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Numerous uncertainties exist in various electricity power system problems due to the size, complexity, geographical distribution, and influence of unforeseen events in these systems, making it difficult for traditional mathematics tools based on crisp set theory to have an impact on and solve many power system problems. As a new branch of mathematical uncertainty techniques, the neutrosophic expert systems approach has therefore emerged with the development of electric power systems and has proven successful when correctly linked. The expert typically uses ambiguous or neutrosophic language to describe their empirical knowledge, such as "very likely," "quite likely," "if x is large, then y is very likely to occur," "x should not be less than a," etc. To design an optimal radius of power supply in the electrical transformer substation, this article presents a new method for creating primal and dual neutrosophic geometric programming problems. It also provides a numerical example to evaluate the approximate optimal economic power supply radius. [ABSTRACT FROM AUTHOR]

World trends in the use of underground space in the construction of modern cities were studied. It is shown that the underground space can be used for the needs of a modern city, in particular for the construction of commercial objects, trade and household institutions, entertainment, cultural and educational, sports facilities, transport networks. A wellplanned and properly operated underground infrastructure improves the quality of life, energy efficiency and environmental safety to a greater extent than a similar system on the surface. At the same time, due to the placement of part of the urban infrastructure underground, the area of greenery increases and the environmental condition of large cities and their historical centers improves. Examples of the development and rational use of the underground space of cities in Canada and other countries are analyzed, the possibility of obtaining a developed network of civil defense protective structures, equipped with all the necessary communications for people’s stay, is shown, which has become especially relevant in modern war conditions. The global experience of the construction of underground transformer stations is summarized and the prospects for the implementation of the underground construction of such facilities in Ukraine are shown. The basic problems of modern urban construction include the shortage of urban areas, the accumulation of vehicles on the roads, the lack of parking spaces, the inability of the urban infrastructure to cope with the ever-increasing load, and the deterioration of the ecological situation. Changes are shown regarding the growth of energy supply to consumers from 3 to 5 kW, and the introduction of a new player on the Ukrainian electricity market - an energy storage facility operator. Placing up to 20…25 % of urban infrastructure underground allows to reduce the energy consumption of the housing stock. In the conditions of Ukraine’s refusal to import natural gas and the transition to electric heating, mainly at the expense of RES, new residential buildings will lead to a decrease in the amount of greenhouse gas emissions, and a part of the territories of cities for greening will increase, since vegetation is a significant conservator of carbon dioxide. The underground location of transformer substations in Ukraine is substantiated and proposed for the first time, which will ensure the achievement and solution of a number of problems of modern urban planning. [ABSTRACT FROM AUTHOR]

The construction of transformer substations in transmission lines is a systematic, technical, and complex project with the need for numerous materials and resources. Under the development of the green economy, the requirements for energy conservation and carbon reduction have improved; hence, an assessment of carbon emissions in transformer substations is urgently needed. A calculation method was proposed in the present study to analyze the carbon emissions of transformer substations with different kinds of data sources, which were collected from several practical projects in the west-to-east power transmission project. In this study, a detailed comparison and discussion regarding the differences in carbon emissions of 750 kV transformer substations caused by hydrology, geology, engineering quantity, and other factors were conducted. The mean value, standard deviation, and 90% confidence interval of carbon emissions were obtained by Monte Carlo simulation through MATLAB. Results show that the total carbon emissions of the selected 750 kV transformer substations are between [56,000, 68,000] t CO2 eq. Construction engineering accounts for more than 50% of carbon emissions, followed by installation engineering and additional services. In terms of input items, electricity distribution buildings contribute more than 39% of total carbon emissions, followed by cable/earthing systems, which account for 14% of total carbon emissions. Gas insulated switchgear (GIS) and air insulated switchgear (AIS) could adopt different types of equipment foundations, and GIS equipment foundations would generate fewer carbon emissions due to the smaller land area and input materials. This study can provide experience and reference for similar projects and further guide the substation carbon emission reduction work. [ABSTRACT FROM AUTHOR]

The construction of transformer substations in transmission lines is a systematic, technical, and complex project with the need for numerous materials and resources. Under the development of the green economy, the requirements for energy conservation and carbon reduction have improved; hence, an assessment of carbon emissions in transformer substations is urgently needed. A calculation method was proposed in the present study to analyze the carbon emissions of transformer substations with different kinds of data sources, which were collected from several practical projects in the west-to-east power transmission project. In this study, a detailed comparison and discussion regarding the differences in carbon emissions of 750 kV transformer substations caused by hydrology, geology, engineering quantity, and other factors were conducted. The mean value, standard deviation, and 90% confidence interval of carbon emissions were obtained by Monte Carlo simulation through MATLAB. Results show that the total carbon emissions of the selected 750 kV transformer substations are between [56,000, 68,000] t CO2 eq. Construction engineering accounts for more than 50% of carbon emissions, followed by installation engineering and additional services. In terms of input items, electricity distribution buildings contribute more than 39% of total carbon emissions, followed by cable/earthing systems, which account for 14% of total carbon emissions. Gas insulated switchgear (GIS) and air insulated switchgear (AIS) could adopt different types of equipment foundations, and GIS equipment foundations would generate fewer carbon emissions due to the smaller land area and input materials. This study can provide experience and reference for similar projects and further guide the substation carbon emission reduction work.

Determining an economical and reliable spare transformer strategy is an essential and challenging task for power utility companies. This study proposes a probabilistic cost‐benefit analysis‐based spare transformer strategy incorporating condition monitoring information. Not only the actual wearing condition of each transformer, but also the impacts of a transformer ageing process on spare transformer strategy are considered by the proposed method. First, the actual wearing condition and functional age of each transformer are estimated based on condition monitoring information. Secondly, the ageing process and ageing failure rate of each transformer are modelled by combining a Weibull distribution and its functional age. Thirdly, based on probabilistic cost‐benefit analysis, the outage costs, as well as economic benefits under different inventory sizes, are estimated. The transformer's ageing process is modelled and considered in the determination of the optimal number and the acquisition timing of spare transformers. Finally, a transformer substation group and its condition monitoring information, and the real spare transformer strategy collected from a regional power grid in China were used to demonstrate an application of the proposed method. The results indicate that the spare transformer strategy determined by the proposed method not only enables the power utilities to avoid economic losses but also guarantees a high cost‐benefit ratio of spare transformer strategy. [ABSTRACT FROM AUTHOR]

Due to the high UHV AC/DC transmission line tower, the working voltage amplitude on the wire is large, causing lightning accidents. The paper first analyses the impact of lightning strike point on lightning overvoltage of 1000 kV UHV transformer substation and determines the research object of lightning intruding wave overvoltage. Second, the influence of the impact grounding resistance of transformer side lightning arrester and transmission line tower on invaded wave is analysed. Finally, the commutation failure of HVDC system was analysed, and the simulation tests were carried out by CIGER standard model in PSCAD and Simulink, valve voltage and valve current waveform can be used as a new basis for judgment. The conclusion shows that the analysis of UHV AC/DC hybrid system commutation failure should start from the DC system to study, and commutation failure directly related to the failure, operating conditions, and other factors.

The capacitance isolation device is a kind of effective suppression of DC bias in transformers caused by HVDC monopolar operation. However, according to the actual operation of the system, the capacitive isolation device at the neutral point of a transformer will probably cause more serious DC bias in other adjacent transformers while inhibiting its internal bias current at the same time. Since autotransformers are applied widely in the high-voltage network, in this paper, we considered the structural characteristics of it and introduced the concept of effective bias current to describe the influence of magnetic bias current on the transformer more accurately. Then, the authors choose the bias current at any substations in the target grid less than the limit value as the constraint condition. Aiming at the minimum number of installed capacitors, the genetic algorithm based on improved niche is used to solve the optimal configuration problem. Taking the Ethiopia power grid as a test case, the authors work out the optimal quantity and installed location of capacitance isolation devices which satisfy the constraint condition. Compared with the traditional method, the cost is greatly reduced.

The capacitance isolation device is a kind of effective suppression of DC bias in transformers caused by HVDC monopolar operation. However, according to the actual operation of the system, the capacitive isolation device at the neutral point of a transformer will probably cause more serious DC bias in other adjacent transformers while inhibiting its internal bias current at the same time. Since autotransformers are applied widely in the high-voltage network, in this paper, we considered the structural characteristics of it and introduced the concept of effective bias current to describe the influence of magnetic bias current on the transformer more accurately. Then, the authors choose the bias current at any substations in the target grid less than the limit value as the constraint condition. Aiming at the minimum number of installed capacitors, the genetic algorithm based on improved niche is used to solve the optimal configuration problem. Taking the Ethiopia power grid as a test case, the authors work out the optimal quantity and installed location of capacitance isolation devices which satisfy the constraint condition. Compared with the traditional method, the cost is greatly reduced. [ABSTRACT FROM AUTHOR]

Due to the high UHV AC/DC transmission line tower, the working voltage amplitude on the wire is large, causing lightning accidents. The paper first analyses the impact of lightning strike point on lightning overvoltage of 1000 kV UHV transformer substation and determines the research object of lightning intruding wave overvoltage. Second, the influence of the impact grounding resistance of transformer side lightning arrester and transmission line tower on invaded wave is analysed. Finally, the commutation failure of HVDC system was analysed, and the simulation tests were carried out by CIGER standard model in PSCAD and Simulink, valve voltage and valve current waveform can be used as a new basis for judgment. The conclusion shows that the analysis of UHV AC/DC hybrid system commutation failure should start from the DC system to study, and commutation failure directly related to the failure, operating conditions, and other factors. [ABSTRACT FROM AUTHOR]

Distribution Asset Management is an important task performed by utility companies to prolong the lifetime of the critical distribution assets and to accordingly ensure grid reliability by preventing unplanned outages. This study focuses on microgrid applications for distribution asset management as a viable and less expensive alternative to traditional utility practices in this area. A microgrid is as an emerging distribution technology that encompasses a variety of distribution technologies including distributed generation, demand response, and energy storage. Moreover, the substation transformer, as the most critical component in a distribution grid, is selected as the component of the choice for asset management studies. The resulting model is a microgrid-based distribution transformer asset management model in which microgrid exchanged power with the utility grid is reshaped in such a way that the distribution transformer lifetime is maximised. Numerical simulations on a test utility-owned microgrid demonstrate the effectiveness of the proposed model to reshape the loading of the distribution transformer at the point of interconnection in order to increase its lifetime.

This study describes the development and evaluation of a compact system for onsite calibration of 1000 kV voltage transformers in ultra‐high‐voltage (UHV) AC power transmission projects. The proposed compact system consists of a 1000 kV electromagnetic voltage transformer as a standard, a high‐voltage resonant power supply, and a voltage transformer test set, which are assembled and mounted on a calibration truck. The developed system accuracy is 0.05% in ratio and 0.058 mrad in phase angle, respectively. Also, the total basic uncertainty is about ±0.028% and ±0.03 mrad under field conditions. The compact system can be automatically set up and taken down quickly on site requiring no substation cranes or utility operating crews. It has successfully undergone complete field tests and calibrated 63 1000 kV voltage transformers in total at 5 UHV substations. The feasibility of an automatic and efficient approach to calibrating UHV voltage transformers on site has been demonstrated. [ABSTRACT FROM AUTHOR]

Nowadays, a strong concern to decrease greenhouse gas emissions is encouraging the implementation of renewable energy sources closer to end‐users, in low‐voltage (LV) distribution networks. Due to the expected high microgeneration (µG) penetration level, several problems are likely to arise, such as overvoltages and reverse power flow. This study presents a review of the several techniques used to deal with these problems. These are compared in terms of their capacity to smooth the voltage profile and avoid reverse power flow. An unbalanced three‐phase power flow algorithm, based on current summation method for radial distribution networks, is proposed. A study based on a highly unbalanced test radial LV distribution network for a typical summer day, with a high µG penetration, is performed. The voltage profile, active power flow in the service transformer, and power losses on the network are the monitored electrical quantities. The obtained results indicate that self‐consumption with storage is the recommended solution to eliminate overvoltages, to avoid reverse power flow and allow for a decreasing in the power losses. Nevertheless, the economic viability of this solution must be carefully assessed, because the profitability of the project is not straightforward at the current time. [ABSTRACT FROM AUTHOR]

The transformer losses can usually be classified into two basic categories: losses in the transformer core (voltage‐dependent losses) and losses in the transformer winding copper (current‐dependent losses). By increasing the number of active transformers in the transformer substation the authors reduce the total losses in the transformer copper but on the other hand increase the total losses in the transformer iron core. Considering this, it can be concluded that it is possible to determine the optimum number of active transformers in the substation for each operating condition together with the way they are connected. In this study, the authors propose a novel optimisation algorithm which can be used to determine the optimal operating conditions of the transformer substation to minimise annual energy losses while avoiding frequent transformer switching and assuring provision of sufficient transformation power in order to supply distribution load. The algorithms which are outlined are applicable for substations 110/x kV and 35/10(20) kV which have more than one transformer installed with different levels of substation topology complexity (flexibility). [ABSTRACT FROM AUTHOR]

Since failure of high‐ to medium‐voltage (MV) transformers affect a large number of consumers, they are usually built with a redundancy to guarantee service restoration in the case of a single contingency. The redundancy can be provided by a backup transformer or by transferring the load to a neighbouring substation in case of failure. While a load transfer allows for more efficient use of transformers in normal operation, it also requires the MV network to be dimensioned with redundant transmission capability for the contingency case. In this study, the authors present their approach to determine if it is profitable in the long term to remove a backup transformer in intrinsically safe substations and handle resupply with load transfer to neighbouring substations instead. To this end, they compare the cost of the necessary network expansion to the costs of a backup transformer. They introduce an iterated local search algorithm for the calculation of emergency switching plans as well as expansion of the MV network. The methodology is applied to a large real MV network group, where reinforcing the network to allow a load transfer is cost efficient compared with the existing backup transformer in three of four substations. [ABSTRACT FROM AUTHOR]

In this study, a digital realisation of the IEC (International Electrotechnical Committee) flickermeter using root mean square (RMS) of the voltage waveform as its input, instead of the voltage waveform, is presented. The aim of this research work is to compute the flicker severity according to the IEC flickermeter standard, IEC 61000‐4‐15, when only the RMS values of the voltage waveform are available. Hence, a new method is proposed to compute the light flicker directly from half‐cycle‐RMS values of the voltage, which are computed based on the IEC power quality standard, IEC 61000‐4‐30. Beginning from the signal model for a voltage with flicker provided in IEC 61000‐4‐15, the RMS of the voltage waveform is derived in terms of the flicker frequency components and the corresponding amplitudes. It has been shown on simulation data that short‐term flicker severity can be computed by the proposed method with an average error rate of 0.021%. The method has also been applied on field data collected at a transformer substation supplying an electric arc furnace plant, and has been shown to successfully generate flicker severity from RMS voltage waveforms, when compared with the IEC flickermeter results. [ABSTRACT FROM AUTHOR]

The main reasons for installation of power quality meters in distribution transformer substations are power quality monitoring and global evolution of electrical network towards the 'smart grid'. In case that all measurements from the meters are properly synchronised and centralised, new possibilities of control or evaluation of the network are enabled. This contribution proposes the possibility for an earth fault localisation with the aid of synchronised data recorded on the low‐voltage side of the medium voltage/low voltage transformers in compensated neutral distribution networks which are equipped with auxiliary resistor for short‐time increasing of the active part of the fault current. The described method uses voltage sags evoked by connecting of the auxiliary resistor for locating the faulty section. The proposed method is tested with the help of numerical model which presents a part of the distribution network. [ABSTRACT FROM AUTHOR]

This paper deals with coupling transformer core saturation problem in cascaded multilevel converter (CMC) based transmission-type static synchronous compensator (T-STATCOM) systems. The effects of nonlinear characteristics of the coupling transformer and CMCs on the core saturation phenomenon are investigated, and the associated mechanisms are described. In order to prevent the transformer core from being saturated, dc current components in the coupling transformer secondary lines are eliminated by modulating one or more than one voltage steps of staircase CMC voltage waveforms via the electronic gating circuitry. The proposed dc current elimination method is implemented on a 154-kV, ±50-MVAr CMC-based T-STATCOM system, which is operating either in interarea oscillation damping or terminal voltage regulation modes at any time in a 400/154-kV transformer substation since March 2010. The effectiveness of recommended dc current elimination method is verified in the field. [ABSTRACT FROM AUTHOR]

The fault current limiting transformer (FCLT) presented by J. Brochu et al. (see IEEE Trans. Power Delivery, vol.13, p.233-40, 1998) was designed with the purpose of increasing the total capacity of a transformer station without increasing short-circuit currents. In situations where such an IPC is closely coupled with parallel transformers, the FCLT installation can be simplified. The purpose of this letter is to describe the enhanced capabilities and outline the basic design criteria for this innovative IPC application. An application example provides typical component ratings, space requirements, and a budget cost estimate [ABSTRACT FROM PUBLISHER]