scholarly journals Operation Modes of HV/MV Substations

2009 ◽  
Vol 25 (25) ◽  
pp. 81-86
Author(s):  
Josifs Survilo ◽  
Antons Kutjuns
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Warm Season ◽  
Electrical Energy ◽  
Cold Season ◽  
Power Losses ◽  
Medium Voltage ◽  
The Third ◽  
Operation Modes ◽  
Mode 3

Operation Modes of HV/MV SubstationsA distribution network consists of high voltage grid, medium voltage grid, and low voltage grid. Medium voltage grid is connected to high voltage grid via substations with HV/MV transformers. The substation may contain one, mostly two but sometimes even more transformers. Out of reliability and expenditure considerations the two transformer option prevail over others mentioned. For two transformer substation, there may be made choice out of several operation modes: 1) two (small) transformers, with rated power each over 0.7 of maximum substation load, permanently in operation; 2) one (big) transformer, with rated power over maximum substation load, permanently in operation and small transformer in constant cold reserve; 3) big transformer in operation in cold season, small transformer-in warm one. Considering transformer load losses and no load losses and observing transformer loading factor β it can be said that the mode 1) is less advantageous. The least power losses has the mode 3). There may be singled out yet three extra modes of two transformer substations: 4) two big transformers in permanent operation; 5) one big transformer permanently in operation and one such transformer in cold reserve; 6) two small transformers in operation in cold season of the year, in warm season-one small transformer on duty. At present mostly two transformers of equal power each are installed on substations and in operation is one of them, hence extra mode 5). When one transformer becomes faulty, it can be changed for smaller one and the third operation mode can be practiced. Extra mode 4) is unpractical in all aspects. The mode 6) has greater losses than the mode 3) and is not considered in detail. To prove the advantage of the third mode in sense of power losses, the notion of effective utilization time of power losses was introduced and it was proven that relative value of this quantity diminishes with loading factor β. The use of advantageous substation option would make it possible to save notable amount of electrical energy but smaller transformer lifetime of this option must be taken into account as well.

Conversion of Electrical Energy in the Processes of Its Generation and Transmission

2010 ◽  
pp. 208-230
Keyword(s):  
Power Plant ◽  
High Voltage ◽  
Nuclear Power ◽  
Low Voltage ◽  
Thermal Power ◽  
Electrical Energy ◽  
Hydro Power ◽  
Medium Voltage ◽  
Electrical Generator ◽  
Burning Coal

Electrical energy can be obtained by burning coal (thermal power plant), by using nuclear fuel (nuclear power plant) or by using the power of water (hydro power plant). In these cases, the energy obtained by the sources put a shaft of an electrical generator in motion. The generator generates electrical energy – see Figure 1. In the installation, excitation system for the generator is used. The system turns on an uncontrolled rectifier, thyristor-controlled rectifier or AC thyristor regulator dependent on the generator type. The obtained energy is transmitted using a transmission system towards consumers. The transmission yet is made mainly in high-voltage AC energy form (HVAC). In different parts of the transmission network the voltage value may be different. There are so-called high-voltage (420 kV, 220 kV, 110 kV, etc) and medium voltage (20 kV, 6.6 kV, etc.) systems. General consumers consume electrical energy from so-called low-voltage systems (230V, 50Hz or 110V, 60Hz). During the transmission the type of energy does not change, only the value of the voltage changes using transformers.

Reduction of the Low Voltage Substation Constraints by Inserting Photovoltaic Systems in Underserved Areas

2019 ◽  
Vol 12 (2) ◽  
pp. 105-112
Author(s):  
Benbouza Naima ◽  
Benfarhi Louiza ◽  
Azoui Boubekeur
Keyword(s):  
Low Voltage ◽  
Voltage Drop ◽  
Electrical Energy ◽  
Utilization Rate ◽  
Photovoltaic Systems ◽  
Voltage Distribution ◽  
Medium Voltage ◽  
Pv Systems ◽  
Transformer Substation ◽  
Load Pattern

Background: The improvement of the voltage in power lines and the respect of the low voltage distribution transformer substations constraints (Transformer utilization rate and Voltage drop) are possible by several means: reinforcement of conductor sections, installation of new MV / LV substations (Medium Voltage (MV), Low Voltage (LV)), etc. Methods: Connection of mini-photovoltaic systems (PV) to the network, or to consumers in underserved areas, is a well-adopted solution to solve the problem of voltage drop and lighten the substation transformer, and at the same time provide clean electrical energy. PV systems can therefore contribute to this solution since they produce energy at the deficit site. Results: This paper presents the improvement of transformer substation constraints, supplying an end of low voltage electrical line, by inserting photovoltaic systems at underserved subscribers. Conclusion: This study is applied to a typical load pattern, specified to the consumers region.

scholarly journals The third form electric organ discharge of electric eels

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Xu ◽  
Xiang Cui ◽  
Huiyuan Zhang
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
The Third ◽  
Electric Organs ◽  
Electric Eel ◽  
New Finding ◽  
Discharge Behavior ◽  
Unique Species

AbstractThe electric eel is a unique species that has evolved three electric organs. Since the 1950s, electric eels have generally been assumed to use these three organs to generate two forms of electric organ discharge (EOD): high-voltage EOD for predation and defense and low-voltage EOD for electrolocation and communication. However, why electric eels evolved three electric organs to generate two forms of EOD and how these three organs work together to generate these two forms of EOD have not been clear until now. Here, we present the third form of independent EOD of electric eels: middle-voltage EOD. We suggest that every form of EOD is generated by one electric organ independently and reveal the typical discharge order of the three electric organs. We also discuss hybrid EODs, which are combinations of these three independent EODs. This new finding indicates that the electric eel discharge behavior and physiology and the evolutionary purpose of the three electric organs are more complex than previously assumed. The purpose of the middle-voltage EOD still requires clarification.

scholarly journals Calculations, norming and reducing of electrical energy losses in city electrical networks

2019 ◽  
Vol 21 (3) ◽  
pp. 46-54
Author(s):  
A. V. Lykin ◽  
E. A. Utkin
Keyword(s):  
High Voltage ◽  
Power Transmission ◽  
Low Voltage ◽  
Demand Curve ◽  
Electrical Energy ◽  
Electrical Network ◽  
Energy Losses ◽  
Capital Investments ◽  
Electrical Networks

The article considers the feasibility of changing the structure of a distribution electrical network by transferring points of electricity transformation as close to consumers as possible. This approach is based on installation of pole-mounted transformer substations (PMTS) near consumer groups and changes the topology of the electrical network. At the same time, for groups of consumers, the configuration of sections of the low-voltage network, including service drops, changes. The efficiency of approaching transformer substations to consumers was estimated by the reduction in electrical energy losses due to the expansion of the high-voltage network. The calculation of electrical losses was carried out according to twenty-four hour consumer demand curve. To estimate the power losses in each section of the electrical network of high and low voltage, the calculated expressions were obtained. For the considered example, the electrical energy losses in the whole network with a modified topology is reduced by about two times, while in a high-voltage network with the same transmitted power, the losses are reduced to a practically insignificant level, and in installed PMTS transformers they increase mainly due to the rise in total idle losses. The payback period of additional capital investments in option with modified topology will be significantly greater if payback is assessed only by saving losses cost. Consequently, the determination of the feasibility of applying this approach should be carried out taking into account such factors as increasing the reliability of electricity supply, improving the quality of electricity, and increasing the power transmission capacity of the main part of electrical network.

Selecting the Switching Frequency of the 6500 V IGBT High Voltage DC Converter

2021 ◽  
pp. 21-27
Author(s):  
Sergey I. Volskiy ◽  
◽  
Yuri Yu. SKOROKHOD ◽  
Nikolay Echkilev ◽  
◽  
...  
Keyword(s):  
High Voltage ◽  
High Frequency ◽  
Electrical Energy ◽  
Input Voltage ◽  
Switching Frequency ◽  
Energy Transformation ◽  
Power Losses ◽  
Voltage Converter ◽  
Passenger Cars ◽  
Power Circuit

The high-voltage converter with the input voltage of 3000 V DC is considered for use as a power supply for auxiliary circuits of commuter electric trains and passenger cars that are used on Russian railways. The limitations on the use of semiconductor devices in converters with an input voltage of 3000 V are shown. The power electrical circuits of the input units of the considered high-voltage converters are shown when using of 1700 and 6500 V IGBT. The expressions for calculating the power losses and the algorithm for selecting the switching frequency of 6500 in IGBT are given. This article is of interest to developers of high-voltage DC converters with an input voltage of 3000 V and higher, which choose IGBT for the power circuit of input units with using the high frequency principle of the electrical energy transformation.

Idejno rešenje regionalnog Data Centra kod Beograda napajanog iz obnovljivih izvora energije

2021 ◽  
Vol 23 (3) ◽  
pp. 10-17
Author(s):  
Ivan Vujović ◽  
Željko Đurišić ◽  
Keyword(s):  
High Voltage ◽  
Power Supply ◽  
Wind Farm ◽  
Low Voltage ◽  
Power Transformer ◽  
Renewable Energy Sources ◽  
Geographical Location ◽  
Electrical Energy ◽  
Economic Benefits ◽  
Infrastructure Development

Telecommunications and computer equipment centralisation trends for the purpose of achieving economic benefits, usage of technological innovations and new technical solutions implementation leads to the requirements for building bigger Data Centres (DCs). An increase in the size of the DC facility i.e. the number of racks inside occupied with equipment and the number of devices that enables the proper functioning of that equipment leads to necessarily power energy requirements increasing for power supply. For the DCs that require a large amount of energy, the building of their own, usually renewable energy sources (RES) is cost-effective. In such a caser, RES are primary and Power System (PS) is secondary and redundant power source. A concept of a DC primary powered from RES is presented in this paper. Generated electrical energy in RES is transmitted in PS through high voltage switch-gears (SGs) while DC is power supplied from PS through low voltage, medium voltage and high voltage SG-s. For the purpose of realisation of such facility, it is necessary to enable adequate conditions related to geographical location, physical access to the facility, possibility of connecting to the PS and possibility of connecting to the telecommunications centres. Based on carried out researches related to RESs potential, available roads, power supply infrastructure and telecommunication infrastructure, development conditions for DC on location near to Belgrade, close to power transformer station „Belgrade 20“ are analysed in this paper. From the aspect of DC power supply, proposed solution includes wind farm, solar plant and landfill gas power plant, as well as related SGs. Telecommunication connections from DC to the PS and other important telecommunication centres are provided. These connections are realised through optical cables placed next to the electrical lines and cables, and, when that is not possible, placed independently in the ground. The design of the DC interior is given and calculations of the required electrical energy for the power supply of the equipment and devices in the facility are performed. Based on calculation results, capacity calculation of the RES and calculation of SGs are performed. Design of the interior optical connections inside DC is also given. A General assessment of the investment and economics of building such DC are given at the end of the paper.

scholarly journals Novel Enhanced Modular Multilevel Converter for High-Voltage Direct Current Transmission Systems

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2257
Author(s):  
Dimitrios Vozikis ◽  
Fahad Alsokhiry ◽  
Grain Philip Adam ◽  
Yusuf Al-Turki
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Medium Voltage ◽  
High Voltage Direct Current ◽  
Current Transmission ◽  
The Cost ◽  
Voltage Harmonics ◽  
Chain Links

This paper proposes an enhanced modular multilevel converter as an alternative to the conventional half-bridge modular multilevel converter that employs a reduced number of medium-voltage cells, with the aim of improving waveforms quality in its AC and DC sides. Each enhanced modular multilevel converter arm consists of high-voltage and low-voltage chain-links. The enhanced modular multilevel converter uses the high-voltage chain-links based on medium-voltage half-bridge cells to synthesize the fundamental voltage using nearest level modulation. Although the low-voltage chain-links filter out the voltage harmonics from the voltage generated by the high-voltage chain-links, which are rough and stepped approximations of the fundamental voltage, the enhanced modular multilevel converter uses the nested multilevel concept to dramatically increase the number of voltage levels per phase compared to half-bridge modular multilevel converter. The aforementioned improvements are achieved at the cost of a small increase in semiconductor losses. Detailed simulations conducted in EMPT-RV and experimental results confirm the validity of the proposed converter.

Benefits of High Voltage SiC Applications in Medium Voltage Power Distribution Grids

2018 ◽  
Vol 924 ◽  
pp. 875-878 ◽  
Author(s):  
Shi Qi Ji ◽  
Xiao Jie Shi ◽  
Zhe Yu Zhang ◽  
Wen Chao Cao ◽  
Fred Wang
Keyword(s):  
High Voltage ◽  
Power Distribution ◽  
Low Voltage ◽  
System Stability ◽  
System Level ◽  
Medium Voltage ◽  
Low Voltage Ride Through ◽  
Grid Interface ◽  
Potential Benefits ◽  
Distribution Grids

This paper evaluates potential benefits of high voltage (HV) SiC devices in medium voltage (MV) distribution grids. The MV microgrid, that HV SiC devices can benefit most, is selected as the “killer application” and focused in this paper. The design and simulation are carried out to compare Si-and SiC-based grid interface converters for the quantitative benefit assessment both at converter level and system level. The SiC-based converter has significant benefits in weight and size, and shows enhanced performance and functionality on power quality, system stability and low voltage ride through (LVRT) as well.

scholarly journals Analysis of the Electricity Supply Contracts for Medium-Voltage Apartments in the Republic of Korea

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 293
Author(s):  
Dong Sik Kim ◽  
Wookyung Jung ◽  
Beom Jin Chung
Keyword(s):  
High Voltage ◽  
Electrical Energy ◽  
Republic Of Korea ◽  
Supply Contracts ◽  
Medium Voltage ◽  
Apartment Complex ◽  
The Common ◽  
Energy Consumptions ◽  
The Republic ◽  
Apartment Complexes

For apartment complexes receiving medium-voltage electrical energies, the apartments can choose an electricity charging method between the single and general contracts in the Republic of Korea. In the single contract, a residential high-voltage rate is applied to the total electrical energy consumptions of households and common areas. On the other hand, in the general contract, different rate plans are applied to the electrical energy consumptions of households and their common areas, where a generic high-voltage rate plan is applied to the common consumption. Hence, depending on the amounts and composition of the consumptions, both contracts have their own strengths and weaknesses in terms of the total electricity charge. The management office of an apartment complex can select its preferred contract considering the amount and composition of the power consumptions on an annual basis. In this paper, we first formulate a model for the contracts and analyze their properties based on Monte-Carlo simulations. We then observe the contract properties through actual metering data from 30 apartment complexes in Korea. From the analysis of this paper, we can select appropriate contract for a given apartment complex and have guidelines for saving electricity charges. The greater the consumption of the electrical energy and the common area portion, the more advantageous the general contract is in terms of reducing electricity charges.

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