kV Overhead Line Research Articles

Relationship between mains costs and voltage switches

The article deals with the issues of interconnection of network costs and power quality, in particular voltage deviations. The graphs of the distribution of voltage deviations for electrical receivers are given for two calculated load modes - the highest (100%) and the lowest (25%), corresponding to the choice of wires of 10 and 0.38 kV overhead lines for economic loads and voltage stabilization on 10 kV buses of 35/10 kV RTP at the level of + 5%.

IMPROVEMENT OF TECHNICAL AND ECONOMIC MODELS OF OVERHEAD LINES TRANSMISSION BASED ON CRITERIONAL METHOD

Improved technical and economic models of 35–750 kV overhead lines in accordance with the Law of Ukraine "On the Electricity Market" are proposed. The urgency and complexity of the problem is due to the fact that the transition to market relations presupposes the presence of private property, where the area under the grid facility, including the route of overhead lines, is a commodity and should be taken into account in shaping the value of this facility. In this regard, there is a need to review the discounted costs in the design of lines to bring them into line with market relations. The development of a new technical and economic model of 35–750 kV overhead lines was carried out taking into account the size and cost of land under the route of the line, which allows for a feasibility study of the optimal design option for the electrical network. The specific part of the land area in the cost of 1 km of overhead lines of different voltage classes is calculated. The components of the improved technical and economic model of 35–750 kV overhead lines are determined, namely the specific part of the component costs in the total cost of 1 km overhead lines of different voltage classes. A graphical representation of generalized models of investments in 35–750 kV overhead lines is presented. The presented studies take into account that during the construction of technical and economic models it is almost impossible to predict all its internal often stochastic connections, the elements of which cannot be expressed unambiguously, which leads to incomplete source information. Based on this fact, in the article for the analysis of the developed technical and economic models of lines the criterion method which allows to make decisions in conditional units both at full and at incomplete and indefinite initial information is applied. Implementing each equation of the developed technical and economic model of 35–750 kV overhead lines by the criterion method the ratio of components in the optimal design of lines in the corresponding voltage class is obtained, which allows to determine the development strategy of electrical networks and to form restrictions in incomplete source information.

Identification of the Mathematical Model of Failure Frequency of Overhead Lines of Power System Main Grid

Based on the analysis of accidents of 500 kV over-head lines of the main electric electrical grid of a wide region over a long-time-interval, the failure frequency (failure flux parameter) was determined under the influence of natural and socio-economic factors. It is proposed to consider the indicated failure rate as the output signal of a discrete positive dynamic system with many difficult formalizable inputs. To identify the mathematical model of a dynamic system, it is proposed to use the original method, the identifiability criterion of which is based on the compatibility condition of the linear matrix equation, and the numerical identification algorithm is based on the solution formula using zero-divisors and generalized inverse matrices. The method does not require a priori information about the parameters of the mathematical model of the electric electrical grid, does not involve solving the forecasting problem, and does not apply statistical calculations

Wire Break Protection System for 0.38 and 6 – 10 KV Overhead Power Transmission Lines

Currently, there is no automation and protection equipment to detect wire breaks in 6 – 10/0.38 kV electric networks. A protection system based on microprocessor electricity meters installed in a 0.38 kV network for the automatic detection of a damaged section of 0.38 and 6 – 10 kV overhead lines is proposed. A functional diagram of the protection system is described.

Types of overvoltages in 10-35 kV distribution networks and modern methods and means of their limitation

The basis for the transmission of electrical energy from sources to receivers are overhead power lines 10-35 kV. In these networks, an isolated transmission line or transmission line, grounded through resistors or using arc-quenching reactors, is used. The Republic of Mari El uses networks with isolated transmission line, the total length of which is more than 7000 km. When operating distribution networks, their insulation is affected by a number of internal factors such as long-term operating voltage and voltage fluctuations, short-term overvoltages associated with arc closures, wire breaks, and insulation overlaps. These networks are located on an open area, so they are exposed to lightning overvoltages, temperature, wind loads (mechanical forces), precipitation (snow, humidity). Overvoltages occurring in electrical systems are one of the main factors that significantly affect the reliability of power supply. Despite the short-term effects, overvoltages are characterized by a high multiplicity with respect to the long-term operating voltage, the impact on all electrically connected elements of the system, regardless of the place of occurrence. Overvoltage is the main cause of defects and accelerated aging of structural components. Currently, 90 % of 10-35 kV overhead lines are made on the basis of the use of reinforced concrete structures of supports that require grounding devices, depending on the value of the soil resistivity. Highspeed vacuum circuit breakers are used as switching devices in modern distribution networks of 10-35 kV. The specific properties of vacuum as an arc-quenching medium contribute to the transients in their switching, which require scientific understanding.

Analysis of the Condition and Monitoring of Emergency Power Outages in 10 kV Overhead Lines of the Oryol Region

Efficiency improvement of modern production is associated with uninterrupted power supply to consumers. Power supply reliability to consumers is ensured by reliable operation of power lines. The number of outages depends on their condition and operation quality. An increase in the number of outages affects the further degradation of power line state, significantly reducing the resource of lines and equipment; and it takes a lot of time to find faults and eliminate them. Monitoring of power outages in overhead power lines will reduce the time of emergency elimination.1

On reliability characteristics and service time limits of 500 kV overhead lines

The results are given of statistical analysis of the values of the failure rate (failure frequency) and its structure for overhead lines (OHL) 500 kV of the European part of the country over a long time period. The age structure of the 500 kV OHL is presented, according to which about 40% of the OHL have developed a normative service time of more than 50 years. It is shown, that an increase in the duration of the OHL operation from about 30 to 60 years leads to a doubling of their accident rate. The maximum possible service time period of 500 kV ОНL was estimated. For this purpose, instrumental surveys of the strength property of reinforced-concrete foundations and the degree of corrosive deterioration rate of 500 kV OHL steel transmission tower in three regions of the country were carried out: Vologda, Moscow and Volgograd regions. It is shown that the most critical element of 500 kV OHL affecting the service time limit is their transmission towers. Moreover, the degree of wear condition of the metal of the transmission towers depends on natural-climatic and man-made factors and decreases from the southern to the northern regions of the country. At the same time, the maximum possible service time limit of 500 OHL, put into operation in the middle of the last century, can be increased from 50 to 70-80 years. After that, the main structural elements of the 500 kV OHL should be completely replaced, which will be a large scientific and technical problem from the standpoint of reliability of the operating modes of the country’s united power system.

On chaotic state indications of time series of failure rate of overhead lines

The accident rate of 500 kV overhead lines (OHL) of a large region on a long time interval is researched. Significant fluctuations in the values of their failure rate (failure frequency) are revealed. The specified parameter was analyzed using the mathematical apparatus of the theory of deterministic (dynamic) chaos. The fractality of the time series of the OHL failure rate was revealed, as well as the positiveness of its maximal Lyapunov exponent, which indicated the chaotic nature of the dynamic process under consideration. The insignificant (less than five years) depth of forecasting the reliability characteristics of overhead lines due to the indicated chaotic state is substantiated. This is an unfavorable factor that reduces the reliability of the reliability estimates of the main grid of power systems.

Measurement-based frequency-dependent model of a HVDC transformer for electromagnetic transient studies

A wide-band, frequency-dependent five-terminal model is developed that represents one HVDC transformer unit in the French-English IFA2000 HVDC interconnection. Three such interconnected 1-ph units constitute one 3-ph transformer bank needed in 12-pulse conversion. The model is obtained via admittance frequency sweep measurements on the transformer's terminals, including common-mode measurements to capture the high-impedance coupling to earth at lower frequencies. The data set is modified to reduce the magnetizing current to a realistic level by a novel eigenvalue scaling procedure. The final data set is subjected to modeling by a stable and passive rational model while utilizing a mode-revealing transformation to retain the accuracy of the small eigenvalues that are related to the high-impedance coupling to earth. The paper describes details related to the measurements and modeling steps as well as the many intermediate accuracy validations that were done. Also is described challenges in the measurements that resulted due to interference of the measurements by a nearby 400 kV overhead line. The model is applied in a time domain simulation of the complete HVDC link in normal operation where voltage waveforms resulting from line commutations are compared against those by a classical model with added stray capacitances.

The effect of lightning impulse characteristics and line arrester to the lightning protection performance on 150 kV overhead lines: ATP-EMTP computational approach

This simulation study presents the effect of lightning strikes on the performance of arresters at 150 kV overhead lines. Lightning strikes have several parameters that affect the performance of line arresters (LA), namely lightning charge, and impulse energy. The simulation was attempted by injection of a direct strike to the ground wire with the peak voltage of 10 MV. The peak voltage was varied in terms of wavefront time (Tf) and the duration of lightning impulses (tau). In order to calculate current, charge and impulse energy of LA from various variations of Tf and tau, the trapezoidal numerical integration method is used. The current and impulse energy arising due to direct strikes and various variations of Tf and tau will be compared for each phase so that the influence of Tf and tau can be obtained from the performance of the LA and the current charge and impulse energy values are still within the limits of the IEEE C62.11 standard. The installation of LA and the position of arresters affected the peak voltage of lightning on the phase line when lightning struck it. The line arresters provide a drop in the peak voltage of lightning in phase lines. By installing line arresters in each tower, it will reduce the peak voltage of lightning on the phase line more significantly than the standalone line arrester. It is shown that the line arresters have to install at least six towers to reduce the peak voltage in the phase lines.

Exposure of adults to extremely low frequency magnetic field in France: results of the EXPERS study

Assessing the exposure of adults to magnetic field is a central point in the context of epidemiological studies. The EXPERS study is the first study at national scale in Europe with measurements of personal exposure to extremely low frequency magnetic fields, involving 1046 French adults with 24 h personal measurements. The proportion of adults with a 24 h AM of ≥ 1 µT was 2.1% for all adults and 0.3% for adults for which no alarm clock was identified, as this requirement of the measurement protocol was sometimes not respected. The alarm clocks were the main variable linked to the adults’ exposure measurements. The vicinity of the home to a high voltage power line increased the magnetic field exposure. However, only 1.7% of the adults were living close to a 63 to 400 kV overhead line, and only one of them had a personal exposure ≥ 1 μT with an AM of 1.1 μT. The exposure of adults was also correlated with some characteristics of the home and its environment, and some durations of activities, such as the duration of work and the duration in rail transport. The distribution of adults’ personal exposure was significantly different from the distribution of exposure during sleep, and from the distribution of exposure assessed from measurements during sleep and work. This highlights the complexity of the exposure assessment in epidemiological studies.

Health Assessment and Prediction of Overhead Line Based on Health Index

Overhead lines are important parts of distribution networks at present. Assessment and prediction of their health status is of great significance to ensure the reliable operation of distribution network. This paper presents a method for assessing and predicting the health status of overhead lines based on health index (HI). First, the key features set of overhead lines including ontological and nonontological factors is determined. Then, a calculation method for evaluating HI based on analytic hierarchy process and technique for order preference by similarity to an ideal solution is proposed. Subsequently, the health assessment results of the actual 110 and 10 kV overhead lines located in China show that the proposed method could reflect the actual situation of overhead lines well. Finally, based on the proposed method, this paper takes two areas of China, Beijing and Nanjing, which have different climatic conditions, as research objects, and studies the influence of natural factors on the health status of overhead lines, respectively. Based on the analysis results, the health statuses of the overhead lines in the two regions are predicted. The research results of this paper can provide guidance for the operation and maintenance of overhead lines.

OPTIMIZATION OF DESIGN PARAMETERS OF AUTOTRANSFORMERS IN ICE MELTING SCHEME WITH NON-INDUCTIVE CIRCUIT ON 6-10 KV OVERHEAD POWER LINES

Purpose. The purpose of the paper is to determine the basic electrical characteristics and to develop a calculation method and algorithm for optimizing the design parameters of autotransformers intended for use in a melting ice scheme with a non-inductive circuit on 6-10 kV overhead power lines. Methodology. The development of the technical and economic model and the method for calculation of the design parameters of the autotransformer for melting ice is performed on the basis of a systematic approach. Optimization of structural characteristics of autotransformers is carried out using a combined algorithm based on the spatial grid method, adapted to the case of a mixed space of discrete and continuous independent variables, and the specifics of the technical and economic model of the autotransformer. The proposed combined optimization algorithm is implemented in the Delphi environment. Results. Based on the required specific melting power, the main electrical characteristics of autotransformers intended for use in the melting ice scheme with a non-inductive circuit on 6-10 kV overhead lines, which were the basis for optimizing their design parameters, have been calculated. The technical and economical model of autotransformer for melting ice, which is defined by nine independent variables and describes its cost and technical parameters, is developed. On the basis of the obtained electrical characteristics, optimization of the design parameters of a series of autotransformers is carried out, which includes three standard sizes, differing in maximum length of the transmission line. Originality. A method of calculation of structural parameters of autotransformers for ice melting is proposed, the peculiarity of which is the use of the criterion of the minimum of the cost of the active part and taking into account the conditioned by the circuit of connection of the autotransformers the technical restrictions of errors on the value and angle of secondary current, which are important from the point of view of ensuring the permissible deviation of the specific power of melting ice. Practical value. Optimal correlations of geometrical sizes and electromagnetic loads of autotransformers for ice melting, their cost indicators, as well as the main design characteristics of the magnetic circuit and windings are established. Results of design calculation of autotransformers are sufficient for introduction of their serial production in industrial conditions.

Use of Machine Learning in the Analysis of Indoor ELF MF Exposure in Children.

Characterization of children exposure to extremely low frequency (ELF) magnetic fields is an important issue because of the possible correlation of leukemia onset with ELF exposure. Cluster analysis—a Machine Learning approach—was applied on personal exposure measurements from 977 children in France to characterize real-life ELF exposure scenarios. Electric networks near the child’s home or school were considered as environmental factors characterizing the exposure scenarios. The following clusters were identified: children with the highest exposure living 120–200 m from 225 kV/400 kV overhead lines; children with mid-to-high exposure living 70–100 m from 63 kV/150 kV overhead lines; children with mid-to-low exposure living 40 m from 400 V/20 kV substations and underground networks; children with the lowest exposure and the lowest number of electric networks in the vicinity. 63–225 kV underground networks within 20 m and 400 V/20 kV overhead lines within 40 m played a marginal role in differentiating exposure clusters. Cluster analysis is a viable approach to discovering variables best characterizing the exposure scenarios and thus it might be potentially useful to better tailor epidemiological studies. The present study did not assess the impact of indoor sources of exposure, which should be addressed in a further study.

Analiza możliwości poprawy niezawodności napowietrznej linii 15 kV narażonej na katastrofalne oblodzenie w warunkach polskich

The paper is a result of a synergic cooperation of two academic teams, i.e. power engineering and mechanical teams, and a distribution system operator. A real 15 kV overhead line exposed to a catastrophic load of ice and rime was analyzed and three solutions to improve the reliability of the tested object in such conditions were examined. Authors considered: shortening the length of the line spans, heating the main line with increased current and rebuilding the overhead line to a cable line. The researches worked out a FEM model taking into account the newest normatives, simulated the model, experimentally increased the load on the real line with measured wire temperature, and performed multi-variant calculations to determine indicators of reliability, i.e. SAIDI and SAIFI. The analyses were followed by conclusions thanks to which the reliability of power lines exposed to catastrophic icing could be increased. These inferences should be considered and applied by all distribution system operators in Poland.

Feasibility study on the use of oil-well tubing in construction of intermediate support for 6-10 kV high voltage overhead power lines in the development of oilfields

This article is devoted to assessing the technical effectiveness and economic feasibility of oilwell tubing in construction of intermediate supports for overhead power lines (6–10 kV) in the development of oil, gas and condensate field in the conditions of Far North. The article considers the technical possibility and economic feasibility of using the built-up cross section of the intermediate support of overhead lines consisting of two tubes welded together. The SCAD office software was used to calculate the strength of the proposed section for the design load, taking into account the impact of climatic factors. A comparative analysis of the construction cost was performed for 1 km of overhead power lines made of conventional materials and oil-well tubing. The calculations showed the feasibility of using this material for the construction of 6-10 kV overhead lines.

Еще раз о цикличности аварий в основных сетях энергосистем

The recurrence of failures of 500 kV overhead lines in a vast region on an extended time interval is investigated. An essential scatter of their flaw rate (failure frequency) values under the effect of natural and social-economic factors has been revealed. The failure frequency wavelet spectra were plotted, from which a few historical failure rate periods have been revealed. It is proposed to consider the flaw rate as the output signal of a dynamic system containing a multitude of poorly formalized inputs. This parameter is determined by multifactorial and poorly formalized summation of the effects caused by the environment and by social-economic relations. The stability of this dynamic system has been estimated. Ways for formalizing the multidimensional dynamic model of failure rate in the grid backbone networks have been outlined.

About accidents cyclicality and mathematical model of failure rate in main electrical grids of power systems

The accidents cyclicality of 500 kVoverhead lines of a large region over an extended time period was studied. Significant fluctuations in the values of their failure rate (failure frequency) under the impact of natural and socio-economic factors are revealed. The wavelet spectrums of the failure frequency were constructed, which revealed several historical periods of accidences. It is proposed to consider the failure rate as the output signal of a dynamic system with many difficultly formalized inputs. The stability of this dynamic system is evaluated. The ways of formalizing a multidimensional dynamic model of accidence in main electrical grids of power systems are outlined.

The Mutual Influence of Signals from the Location Monitoring Equipment and Technological Communication in the High-Frequency Path of Power Transmission Line

The paper describes the main characteristics of equipment used for technological communication by means of overhead electric transmission lines: high-frequency relay protection, command transmission of emergency control, high-frequency communication for the transmission of telemechanics and telephony signals, as well as equipment for a location equipment for monitoring the condition of electric transmission lines. The results of experimental studies on the mutual influence of the signals from the location monitoring equipment and technological communication in the high-frequency path of overhead transmission lines are presented. It shows a lack of effect of signals from location monitoring equipment on the work of technological communication equipment. Methods are proposed to reduce the influence of technological communication signals on the operation of location equipment: the method of signal accumulation and the method of digital filtering of signals. Analysis of the results of joint operation of the location monitoring equipment and high-frequency communication equipment under various conditions and operating modes on operating 35-330 kV overhead lines confirms their full compatibility.

Development of software and hardware complex of operative diagnostics of structural part of 35-220 kV overhead lines operated in Northern regions of Western Siberia

The article is devoted to the problems of maintenance of overhead power lines in the Far North of Western Siberia. For improvement of quality and reliability of power supply of consumers in the conditions of the Far North of Western Siberia, decrease in operational costs and volumes of the carried-out emergency works the hardware-software complex for expeditious inspection, assessment and forecasting of change of technical condition of constructive part of air lines (VL) of 35-220 kV is developed, the structure of the hardware-software complex of registration of the condition of constructive part of VL of 35-220 kV and structure of the hardware-software complex of storage., processing and analysis of the obtained data on the States of the constructive part of the VL 35-220 kV.