1,667 research outputs found

    Power quality and electromagnetic compatibility: special report, session 2

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    The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

    Impact of intergrating teebus hydro power on the unbalanced distribution MV network

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    Small hydro power sources have been identified as one of the renewable energy technologies that the South African government is focusing on in order to generate more electricity from renewable/independent resources. Due to the low carbon output of most renewable energy technologies and the carbon intensive power generation technologies that are currently being used in South Africa e.g. Hydro, coal, gas, and etc. further pressure is increasing to incorporate cleaner forms of generation. In 2002 a study focusing on the hydropower potential was compiled providing an assessment according to conventional and unconventional possibilities for all the provinces. Nowadays, the power electricity demand is growing fast and one of the main tasks for power engineers is to generate electricity from renewable energy sources to overcome this increase in the energy consumption and at the same time reduce environmental impact of power generation. Eskom Distribution Eastern Cape Operating Unit (ECOU) was requested to investigate the feasibility of connecting a small hydro power scheme located in the Teebus area in the Eastern Cape. The Eastern Cape in particular, was identified as potentially the most productive area for small hydroelectric development in South Africa for both the grid connected and off grid applications. These network conditions are in contrast to the South African electricity network where long radial feeders with low X/R ratios and high resistance, spanning large geographic areas, give rise to low voltages on the network. Practical simulation networks have been used to test the conditions set out in the South African Grid Code/NERSA standard and to test the impact of connecting small hydro generation onto the unbalanced distribution network. These networks are representative of various real case scenarios of the South African distribution network. Most of the findings from the simulations were consistent with what was expected when comparing with other literatures. From the simulation results it was seen that the performance of the variable speed generators were superior to that of the fixed speed generators during transient conditions. It was also seen that the weakness of the network had a negative effect on the stability of the system. It is also noted that the stability studies are a necessity when connecting the generators to a network and that each case should be reviewed individually. The fundamental cause of voltage instability is identified as incapability of combined distribution and generation system to meet excessive load demand in either real power or reactive power form

    Comparison of methods for calculating parameters of a power supply system

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    This paper discusses two methods for calculating the parameters of a power supply system – paper based approach (PBA) and computer based approach (CBA). We study the load data of the metallurgical plant. PBA and CBA results are modeled in the ETAP software program. The output data from this program are the power losses in the transformer-line section and the voltage level after the transformers. These output data are needed for estimating the energy and economic efficiency based on the two approaches. Using power losses, the energy losses are found. Energy losses and equipment cost are used in the economic analysis of projects by NPV criterion. This paper can help to understand whether there is a significant difference in energy and economic efficiency following from the PBA and CBA results, and also how to improve and update the PBA.This paper discusses two methods for calculating the parameters of a power supply system – paper based approach (PBA) and computer based approach (CBA). We study the load data of the metallurgical plant. PBA and CBA results are modeled in the ETAP software program. The output data from this program are the power losses in the transformer-line section and the voltage level after the transformers. These output data are needed for estimating the energy and economic efficiency based on the two approaches. Using power losses, the energy losses are found. Energy losses and equipment cost are used in the economic analysis of projects by NPV criterion. This paper can help to understand whether there is a significant difference in energy and economic efficiency following from the PBA and CBA results, and also how to improve and update the PBA

    Electrical assessment of georeferenced distribution network due to electric vehicles deployment

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    En la actualidad la sociedad está enfocada en la mitigación del daño ambiental basado en la integración de energía renovable y vehículos eléctricos en las redes eléctricas. Energías limpias como energía solar y eólica en la generación de electricidad están destinadas a reemplazar los derivados de combustible fósil, mientras que los vehículos eléctricos substituyen a los vehículos de combustión interna. En este contexto, el presente proyecto propone un análisis a una red eléctrica real georreferenciada considerando los principales retos que involucran la conexión de cargas no lineales al sistema eléctrico. El modelo utiliza información georreferenciada de los usuarios y la red eléctrica existente, donde corrientes desbalanceadas consumidas por los usuarios son evaluadas basado en modelos de carga para clientes residenciales y comerciales. El impacto debido a la inclusión de vehículos eléctricos es desarrollado en el software PowerFactory mediante análisis de flujos de potencia, análisis de amónicos y desbalance de voltajes.Several cities worldwide are focused to reduce the environmental degradation based on the deployment and integration of renewable energies and electric vehicles (EV) into the distribution network. The first one replaces electricity produced by fossil fuels with solar, wind or hydro power plants, whilst the second one is a feasible alternative to substitute internal combustion engine (ICE) vehicles with eco-friendly vehicles. Set in this context, this paper proposes an examination about the main effects in a georeferenced distribution system when non-linear loads are connected to the grid. The distribution network model contemplates georeferenced data from customers, where unbalanced currents due to the customer’s consumption in each distribution transformer is evaluated using a variety of coefficient for commercial and residential load models. Voltage unbalance, harmonics and load flow analysis is performed in PowerFactory to determine the impacts of EVs to the grid

    Distribution network development planning with quality of supply (QOS) costing

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    Includes bibliographical references.The report outlines details of research in distribution network development with consideration of costs due to quality. Network planning methods are diverse with the common objective of establishing minimum cost options without violating network constraints. The selected network alternative is directed to meet customer requirements. Network planning models have evolved from consideration of simplistic models to multi variable and more realistic approaches. It is not always possible to achieve the desired outcome because planning is a difficult and complex task. There are usually uncertainties due to vague or no information available about the long-term (15-20 years) planning. The uncertainties generally result in risks, which have to be sufficiently analysed before reaching planning decisions. The recently proposed Minimum Risk Criterion is not a preferred risk resolution approach because it suggests that utilities should not establish expensive networks due to cost risk. Uncertainty modeling approaches based on fuzzy logic are proposed as the solution for analysis of uncertain conditions where very limited information is available. Costs in distribution lines are usually due to capital investment and operating costs. Distribution capital costs are primarily due to cost of conductor, s ucture and insulator. The cost of conductor and structure varies with size and type. Insulator costs do not vary significantly with variations in insulator type and properties. Quality related costs are a relatively new concept in distribution costing and are developed in the research. They are primarily due to mitigation, condition monitoring and interruptions. Quality mitigation costs are defined in the mitigation cost models in Figure 4- 8 and Figure 4- 9. The impact cost values in the models were established on the basis of assumptions, which require further research. According to CTLab [12], quality-monitoring equipment costs could vary from R50, 000 to R250, 000. Interruption costs are incurred through penalty cost and revenue losses. The penalty cost is similar to the revenue loss cost in many respects but is incurred when the standard limits are violated. Revenue loss costs are applicable whenever the frequency or voltage deviates from the nominal. It may be preferred to accept revenue losses where mitigation is expensive

    Concepts for design of an energy management system incorporating dispersed storage and generation

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    New forms of generation based on renewable resources must be managed as part of existing power systems in order to be utilized with maximum effectiveness. Many of these generators are by their very nature dispersed or small, so that they will be connected to the distribution part of the power system. This situation poses new questions of control and protection, and the intermittent nature of some of the energy sources poses problems of scheduling and dispatch. Under the assumption that the general objectives of energy management will remain unchanged, the impact of dispersed storage and generation on some of the specific functions of power system control and its hardware are discussed

    Electricity Distribution Networks: Investment and Regulation, and Uncertain Demand

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    Electricity distribution networks are capital intensive systems and timely investments are crucial for long-term reliability of their service. In coming years, in the UK, and elsewhere in Europe, many networks are in need of extensive investments in their aging assets. Also, aspects of energy policy concerning climate change, renewable energy, energy efficiency, demand side management (DSM), network energy loss reduction, quality of service standards, and security of supply require active, flexible, and smart networks that can be achieved through investments. This paper is a chapter in the forthcoming book "Jamasb T. and Pollitt, M. G. (2011) Eds., The Future of Electricity Demand: Customers, Citizens and Loads, Cambridge University Press: Cambridge" and describes a network investment assessment model developed as a tool to identify and assess the investment requirements of distribution networks. A broadening of the scope of network investments to include demand-related measures that can reduce the need for investments

    Analysis of Large Scale PV Systems with Energy Storage to a Utility Grid

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    With electric distribution network operators experiencing an exponential increase in distributed energy resource connections to the power grid, operational challenges arise attributable to the traditional methods of building distribution feeders. Photovoltaic (PV) solar systems are the major contributor due to recent technological advancements. Though this renewable energy resource is beneficial to human society, unfavorable electrical conditions can arise from the inherit variability of solar energy. Extreme variability of power injection can force excessive operations of voltage regulation equipment and potentially degrade customer voltage quality. If managed and controlled properly, battery energy storage systems installed on a distribution feeder have the ability to compliment solar generation and dampen the negative effects of solar generation. Now that customers are connecting their own generation, the traditional design assumption of load flowing from substation to customer is nullified. This research aims first to capture the maximum amount of generation that can be connected to a distribution feeder. Numerous deployments of generation scenarios are applied on six unique distribution feeders to conclude that hosting capacity is dependent on interconnect location. Then, existing controllers installed on voltage regulation equipment are modeled in detail. High resolution time series analysis driven from historical measurements is conducted on two contrasting feeders with specific PV generator deployments. With the proper modeling of on-load tap changer controls, excessive operations caused by extreme PV generation swings were captured. Several services that battery energy storage systems can provide when connected to an individual distribution feeder with significant PV generation include long term absorption of excessive PV generation, dynamic response to extreme PV generation ramping, and release of stored energy for system peak shaving. A centralized master energy coordinator is proposed with the ability to dispatch the battery system in such a fashion to implement each service throughout consecutive days of operation. This solution was built by integrating load and solar energy forecasting predictions in order to construct an optimum charging and discharging schedule that would maximize the asset’s lifespan. Multiple load and solar generation scenarios including a consecutive three day run is included to verify the robustness of this energy coordinator
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