Selecting a Grounding Scheme for Screens of Power Cable Lines

Load currents and short-circuit currents in high-voltage power cable lines are sources of the induced voltages in the power cables’ concentric metallic sheaths. When power cables operate with single-point bonding, which is the simplest bonding arrangement, these induced voltages may introduce an electric shock hazard or may lead to damage of the cables’ outer non-metallic sheaths at the unearthed end of the power cable line. To avoid these aforementioned hazards, both-ends bonding of metallic sheaths is implemented but, unfortunately, it leads to increased power losses in the power cable line, due to the currents circulating through the sheaths. A remedy for the circulating currents is cross bonding—the most advanced bonding solution. Each solution has advantages and disadvantages. In practice, the decision referred to its selection should be preceded by a wide analysis. This paper presents a case study of the induced sheath voltages in a specific 110 kV power cable line. This power cable line is a specific one, due to the relatively low level of transferred power, much lower than the one resulting from the current-carrying capacity of the cables. In such a line, the induced voltages in normal operating conditions are on a very low level. Thus, no electric shock hazard exists and for this reason, the simplest arrangement—single-point bonding—was initially recommended at the project stage. However, a more advanced computer-based investigation has shown that in the case of the short-circuit conditions, induced voltages for this arrangement are at an unacceptably high level and risk of the outer non-metallic sheaths damage occurs. Moreover, the induced voltages during short circuits are unacceptable in some sections of the cable line even for both-ends bonding and cross bonding. The computer simulations enable to propose a simple practical solution for limiting these voltages. Recommended configurations of this power cable line—from the point of view of the induced sheath voltages and power losses—are indicated.

. It is noted that at present, 10 and 35 kV overhead power transmission lines are being laid outside the settlements of the Republic of Belarus on reinforced concrete vibrated (10 kV) and centrifuged (35 kV) poles that are characterized by low reliability and damaging the environment (on account of alienation of land for poles, the need to make a wide clearing for laying in the forest, obstructions by poles and wires of lines to the operation of agricultural machinery, the danger of electric shock to personnel and the public). It is possible to avoid these disadvantages if, instead of overhead lines, power transmission cables with cables insulated by cross-linked polyethylene are used which are characterized by a very low failure flow parameter. Contrary to the prevailing opinion about the higher cost of cable power transmission lines compared to overhead ones of the same rated voltage, it turned out that, taking into account reliability, the cost of electricity lost in the lines for a year, damage to the environment and to the power system caused by the need to perform more expensive emergency repairs (as compared to a planned one), laying cable lines with three-core and single-core cables of a voltage of 10 and 35 kV instead of overhead cables outside the populated area is fairly justified. In this connection, the laying of three-core cables is more preferable. It should be also borne in mind that with an increase in the length of cable lines, the capacitive earth fault current increases, to compensate for which additional devices are needed to be installed in power centers, viz. arc-extinguishing reactors or resistors, accounting for the cost of which (up to 22 % of the cost of one kilometer of cable line) does not significantly affect the conclusions we have drawn regarding the effectiveness of using 6–35 kV cable power lines in an unpopulated area instead of overhead ones, however.

Исследован процесс ослабления магнитного поля (МП) высоковольтной кабельной линий (КЛ) из одножильных кабелей при двухстороннем заземлении их экранов. Разработана методика численного моделирования и расчета МП КЛ
\nна основе метода конечных элементов с применением осесиммеричной расчетной модели КЛ, что позволило описать
\nусловие замыкания экранов кабелей на концах КЛ и решить задачу в двумерной постановке. Получены точные и экспериментально обоснованные значения коэффициентов ослабления МП КЛ при двустороннем заземлении экранов в
\nзависимости от технических характеристик кабелей и геометрии их укладки.

The aim of this work is to study the effect of a signal induced by an external electromagnetic field on the quality of electricity transmitted over a cable line. The article presents the results of developing a mathematical model of the effect of external electromagnetic fields on cable lines. To check the obtained results was realized a simulation model of interaction between alternating electromagnetic field and cable lines, based on the finite element method, and created using PC FEMM, which allowed us to obtain a graphical representation of the distribution of intensities of electric and magnetic fields in the cable AASw 3×240 under the influence of external fields generated by overhead power line with rated voltage of 110 kV. An algorithm is developed for determining possible deviations of the voltage in the cable line from the rated voltage depending on the amplitude characteristics of the incident wave. The resulting estimate of the effectiveness of shielding cables brand AASw.

Power system steady state and transient analysis require correct modeling of overhead transmission lines and cables operating at 110–750 kV. The key difficulties to model sections of overhead and cable lines are caused by complex conductor geometry, their transposition, as well as grounding schemes of ground wires of overhead lines and screens of underground cables. The paper covers various aspects of 110–750 overhead line and cable modeling that must be taken into consideration to obtain a reliable mathematical model in a phase domain. Modern software does not provide a universal solution to determine line parameters. The 110–500 kV cable line modeling issues have not been worked out properly and require careful analysis of specialized foreign literature. Thus, the task to develop the algorithms of calculating the parameters of overhead and cable power lines is relevant, taking into account the various configuration options of these lines which are possible in operational practice. To derive overhead transmission line and cable line models, electric circuit theory and matrix algebra methods have been used. The ATP/ATPDraw and MATLAB/Simulink software environment has been used to investigate what tools are available to determine line parameters, as well as to verify some of the calculation results. Analysis has been carried out to reveal the options available in the ATP/ATPDraw and MATLAB/Simulink software to compute line parameters in a phase domain. An algorithm has been developed and verified to calculate overhead line parameters regardless of the number of parallel circuits. The key features of the calculation of the matrix of linear resistances of overhead power transmission lines are outlined. The main features of modern cable lines operating at 110–500 kV are also described. The paper presents various cable layouts possible in real-field conditions, as well as provides expressions that allow obtaining correct impedances and admittances for a system of cable line conductors. Study of the options of various software tools dedicated to overhead line parameter calculation in a phase domain has revealed that these tools cannot be deemed universal to represent an overhead line of whatever configuration. However, the developed algorithm is universal as it allows computing line parameters regardless the ground wire grounding approach. The expressions presented in this paper consider various layouts of 110–500 kV cable lines that could be encountered in the Russian power system.

RELEVANCE. The length and complexity of the geography of medium voltage cable lines is at a high level. Such lines extend underground, on supports in the air. In order to constantly maintain the reliability of city power supply at a high level, any interruptions and accidents should be promptly corrected.TARGET. The main goal of the work is to develop the theory of medium voltage CL research, to practically and theoretically substantiate the search for the most convenient and effective installation for CL diagnostics, to study and develop possible modifications of CL diagnostic installations.METHODS. A variant of CL diagnostics based on the CPDA-60 installation is proposed, which makes it possible to find and localize the places where defects occur in the insulation based on the measurement and analysis of partial discharges (PD). Suitable for insulation monitoring in all types of high voltage cables. The CPDA installation can be used when testing new cable lines being put into operation, and to analyze the condition of old cables in operation.RESULTS. Cable lines require an integrated approach to diagnostics and monitoring, since the reliability of modern authentication systems for the generation and distribution of electricity is largely determined by the electrical reliability of electrical equipment. Technical diagnostics of equipment is a key link, the quality of which determines the efficiency of the processes of organizing production activities, strategic planning and renovation of electric grid assets.CONCLUSION. The study and analysis of the presented data and research allows us to form a conclusion regarding the method of measuring and localizing partial discharges (PD) in power cable lines (CL) using the Online Wire Testing System (OWTS) diagnostic system. The OWTS system allows real-time measurements without interrupting cable lines, making it especially valuable to the energy industry. Thanks to the introduction of advanced technologies and signal processing algorithms, the method has high accuracy and sensitivity to minimal manifestations of private discharges, which allows not only to detect, but also to accurately localize the location of defects in the insulation. The use of this method can significantly increase the service life of power cables, reduce the likelihood of sudden accidents and, as a result, reduce the cost of repair and maintenance of electrical power equipment. Ultimately, improvements in diagnostic and monitoring techniques, including the method of measuring and localizing PD in power lines using OWTS, represent a significant step towards improving the reliability and safety of electrical power systems. This will not only reduce operating costs, but also ensure uninterrupted and high-quality power supply to consumers.

Locating the partial discharge (PD) source is one of the most effective means to locate local defects in power cable lines. The sampling rate and the frequency-dependent characteristic of phase velocity have an obvious influence on localization accuracy based on the times of arrival (TOA) evaluation algorithm. In this paper, we present a cross-correlation algorithm based on propagation distance to locate the PD source in cable lines. First, we introduce the basic principle of the cross-correlation function of propagation distance. Then we verify the proposed method through a computer simulation model and investigate the influences of propagation distance, sampling rate, and noise on localization accuracy. Finally, we perform PD location experiments on two 250 m 10 kV XLPE power cables using the oscillation wave test system. The simulation and experiment results indicate that compared with traditional TOA evaluation methods, the proposed method has superior locating precision.

The knowledge of the statistical distribution of the overvoltages stressing the insulation of a cable line is fundamental for the insulation coordination. The estimation of such distributions requires the utilization of complex numerical programs. In this paper a simplified method which takes into account a typical configuration in a power system "overhead line - cable line - transformer" is introduced. The results, although in a general form, highlight that the knowledge of an overvoltage reduction factor, estimated once for all for different cables and power system configurations, can be used to evaluate in an easy way the distribution of the overvoltages stressing the insulation of a cable line starting from the statistical distribution of the overvoltages impinging the cable line.

Operation faults of HV power cable lines have been increasing because of multi-points grounding of cable sheath which caused by over voltage breakdown. Cable metallic shield grounding and over voltage protecting techniques have been noticeably along with more and more underground power cable lines applied in urban transmission and distribution system. It is the key for us to design and optimize the technical parameters of over voltage protector used for single-core power cable metallic shield grounding and over voltage protecting. But neither international nor national standards have defined the rules of how to choose the parameters until today. In this paper, the rules and methods of design and optimization of over voltage protector for cable metallic shield grounding and over voltage protecting were discussed based on national standards of China such as GB 50217 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">code</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">for</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">design</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">of</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cables</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">of</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">electric</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">work</i> , DL/T401 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">guide</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">to</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">the</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">selection</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">of</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">high</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">voltage</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cables</i> and DL/T5221 Technical Rule for Design of Urban Power Cables as well as practical experience of long-term operation of power cable lines. Furthermore, lightning impulse test and large impulse current test were used for validating reliability and preponderance of the protector design in the paper. The results of theory analysis and tests proved that the over voltage protector for cable metallic shield grounding and over voltage protecting designed by the rules can satisfy the technical requirements of the standards and meet the practical demands of power cable lines operating safely and reliably.

In the present paper, the comparison results of two main kinds of the power lines are presented, namely, overhead lines and cable lines. The analysis was done in the low-voltage mains network in the frequencies identified by the CENELEC organization for a narrowband transmission using low-cost PLC modems. The currently data transmission with the use of the PLC technique finds increasing use in the area of the communication for the Smart Grid, especially because of Smart Metering and Smart Lighting systems development. Independently form the implementation of the PLC transmission technique, a process of replacement of overhead lines with cable ones is carried out. Undoubtedly this process must have an influence on the transmission prosperities over the mains network. This paper is aimed to show differences in the secondary transmission parameter of the two main constructional types of low-voltage lines, which have the same electro-power parameter. The influence of these differences on the transmission quality is also discussed. The study has been limited to aluminium and copper wires and was made in the low-voltage mains network.

In the current global economic crisis and acute shortage of energy resources, increasing importance is attached to energy saving measures, economical and careful consumption of raw materials, materials, electricity and heat, environmental safety of industrial production. During the reconstruction of existing power supply systems of industrial enterprises, modern progressive solutions should be considered and implemented, morally and physically obsolete electrical equipment should be replaced, namely the introduction of new electrical equipment for transition from 6/10 kV to 20 kV in Ukrainian power systems. It is also necessary to pay attention to the improvement of power supply circuits and distribution networks, the implementation of complex automation of complex technological processes, rational compensation of reactive power at all levels of power supply systems. In the power system, the main transport link is the power line. Power lines (transmission lines) are long conductors suspended at a safe distance from the ground overhead lines (overhead lines) or cable lines (overhead lines) in which conductors are insulated from each other and from the environment and protected by insulation and armor electricity. Power lines are the most massive elements of the power supply system, they connect the individual nodes of its circuit. Longitudinal and transverse parameters are distinguished in alternative schemes. The load current flows through the longitudinal parameters, voltage is applied to the transverse ones. The replacement circuit of the electrical network consists of replacement circuits of the following elements: power lines, transformers, reactors, capacitors, loads, power sources. Calculating the steady-state modes of power systems, the substitution schemes of the elements are given in a single-line design, because the parameters of all phases are symmetrical. In local and local electrical networks with a relatively short length and low rated voltage, the conduction currents are small compared to load currents. Therefore, in typical electrical calculations of these networks, the capacitive conductivity of the lines is not taken into account. However, for these networks, the accounting of capacitive conductivities is necessary when considering some modes, the existence of which in itself is due only to the presence of capacitive conductivities. For example, the mode of single-phase ground fault in a network with isolated or compensated neutral or analysis of the modes of operation of neutrals of electrical networks of different voltage classes cannot be performed without taking into account the capacitive conductivity of these networks. When switching the power system of Ukraine to the nominal voltage of 20 kV, it should be taken into account that the transmission line will be replaced in the sections of both the overhead power line and cable power line, namely 35, 10, 6 kV. The replacement scheme must describe all the characteristics and properties of the elements of cable and overhead lines in accordance with real conditions. Thus, it is not expedient to use simplified substitution circuits that neglect energy parameters and properties of conductors to study the parameters of transmission lines. The use of a complete "P" -shaped scheme for the analysis of the parameters of transmission lines and transmission lines for a voltage of 20 kV is the basis of mathematical modeling of the transmission system in the distribution networks of our country.

nd power cable lines with various options for the mutual arrangement of conductors using a probing system based on magnetically sensitive probes. The probing system is located on the micro-tunnel-boring shield and is designed to detect power cable lines on or near the working path, directly during tunneling operations. The change in the topology of the magnetic field created by the active power cable line with different configurations of the mutual arrangement of its conductors is numerically studied. The paper also contains the exploration of the electromagnetic field weakening at a distance of advanced probing (3-3.5 meters from the cable line) due to the lay of conductors with current, as well as by placing the cable line in a reinforced concrete cable tray. The dependences for the magnetic induction values in the soil and the body of the tunnel shield on the configuration of the cable line conductors are obtained, and the possibility of detecting this induction is also determined.

현재 국내에서 사용되고 있는 22.9[㎸]-y 배전 방식은 지중 케이블로 전력을 공급하고 있으며, 선로 운영상 배전 케이블 선로의 동심중성선을 케이블 접속 구간마다 3선 일괄 접지하는 3상 일괄 다중접지방식을 채택하고 있다. 이 방식에서는 동심중성선에 부하 전류의 약 40[%](전력구)~50[%](관로)의 동심중성선 순환 전류가 발생하고 있다. 본 논문은 이와 같은 문제점을 해결하기 위하여 새로운 3상 비일괄 동심중성선 다중접지방식을 제안하고 있으며, 케이블의 허용전류계산, 케이블차폐층의 유기전압 및 선로에서 발생하는 유도장애등의 기술적인 문제들을 종합적으로 해석하고 있다.

The review concerning application of fiber-optic technologies in power industry, in particular, for monitoring of modern power cables with cross-linked polyethylene insulation and integrated fiber-optic module is carried out. The new intelligent tools for control of electrical, thermal and mechanical characteristics and partial discharges in power cable lines are presented. The current operational experience for the system of Smart Cable Guard in an emergency is described. The prospects to develop and use the intellectual technologies for monitoring of technical state of up-to-date high-voltage cable power lines and their operate reliability are grounded by analysis of new diagnostic methods controlling the level of partial discharges, temperature distribution and mechanical damage in polyethylene insulation and other elements of the high- and extra-high-voltage cables with integrated fiber-optic modules. References 51, figures 8.

The results of experimental measurements of currents and voltages in the elements of cable power lines and communication lines at occurrence of single-phase short-circuit of power cable lines 110 and 220 kV are present. The effect of the short circuits on the operation of the communication cable lines that are laid in the same trench with power cables is evaluated. Explanations to the emerging effects and recommendations for practical use of the results obtained in design, operation and repair of cable lines are given.