc overvoltages during single-phase shorts on the housing. The conditions for appearing ferroresonant phenomena in low-voltage ship electrical networks are studied. The processes in the ferroresonant circuit have been analyzed, the initial conditions necessary for their excitation have been identified. The processes causing the initial conditions in the power supply network that are sufficient for generating ferroresonant oscillations when the phase is closed to the housing have been considered. The conditions favorable for ferroresonant excitation are created due to the behavior of the low-voltage grounding arc and subsequent transient processes in the zero sequence circuit. Maximum overvoltages accompanied by ferroresonant processes occur when the grounding arc is burned in accordance with the theory of Peters and Slepian, that is, when it is extinguished at a moment close to the transition through the zero value of the forced component of the single-phase current short. The arc causes the increased voltages on the neutral grounding elements. As a result, the neutral bias voltage at a constant potential increases significantly. Based on the magnitude of the neutral bias voltage at a constant potential, the effect of ferroresonant oscillations on the maximum overvoltages arising in strong phases is estimated. The quoted formulas help to calculate the maximum values of arc overvoltages. The reliability of the proposed methodology for calculating overvoltages is confirmed by the studies performed on the physical model of the ship electrical network.

Single-Phase Generation Headroom in Low-Voltage Distribution Networks Under Reduced Circuit Characterization

2015 ◽  
Vol 30 (2) ◽  
pp. 1006-1011 ◽  
Author(s):  
Pedro M. S. Carvalho ◽  
Luis A. F. M. Ferreira ◽  
Joao J. E. Santana
Keyword(s):  
Single Phase ◽  
Low Voltage ◽  
Distribution Networks ◽  
Voltage Distribution

scholarly journals Feasibility of Black-Box Time Domain Modeling of Single-Phase Photovoltaic Inverters Using Artificial Neural Networks

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2118
Author(s):  
Elias Kaufhold ◽  
Simon Grandl ◽  
Jan Meyer ◽  
Peter Schegner
Keyword(s):  
Time Domain ◽  
Single Phase ◽  
Low Voltage ◽  
Black Box ◽  
Steady States ◽  
Domain Modeling ◽  
Dynamic Simulations ◽  
Time Domain Modeling ◽  
Artificial Neural ◽  
Grid Side

This paper introduces a new black-box approach for time domain modeling of commercially available single-phase photovoltaic (PV) inverters in low voltage networks. An artificial neural network is used as a nonlinear autoregressive exogenous model to represent the steady state behavior as well as dynamic changes of the PV inverter in the frequency range up to 2 kHz. The data for the training and the validation are generated by laboratory measurements of a commercially available inverter for low power applications, i.e., 4.6 kW. The state of the art modeling approaches are explained and the constraints are addressed. The appropriate set of data for training is proposed and the results show the suitability of the trained network as a black-box model in time domain. Such models are required, i.e., for dynamic simulations since they are able to represent the transition between two steady states, which is not possible with classical frequency-domain models (i.e., Norton models). The demonstrated results show that the trained model is able to represent the transition between two steady states and furthermore reflect the frequency coupling characteristic of the grid-side current.

Adaptive in-situ forecasting for demand-side management in low voltage power grids

2021 ◽  
Author(s):  
Christian Backe ◽  
Miguel Bande ◽  
Stefan Werner ◽  
Christian Wiezorek
Keyword(s):  
Low Voltage ◽  
Demand Side Management ◽  
Power Grids ◽  
Demand Side

Application of Hybrid Biosystems for Stimulation of Oil Production

2021 ◽  
Author(s):  
Baghir Alakbar Suleimanov ◽  
Sabina Jahangir Rzayeva ◽  
Ulviyya Tahir Akhmedova
Keyword(s):  
Oil Recovery ◽  
Single Phase ◽  
Experimental Studies ◽  
Oil Production ◽  
Pore Channel ◽  
Subcritical Region ◽  
Slippage Effect ◽  
Liquid Systems ◽  
Reservoir Conditions

Abstract Microbial enhanced oil recovery is considered to be one of the most promising methods of stimulating formation, contributing to a higher level of oil production from long-term fields. The injection of bioreagents into a reservoir results in the creation of oil-dicing agents along with significant amount of gases, mainly carbon dioxide. In early, the authors failed to study the preparation of self-gasified biosystems and the implementation of the subcritical region (SR) under reservoir conditions. Gasified systems in the subcritical phase have better oil-displacing properties than non-gasified systems. The slippage effect determines the behavior of gas–liquid systems in the SR under reservoir conditions. Slippage occurs more easily when the pore channel has a smaller average radius. Therefore, in a heterogeneous porous medium, the filtration profile of gasified liquids in the SR should be more uniform than for a degassed liquid. The theoretical and practical foundations for the preparation of single-phase self-gasified biosystems and the implementation of the SR under reservoir conditions have been developedSR under reservoir conditions. Based on experimental studies, the superior efficiency of oil displacement by gasified biosystems compared with degassed ones has been demonstrated. The possibility of efficient use of gasified hybrid biopolymer systems has been shown.

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