Low Voltage Electrical Networks Research Articles

Low voltage electric distribution network planning with demand control

Low voltage electric distribution network planning with demand control

Study of the variation of operation of a low voltage electric network due to the integration of distributed energy resources—Steady state condition

Distributed energy resources (DERs) can significantly impact distribution networks, necessitating characterization studies to understand the technical consequences in various operating conditions. Existing literature primarily applies deterministic or probabilistic techniques for modeling and simulating networks and DERs, but lacks studies that integrate multiple DERs simultaneously. Additionally, assessing various indicators is necessary to determine the influence of DERs on network operation. Furthermore, resilience approaches often overlook DER integration as a disruptive event. To address these gaps, this work employs deterministic, probabilistic, and harmonic distortion analyses to characterize the impact of photovoltaic systems, storage units, and electric vehicles on a reference low voltage network. The study investigates how these DERs influence network operation at different time intervals throughout the day. By examining parameters and indicators (PaI) such as RMS values of voltages and currents, voltage unbalance, and harmonic distortions, the individual and collective effects of DERs are estimated. An adapted resilience evaluation technique groups the PaI values to generate a representative population of a single R indicator for each hour, allowing for quantification of network operation variations. Data for the analysis is obtained through PowerFactory-Python co-simulation, encompassing twenty operating scenarios.

Battery-Based Energy Storage System from Solar Panels Utilization for Worship House Applications in Carang Wulung Village

Due to the topography and hilly terrain in the area, there is still a hamlet in Carang Wulungvillage that does not have a low-voltage electricity network from PLN, namely Gondang Hamlet. As a result of this limitation, there is a place of worship (musala) in Gondang Hamlet that has not been adequately taken care of and is considered unfit when viewed from the availability of electricity. The community in this predominantly Muslim hamlet experiences lighting problems during congregational prayers at night until dawn. The lack of a power source for speakers also prevents the use of speakers to mark the prayer times. Based on this background, a battery-based energy storage system from solar panels was developed for this community service activity. The stages of community service activities carried out include surveying the needs for the installation of solar panel and battery installation systems, assembling several system components, testing the laboratory-scale system, installing the system that has been assembled and tested, and conducting socialization and training for residents on the use, operation, and maintenance of the solar panel system. The residents are happy that this community service activity has been carried out because they can worship comfortably at any time without relying on PLN as a source of electricity

Evaluation of additional electricity losses in electric networks using a meter

In this article, additional electricity losses are calculated using the voltage imbalance factor. There is also a method for predicting extra losses in the case of longitudinal and transverse asymmetry, as well as information on how to measure power quality indicators. It is suggested that home appliances be used to monitor a separate power system's power quality indicators. The findings of investigations on the condition of asymmetry conducted in operational low voltage electrical networks are presented, along with an illustration of how to calculate additional electricity losses in low-voltage networks. In this article for this purpose, the author developed a Malika device, which is fully capable to measure, store, analyze, and draw conclusions from the results of all electrical quality indicators.

A Device for Decreasing Loss in Electric Networks Containing Unbalanced Nonlinear Load

Matters concerned with controlling the operating modes of low-voltage electric networks are discussed. Thus, 0.4 kV electric networks are characterized by significant emission of additional current sequences generated by unbalanced nonlinear load. A versatile compensating device filtering additional power flows caused by unproductive fundamental and higher harmonic current components is proposed as a technical means minimizing the undesirable consequences of additional current load. A method and calculation software were developed, using which the operating mode of a 0.4 kV electric network section was studied with the possibility to incorporate a simulation model of the proposed device. The compensating device parameters are calculated proceeding from the unbalanced power consumption in the network section considered. By using the MATLAB software package, time diagrams visualizing the variation of the studied indicators have been obtained. The economic efficiency of the proposed versatile device for decreasing electric energy loss has been estimated.

Method of creation of power sources for home appliances under constraints of limited resources

The subject of study in this article is the voltage ranges, methods, and tools for prototyping independent sources of power supply and artificial lighting for home appliances with reuse of only widespread components. The goal is to improve the efficiency of the creation and use of independent power supply sources for home appliances. Task: to analyze the history of the development of voltage standards for households; analyze existing autonomous power sources and types of batteries; analyze different loads; find rational voltage ranges based on fundamental values; analyze charge control and balancing circuits for lithium-based batteries; propose the technique of prototyping independent sources of power supply based on reused lithium-ion (Li-ion) accumulators; provide an example of the practical application of the results of research. According to the tasks, the following results were obtained. The evolution of voltage standards of electrical supply networks is analyzed. Types of autonomous power supplies, including pure sine versions, are discussed. The analysis of batteries for autonomous power sources of different chemical compositions is performed. It is proposed to use the water analogy of current and area as an analogy of battery capacity for visual representation of electrical processes. Models of constant current consumption and constant power consumption are considered. It is proposed to reduce the internal resistance of the battery assembly by parallel connection of the reused lithium-ion accumulators. Correspondence of voltage ranges of sequential connection of lithium-ion cells to ensure compatibility with existing devices is investigated. Rational parameters of voltage ranges to ensure compatibility of lithium-ion and acid accumulators with the ability to charge directly from solar panels without a charge controller are found. Charge controllers, battery management systems (BMS), and battery balancing circuits are analyzed. A set of steps for reuse of lithium-ion accumulators for the creation of autonomous power sources is proposed. Conclusions. The main contribution of this research is the proposed method of creation of power supply and interior lighting based on the reuse of accumulators without additional components. The discovered and proposed magic numbers of 3, 5, 7, 9, 11 and 13 for series connection of lithium-ion cells allows to obtain the equivalent of standard voltage ranges of 12 V, 19 V, 27 V, 36 V, 42 V and 48 V. The proposed technique of adjusting the voltage of the passive balancer allows adding 4.5 % to the capacity of the battery assembly. The described solutions allow to build the completely scalable autonomous low-voltage electrical supply network with the ability to charge directly from solar panels without expensive charge controllers.

Expert System Integrating Rule-Based Reasoning to Voltage Control in Photovoltaic-Systems-Rich Low Voltage Electric Distribution Networks: A Review and Results of a Case Study

Nowadays, in low voltage electric distribution networks, the distribution network operators are encountering a high number of connected small-scale distributed generation units, mainly photovoltaic prosumers. The intermittent nature of the prosumers, together with the degree of uncertainty of the requested and injected powers associated with all end-users from low voltage electric distribution networks, can cause voltage variations that violate the allowable limits. In this context, this paper developed an efficient and resilient expert system integrating rule-based reasoning applied to the on-load tap changer-fitted transformer to improve the efficiency of the voltage control in the PV-rich LV EDNs. An in-depth analysis based on 75 scenarios, resulting from the combinations of three indicators—the penetration degree of the photovoltaic prosumers, the consumption evolution associated with the consumers, and the energy production of the photovoltaic systems—was performed to demonstrate the efficiency of the proposed expert system in a low voltage electric distribution network from a rural area belonging to a Romanian distribution network operator. The success rate of the expert system was 86.7% (65 out of 75 scenarios did not have voltage issues). All voltages were between the allowable limits in 100% of the time slots associated with the analysed period. For the other scenarios (representing 13.3%), voltages were inside the range [−10%, +10%] in at least 95% of the time slots.

A Hybrid Approach for Low-Voltage AC Series Arc Fault Detection

In a low-voltage electric distribution network, arc fault presents a high energy density electricity-discharging phenomenon between conductors, which is often caused by aging of electric facilities, loose contacts and terminals, or insulation failure due to internal and external destructions. A large amount of heat may be created during this discharging, which will further cause the risk of fire hazards to mitigate in the residential environment. Currently, many utility grid operators and electricity users are still devoted to seeking effective detection technology for arc fault protection. This paper proposes a hybrid approach that combines discrete wavelet transform (DWT), empirical mode decomposition (EMD), and dynamic time warping (DTW) methods for low-voltage AC series arc fault detection. In DWT, it uses time–frequency domain characteristics of the arc current signal to extract the occurrence of arc fault. In EMD, it decomposes the complex arc fault current signal into a finite intrinsic mode (IMF) signal; then, instantaneous amplitude of IMF signal is obtained by Hilbert–Huang transform (HHT) as a feature for arc fault identification. Firstly, the results of arc fault detections depend on the results from DWT and EMD. When both two methods detect different results, DTW method will be activated, using the similarity measurements between normal and arc fault current waveforms as an assistant measure to determine the occurrence of arc fault. The performance of the proposed approach is tested and validated using various electric appliances, and the results show that the proposed approach can effectively detect low-voltage AC series arc fault.

Probabilistic load forecasting for the low voltage network: Forecast fusion and daily peaks

Short-term forecasts of energy consumption are invaluable for the operation of energy systems, including low voltage electricity networks. However, network loads are challenging to predict when highly desegregated to small numbers of customers, which may be dominated by individual behaviours rather than the smooth profiles associated with aggregate consumption. Furthermore, distribution networks are challenged almost entirely by peak loads, and tasks such as scheduling storage and/or demand flexibility maybe be driven by predicted peak demand, a feature that is often poorly characterised by general-purpose forecasting methods. Here we propose an approach to predict the timing and level of daily peak demand, and a data fusion procedure for combining conventional and peak forecasts to produce a general-purpose probabilistic forecast with improved performance during peaks. The proposed approach is demonstrated using real smart meter data and a hypothetical low voltage network hierarchy comprising feeders, secondary and primary substations. Fusing state-of-the-art probabilistic load forecasts with peak forecasts is found to improve performance overall, particularly at smart-meter and feeder levels and during peak hours, where improvement in terms of CRPS exceeds 10%.

A method for determining arc breakdown in low-voltage electrical networks

In low voltage distribution networks, there is a high risk of fires caused by wiring faults that lead to short circuits. Arcing protection devices (ARCs) already exist, but experiments show that they also often do not disable such faults. The operation of most existing arc fault detection devices is based on the detection of high frequency current components and their comparison with load profiles. For the fast arc fault recognition low-frequency oscillations can be assessed, which serve as a marker of the arc fault presence in a LV distribution network. This method of arc fault recognition in LV networks is easier to implement practically. Using the windowed Fourier transform or Wavelet analysis, it is possible to determine the change in time of the harmonic components of the current, which will be a characteristic sign of the presence of an arc fault along with other signs.

Design and Simulation of Grid-Connected Photovoltaic Single-Phase Inverters

This paper focuses on a new control strategy for single-phase photovoltaic inverters connected to the electrical power distribution network. The inverter studied is single-phase H bridge, equipped with a robust control strategy by sinusoidal duty cycle modulation. This new control strategy offers the advantage over the control strategy. Most used control in its first approximation (PWM control technique): A low Hardware complexity; a variable modulation frequency/period; a topology of modulation with feedback. This inverter structure is further composed of the robust PI controllers, a boost chopper and an LCL filter. The low voltage electrical network to which this inverter is connected is materialized and simulated by a voltage source of characteristics 230V-15A-50Hz and synchronized to the latter by a phase-locked loop (PLL). In this article, the main components of the grid-connected PV power plant are modeled and simulated under Matlab/Simulink as well as the simulation of the global behavior of the entire network+PV inverter and the results obtained are presented.

CONSIDERATION OF THE CRITERION OF THE INFLUENCE OF ASYMMETRIC LOAD ON VOLTAGE DISTORTION IN A 10 kV NETWORK FOR RECOMMENDATIONS FOR REDUCING VOLTAGE ASYMMETRY

To date, there is a fairly large number of electrical equipment that is a source of asymmetric modes of operation in medium and low voltage electrical networks. This electrical equipment can create conductive low-frequency electromagnetic interference in electrical networks by the coefficient of voltage asymmetry in the reverse sequence. Studying the methodological basis of research on the theory of conductive low-frequency interference, it was found that when switching from one adjacent electrical network to another (for example, from a 0.4 kV network to a 10 kV network and vice versa) potential for conductive low-frequency interference decreases, i.e. the interference is partially suppressed by a certain amount. This amount is called the criterion determining the changes of the voltage asymmetry coefficient values in the reverse sequence in the transition of conductive low-frequency electromagnetic interference to the adjacent network. The purpose of this article is to develop a mathematical model for the study of network parameters affecting voltage asymmetry in the reverse sequence, which is reduced to a method for determining the value of the criterion for the effect of an asymmetric load on voltage distortion in a 10 kV network for recommendations for reducing voltage asymmetry. The article describes in detail the method of calculating this value and how it can be used to form recommendations for reducing voltage asymmetry. Scientific novelty of the study consists in the fact that an empirical mathematical model has been obtained that determines the criterion for the influence of an asymmetric load in a low-voltage network, the impact on which makes it possible to improve the electromagnetic situation in a 10 kV electrical network. This parameter can be taken into account when designing elements of electrical networks to determine the electromagnetic environment.

Planning of Low Voltage Electricity Distribution at Griya Arjuna Kejuden Housing

In a low-voltage power distribution system, there are often disturbances that result in disruption of electricity distribution to customers, resulting in losses for customers and PLN. The problem that often occurs is the occurrence of voltage drops and power losses so that in planning the construction of a low-voltage electric power distribution network, it is necessary to anticipate the occurrence of these problems. This research is expected to be used as a lesson for the creation of a low-voltage electric power distribution network with suitable and environmentally friendly construction and with low investment costs. collected data by visiting the location to conduct a survey and obtain accurate data related to the state of the research location. The stages in planning the Low Voltage Electricity Distribution Network begin with a field survey to obtain the required data. The installed power for each unit is 1.300 VA, so the total installed power is 122,200 VA and the spare power is 5% of the installed power so that the total installed power is 128.310 VA. during peak load times it is estimated that power consumption will only absorb 80% or 97,760VA. The required substation is a Portal Type Pole with a transformator capacity is 160kVA. The total breakdown of the electricity distribution network budget at the Griya Arjuna Kejuden is IDR 382,333,141.

The 0.38 kV electrical networks unbalancing operating modes optimization

The equipment 0.38 kV low-voltage electrical networks is not a satisfactory level. Such electric networks operating modes management is carrying out save energy measures and electricity supply improve efficiency in general largely allows. As a result, the electric energy supplied parameters obtaining actual nature information about to consumers through these electric networks is the developing the power transmission requirements measures basis comply. The article presents results current unbalancing modes objective studies in 0.38 kV an electrical network that feeds Irkutsk multi-storey residential building electric consumers. The analysis electric energy parameters, power quality indicators changes as well as electricity lo sses caused by the currents unbalance in the studied electric network are presented. The calculate parameters and using results of balancing device efficiency as well as its influence on the quality indicators studied and electrical energy loss in the studied electrical network are presented.

The 0.38 kV “Green Network” Operating Modes Simulation with Multi-Level Unbalanced Power Consumption

The article considers modeling, parameters calculation and analysis of the rural electric networks operating modes, containing power take-off units with multi-level unbalanced power consumption. At the same time, a low-voltage electrical network section fragment is considered as a certain cluster in the structure of an extensive and heterogeneous 0.38 kV network. The model is made for a certain “green network” cluster variant, containing several nodes of highly unbalancing power consumption with a balancing device (BD). Connecting options the BD in various power take-off nodes, including power supply buses, are considered. As a balancing technical means, a device is presented that has a minimum resistance to zero-sequence currents with its power automatically control in a zero-sequence currents function. The main criteria for assessing the currents and voltages unbalanced level are the zero-sequence voltage unbalance coefficient, which characterizes the power quality, as well as the power loss coefficient, which characterizes the increase in power and energy losses in the unbalanced mode. Based on the developed method, algorithm and computer program “Unbalance”, the calculation was made and the changes characteristics in the studied indicators were constructed using modern the Matlab graphics editor technologies. The analysis of the studied indicators was carried out, on the which basis the most appropriate node in the electrical network model was determined, where the functioning efficiency of the balancing device will be the greatest.

Green technologies use in the smart grid construction in rural power supply systems

The article considers the using intelligent controls possibility in low-voltage rural electric networks to minimize the unbalance modes consequences. The proposed technology includes the digital data transmission compilation on the electrical energy parameters with a new balancing technical means the electrical network operating mode. Digital feedback is provided for changes the balancing device (BD) parameters by the unbalancing power consumption changing level. Based on the developed methods compilation, software for calculating unbalancing modes has been created, which makes it possible to assess the currents and voltages unbalancing effect on the power quality and its additional losses change. The “green” technology proposed version, which increases the economic and the electric energy environmental safety use in the rural electric power industry, contains a new constructive solution for the balancing device implementation. The proposed technology was tested on the measurement data basis in existing electrical networks. Based on the MALAB technologies use, changes studied indicators visualization in the before and after BD integration in the electrical network was carried out and its analysis was makes. Used on the “neural networks” MALAB technology, a preventive assessment of the unbalancing power consumption events development in the investigated operating electrical network is presented, as well as the proposed technology effectiveness assessment was carried out.

Methods of Current Limitation in Low Voltage (up to 1 kV) Electric Networks

The article discusses and systematizes the causes of high values of short-circuit currents in electrical networks up to 1 kV and indicates their negative consequences. A brief analysis of some current limiting methods (both with and without additional investment) is given, which makes it possible to reduce the negative effects when significant short-circuit currents occur. The variants of the implementation of these current limiting methods recommended for study at the design stage or when replacing equipment that has exhausted its resource, are considered. The advantages and disadvantages of the methods of limiting short-circuit currents described in the article are indicated. Options for connecting equipment with low power consumption to nodes of the electrical network up to 1 kV with high values of short-circuit currents are also considered. Special attention is paid to current-limiting protection devices, a detailed description of the design of some of them is given, the advantages of their use in comparison with other current-limiting methods are indicated, the corresponding graphs of the limitation of the periodic component of the short-circuit current, shock short-circuit current and thermal pulse are presented. Based on the analysis of graphic materials, the issue of ensuring the selectivity of protections is considered. The degree of prevalence of equipment with the property of current limitation is determined. A method for determining selective current-limiting protection devices is given, viz. the method of energy selectivity, the corresponding graphs for determining energy selectivity are presented. The physics allowing to determine the degree of efficiency of limiting the short-circuit current is described. Recommendations on the use of current-limiting equipment are proposed.

Series FACTS controllers in industrial low voltage electrical distribution networks for reducing fault current levels

In this paper, series FACTS devices like Thyristor control series capacitor(TCSC)and Static synchronous series compensator (SSSC) with designed control logic used to reduce the fault current located in LV distribution network at the LV busbar. The electrical distribution network in small and medium scale industries such as steel plants, process and power plants is through low voltage switchgear (LVS) fed from motor control centre (MCC) switchgear through step down transformer of 11kV or 33kV /415V. The designed switchgear in the LV side for these utilities usually is at 50kA. However, the process loads are continuously increasing and sustained with additional feeders with the existing switchgear. Consequently, the fault current at the busbar of the switchgear increases which may require the replacement of entire switchgear to the new design fault current. However, upgrading the existing switchgear is not an economical solution to the industries. Alternatively reducing the fault current at the busbar is feasible. Controller design implemented for reducing the short circuit current with series FACTS devices. A study carried on 800 MW Thermal power plant Ash handling LVS in ETAP and Matlab. It is observed that the results are encouraging to use series FACTS devices effectively in the LVS.

Characterization and Modeling of LV Cables Considering External Parameters for Distribution Networks

In response to the climate emergency, new uses are plugged to low voltage (LV) electrical networks. The development of self-consumption complicates the LV grid operation, and force distribution system operators (DSOs) to better model and characterize their networks. DSOs mainly use a three-conductor model (3 CM) to compute power flows, and consider error margins of 2% for voltage profiles to reflect their model inaccuracy. The characteristics of the future LV grids call into question these margins, and the models used. In this paper, a four-conductor model (4 CM), and an additional model named 4 CMext, that considers external parameters (i.e., cable temperature, ground electrical resistivity, and value/number of the earthing resistances) are proposed. The best model for cable characterization and voltage profile calculation is chosen; the 4 CMext is more adapted for the characterization, and corresponds with the finite element model, with an error margin of 4%, experimental measurements of 15%, and French cable manufacturer data of 0.5%. For the voltage profile, the 4 CMext provides a more detailed view of the critical cases that could lead to a violation of the limits of the EN 50160 standard than 3 CM and 4 CM. Violations of high or low voltages are underestimated by two to six times by the 3 CM and 4 CM. Not considering external parameters can lead to a voltage profile error of above 3%. In this paper, we recommend that DSOs use the 4 CMext to represent LV networks, which would allow LV networks to be used closer to their physical limits, and avoid or postpone network reinforcements.

A Framework for the Resilience of LV Electrical Networks with Photovoltaic Power Injection

Context: Electrical distribution networks have undergone several changes in the last decade. Some changes include incorporating distributed energy sources, such as solar photovoltaic (PV) generation systems. It could modify the performance of the electrical network and leads to new challenges such as evaluating the impacts of the PV integration, the response to electrical and climatic disturbances, and the planning and restructuring of networks. Electrical network behavior versus PV integration could be evaluated by quantifying the variation in operation and including network resilience.
 Objective: Propose a reference framework to evaluate the resilience of LV electrical networks with PV power injection.
 Methodology: This paper addresses the framework for evaluating the performance of a low voltage (LV) electrical network in the face of the integration of PVs. It collects research related to evaluating the resilience of electrical networks on severe climate changes, natural disasters, and typical maneuvers. Then, it proposes a guideline to evaluate the performance of LV electrical networks with the integration of PV generation sources and includes resilience. For this, the determination of resilience evaluation indices is proposed. The indices are obtained from a normalized transformation of the measurable electrical parameters of the networks. The parameters are those that present the most affected by PV integration or are significant in the performance of the networks. Finally, it presents the evaluation of a proposed resilience index for a university building LV network as a case study.
 Results: The resilience assessment proposal is applied to a case study. When evaluating the resilience of the voltage at the common coupling point of the PV, an index of 0.84 is obtained, equivalent to 59.8 hours of overvoltage.
 Conclusions: It is possible to improve the resilience of the BT network through management strategies. In the case study, a 29% reduction in overvoltage hours was obtained by applying a curtailment strategy to the PV system.
 Financing: ECOS-Nord, Minciencias and Universidad Industrial de Santander.