High-voltage Cable Lines Research Articles

Retraction Note: Applications of artificial intelligence and hybrid neural network methods with new bonding method to prevent electroshock risk and insulation faults in high-voltage underground cable lines

Retraction Note: Applications of artificial intelligence and hybrid neural network methods with new bonding method to prevent electroshock risk and insulation faults in high-voltage underground cable lines

Effective metal shields of high voltage distribution cable lines

<p>The presented methodology enables determining induced currents and voltages relevant to the correct estimation of security conditions required in operating and maintenance of the metal installations surrounding high-voltage distribution cable lines. It is based on the on-site measurements of currents appearing in two phase conductors of the considered cable line during a simulated ground fault in the supplied substation. Their values are utilized to compensate for the deficiency of all relevant but unknown data concerning the surrounding metal installations. It was done by introducing an equivalent cable shield substituting, from the standpoint of inductive influence, all surrounding metal installations. Here is shown that this equivalent shield can be determined in such a way that it becomes identical from the standpoint of its appearance to the actual cable line shield but with a changed value of its longitudinal resistance. When this value is determined for single-core cables belonging to a certain cable line it becomes possible to determine the actual reduction factor, inductive influence, and sequence impedance of the considered cable line by using a standard and well-known calculation procedure.</p>

Technologies Related to Intelligent Grounding Box of High-Voltage Transmission Cable

The high-voltage cable line plays an important role in the transmission of electricity in the city network. The effective grounding of the high-voltage cable is of great significance to ensure the normal operation of the cable system. There is an increasing demand for the intelligence of grounding boxes of high-voltage transmission cables. In this paper, aiming at the heating problem of the grounding box, the overall design scheme and key technology of the cable intelligent high-voltage grounding box are proposed. The intelligent high-voltage grounding box has various electrical functions of the traditional grounding box. It also has cable circulation monitoring, waterproof, fireproof, anti-theft, and alarm functions. Remote control and management of intelligent grounding boxes can be realized through GPRS.

Reduction of Overvoltages under Connection on a High-Voltage Cable Line Due to Optimal Controlled Switching

The purpose of the work is to develop a mathematical model of a cable transmission line, which allows modeling and choosing the optimal conditions for controlled switching to limit overvoltage at the development and design stage. The goal is achieved by solving the problem of determining the initial angle of each phase, so that each phase has an initial switching angle equal to zero with a time delay. A high-voltage cable line for a voltage of 330 kV, implemented using Matlab, has been chosen as the object of study. The most significant result is the method of numerical simulation of the cable line that allows you to analyze transients when each phase of a three-phase cable line is connected to a three-phase source with a time delay, the switching angle of all phases is zero. This, in turn, makes it possible to limit switching overvoltages. The significance of the results obtained lies in the possibility of the proposed technique to choose the optimal conditions for controlled switching, which makes it possible to use it in the design of switching nodes, as well as the use of controlled switching to eliminate unwanted electrical transients during planned switching. The simulation results showed that the greatest effect of using numerical simulation is when each phase of a three-phase cable line is connected to a three-phase source with a time delay of 1/150 second, then the switching angle of all phases is zero, which makes it possible to limit switching overvoltages. Keywords: three-phase cable line, switching overvoltage, transient processes, controlled switching, theory of multipoles, modeling of electrical engineering objects.

Reduction of High-Voltage Cable Line Capacity Caused by Implementation of Magnetic Field Shielding Techniques

The paper deals with a capacity of high-voltage cable line made of three single-core cross-linked polyethylene insulated power cables. We consider three cases. First is a single-point bonded cable system when no magnetic field shielding technique is implemented and the capacity achieves maximum values. Second is a solidly bonded cable system when a thermal effect of induced shield currents causes a capacity reduction. The third case under study is a single-point bonded cable system covered by the passive loop. The passive loop mitigates the cable line magnetic field as well as the solidly bonding does, but also the thermal effect of passive loop currents reduces the capacity. The goal of the paper is to evaluate the relative change of cable line capacity when implementing magnetic field shielding techniques comparably to unshielded case. To achieve the goal we use a standard IEC 60287 when calculating the cable line capacity in the first and the second cases, and a thermal field simulation in the third case. The capacity is evaluated by successive approximations. Iterations are stopped when the conductor reaches the maximum operating temperature. We show that the increase in cable spacing does not guarantee the capacity increase when the solid bonding of cable shields or the passive loop is used. The most significant result is the substantiation of the advantages of passive loop, which provides the greater capacity in comparison with solid bonding at equivalent magnetic field shielding efficiencies. The obtained results can be used when choosing the type of bonding and the technique of cable line magnetic field mitigation.

Application of the Wave Channels Method to Analyze the Switching Overvoltages in Energizing a High-voltage Cable Line

A study of cable line failures shows that a large number of faults occur in the connecting and terminal couplings of 110--500 kV power lines. Overvoltages caused by operational switching in the substation switchgear circuits contribute to the total number of failures. The switching overvoltage amplitude and frequency depend on the parameters of the source, switched circuits, and switching moment. The aim of the study is to identify the network and switched circuit parameters affecting the maximum overvoltage excited by energizing a 400 kV cable line and to determine the degree of their influence. The following factors are considered: switching phase, cable line length, source inductance, and line residual charge. The analysis was carried out by the wave channels method. To achieve this goal, an analysis model was developed in the EMTP-RV software environment, which made it possible to calculate the electromagnetic transients excited by cable line switching. The model has been verified with respect to the surge propagation velocity along a coaxial wave channel. Overvoltage calculations have shown that the switching phase and the line charge availability in the pre-switching operation mode have the most significant effect on the overvoltage value. The obtained study results apply to high-voltage electrical networks containing cable lines. The study results made it possible to quantify the degree to which the considered factors influence the overvoltages excited by switching 400 kV cable lines and to assess possible exceeding of the values permitted by the relevant standards, which will make it possible to have a preventive influence on the number of failures.

ПОТЕНЦІЙНІ ЗАСОБИ ЕКРАНУВАННЯ МАГНІТНОГО ПОЛЯ ПІДЗЕМНИХ СИЛОВИХ КАБЕЛІВ У ПОЛІЕТИЛЕНОВИХ ТРУБАХ З КОМПОЗИЦІЙНОГО МАГНІТНОГО МАТЕРІАЛУ

The magnetic field of the medium- and high-voltage underground power cable line, laid in composite polyethylene pipes having magnetic properties, with the use of special loose-fill/fill-up soil of different dimensions (bulk) is studied by computer modeling. The pipes and additional soils around and near the cables are made of a composite material with effective magnetic properties and can act as a magnetic shield that reduces the level of the field on the ground. The effi-ciency of field shielding depending on the height and width of the composite loose-fill/fill-up soil is analyzed. The exis-tence of the optimal not large (in height) fill-up soil for the best mitigation of the magnetic field on the ground directly above the cables and the influence of the width of the loose-fill/fill-up soils on the shielding efficiency are revealed. The characteristic features of the magnetic field distribution and the field level depending on the availability or non-availability of composite loose-fill soil are presented. The advantages of (trefoil) cable arrangement in one pipe with additional composite loose-fill and fill-up soil are shown. References 30, figures 5.

Principle and Verification of an Improved Algorithm for Cable Fault Location Based on Complex Reflection Coefficient Spectrum

Diagnostic methods for fault location in cable insulation have become increasingly vital with the development of long-distance cables. This article presents an improved method for fault location based on the complex reflection coefficient spectrum (CRCS). First, a mathematical model for a long high-voltage cable line with consideration of a distribution-parameter circuit of cable joints is established in the frequency domain, and the CRCS of the cable with joints is analyzed. Next, based on the principle of frequency domain reflectometry (FDR), an algorithm in time-frequency conversion which uses the CRCS as the analysis spectrum is proposed. And the positioning sensitivity of the method is improved by implementing a data process adopting a Chebyshev window function which is controllable and reduces the sidelobe effect effectively. Furthermore, the improved method is evaluated by performing the simulations and two field verification tests. In a field test for a 5.1-km-long 110 kV cable, the multiple cable joints could be located effectively, and the relative error is between 0.14% and 1.49%. Then, the method was conducted for the positioning of a high-resistance fault and multiple joints on a 2.7-km-long 110 kV cable and the relative error is 0.37%. It is worth noting that the cross-bonding links of both cable tests were artificially replaced with temporary links straight across each joint. For the cross-bonded cable system, the test result shows that an obvious reflection is found at the cross-bonding point, which can reduce the reliability and accuracy of the present method.

The device for monitoring the insulation breakdown zone of power cable lines in distribution networks with isolated neutral system during high-voltage diagnostic

The article considers an electrical device designed for diagnostic work in distribution networks of 6-10 kV, namely, the determination of damage zones in case of failure of insulating materials of cable lines during high-voltage diagnostics with a rectified voltage of negative polarity. The novelty of the developed device is its ability to connect directly to a high-voltage cable line without additional matching devices. The device is capable of detecting damage zones in lines up to 10 km remotely with an error of up to 0.2% of the cable length. The prefix allows you to fix any variants of damage to single-phase and three-phase cable lines with high transient resistance at the site of damage without the operation of “burning” insulation, which significantly reduces the time of repair work at the controlled facility.

Огляд систем контурного екранування для нормалізації магнітного поля кабельних ліній високої напруги

The paper is devoted to the review of known passive loop systems that can be used to normalize the high-voltage cable line magnetic field. The purpose is to identify the most promising systems. We review the most cited scientific papers and patents about the reduction of the power line magnetic field. We identify the top research groups engaged in the design of passive loop systems. The two groups are from Italy, the one each is from Spain and Ukraine. The passive loop systems developed by each group have their own features. We classify the systems according to the following characteristics: the number of passive loops in the shielding system, the shape of passive loops used in the shielding system, and the way to increase the shielding efficiency of cable line magnetic field. According to the number of passive loops, the systems can be divided into three types: single-element, double-element and multi-element. According to the shape of passive loops, two types of shielding systems can be distinguished, namely, the systems using rectangular passive loops and the systems using passive loops made of three cables connected in parallel. According to the method of the shielding efficiency increasing, the system can be divided into four types: the first use ferromagnetic cores covering power and shield cables, the second use additional capacitors connected to shield cables, the third use a unique arrangement of loops between the cable line and the shielding area, the fourth use an increase in the cross-section of shield cables, respectively, an increase in the quantity of metal. The review shows the most promising passive loop systems for normalizing the high-voltage cable line magnetic field are single-element systems with additional cores, namely «High Magnetic Coupling Passive Loop» and «Single-loop shield with ferromagnetic cores and asymmetric magnetic coupling». Keywords: magnetic field, shielding, cable line, reference level, power frequency

Modern Approaches to Fault Location in High-Voltage Cable Lines

Prompt fault location in power cables with high accuracy is a measure aimed at achieving more reliable operation of the power grid system, in which the loss of electrical insulation strength is among the main factors causing accidents in the system. The article discusses the causes leading to faults in high-voltage cable lines and substantiates the relevance of determining the most effective fault location methods. Modern relative and absolute methods for cable line fault location are reviewed, and a comparative characteristic of the scope and limitations relating to the implementation of these methods is given. The article shows the expediency of using the acoustic method for fault location in cable lines as the most universal one, and also the burning method if the cable laying scheme is not available. The article also presents a comparative analysis of modern mobile electrical laboratories as the most advanced means for automating fault location in high-voltage cable lines, which makes it possible to reduce the fault detection time and ensure accurate cable line fault location. The necessity of improving the designs of mobile electrical laboratories and reducing their overall dimensions to improve the convenience of operation under urban conditions is substantiated.

Model development according to increase in the active resistance of the conductor to ac current at the surface effect

Purpose. When alternating current with higher harmonics passes through the cable, heating is carried out by the root mean square value of all harmonics. Taking into account the different resistance of the cable depending on the frequency due to the effect of the surface effect, it is advisable to calculate the coefficient of increase in the total current resistance, assuming the action of each harmonic as independent. However, there are prerequisites to consider existing calculation models difficult for algorithmic implementation in software packages. Therefore, the purpose of the work is to develop a calculation model to take into account the increase in the active resistance of the conductor to alternating current due to the surface effect for further use in simulation modeling packages such as, for example, MATLAB.
 Methodology. Methods of linear algebra, linear regression, defining the coefficient of determination.
 Findings. Dependencies for determining the resistance value of high-voltage cable lines to high-frequency currents, which take into account the cross-section and harmonic composition of the current, have been obtained. According to the existing and substantiated graphs (dependencies) obtained on the basis of classical expressions from the literature, new simplified calculation dependencies were obtained (for the cross-section of copper cable lines 240 - 1000 mm2) when current harmonics above the fifth at a base frequency of 50 Hz. Such calculated ratios will allow taking into account several harmonic components of the current during line heating in the MATLAB Simulink software environment.
 The obtained values of the coefficient of determination in defining the calculated dependencies are close to 1, which indicates the correctly selected type of equation and the correctly selected coefficient k for different cross-sections of the cable line.
 Originality. The scientific novelty lies in the development of a new dependence, justified by the high value of the multiple correlation coefficient, the correction factor for the increase in the resistance of the cable core from the harmonic number and the empirical coefficient of the regression model, taking into account the cross section of the cable line.
 Practical value. The practical value of the work consists in obtaining dependencies that can be used in analytical and simulation models when determining the amount of heating of cable lines taking into account the current of harmonics above the fifth at a base frequency of 50 Hz. Such an application will allow in many cases to replace the physical experiment with a simulation in the MATLAB Simulink software environment, which will reduce the necessary human and material costs.

Selective PD Measurements on DC Cable Joints Using a HFCT-Balanced Circuit Arrangement

Due to the many advantages of medium-voltage (MV) and high-voltage (HV) DC cable transmission lines and the possibility of converting AC transmission to DC transmission, this technology is becoming increasingly relevant. One of the most important diagnosis tools used to investigate the condition of the insulation of highvoltage cables is to apply partial discharge (PD) measurements. Cable joints and terminations are of particular importance, as these represent weak spots due to human interaction. Especially under DC voltage, it is of crucial importance to determine whether the detected PD pulses occur inside or outside the cable accessories.For this purpose, a PD test method for cable joints using two high-frequency current transformers (HFCT) was optimized with modern electronic devices, including an instrumentation amplifier and a modern PD measuring instrument. Two HFCT with opposite winding directions were placed on the outer semi-conductive layer on both sides of a cable joint. The signals were fed into an instrumentation amplifier to separate the PD pulses originating from inside and outside the cable joint. This method automatically suppresses PD pulses occurring outside the cable joint and was tested on a 12/20 kV AC cable joint under DC voltage and with thermal and electrical stress.

METHODS FOR MITIGATION OF MAGNETIC FIELD GENERATED BY UNDERGROUND POWER CABLES IN POLYETHYLENE PIPES MADE OF COMPOSITE MAGNETIC MATERIAL

The magnetic field of a high-voltage (330 kV) underground single-circuit power cable line, laid in a polyethylene pipe having magnetic properties, with the use of special loose-fill/fill-up soil of different dimensions (bulk) is studied by computer modeling. The pipe and additional soil around and near the cables are made of a composite material with effective magnetic properties and can act as a magnetic shield that reduces the level of the field on the ground. The efficiency of field shielding depending on the height and width of the composite loose-fill/fill-up soil is analyzed. The existence of the optimal not large (in height) fill-up soil for the best mitigation of the magnetic field on the ground directly above the cables, and the influence of the width of the loose-fill/fill-up soils on the shielding efficiency are revealed. The characteristic features of the magnetic field distribution within the considered shielding elements of the cable line depending on the availability or non-availability of composite loose-fill soil and the height of the fill-up soil with effective magnetic properties are presented. The shielding efficiency of underground single-circuit three-phase power cable lines when using the magnetic fill-up soil with a certain small height (volume) is grounded. References 11, figures 4.

Dimensioning of Reactive Power Compensation in an Autonomous Island System

In this paper, a method for sizing the reactive power compensation in a non-interconnected island power system is presented and applied to determine the necessary inductive reactive power compensation for the autonomous power system of Rhodes Island, Greece. The Rhodes power system is often confronted with an excess of reactive power, as a result—inter alia—of underground high-voltage (HV) cable lines and distributed generation penetration. Reactive power compensation is typically a local issue in power systems, usually aiming at maintaining an acceptable voltage profile on specific transmission segments, e.g., long underground or submarine cables. In autonomous systems, however, where network lengths are relatively short, reactive power compensation is meant to address the overall reactive power equilibrium of the system. The proposed method follows a three-step approach. First, power flow analysis is conducted to determine the size of the maximum compensation that may be necessary, i.e., the compensation size that practically allows unit commitment to be conducted without being constrained by reactive power considerations. Then, a unit commitment and economic dispatch model is executed over the course of a year to determine the optimal compensation size, using the output of the power flow analysis to formulate reactive power balance constraints. Finally, the results of the economic optimization are assessed in terms of dynamic security to verify the feasibility of the optimal solution.

Designing of High Voltage Cable Bonding with Intelligence Algorithms to Avoid Cable Insulation Faults and Electroshock in High Voltage Lines

The insulation fault is a major problem in high voltage cable lines. The major factors in the insulation faults are harmonic currents and the metal sheath voltage (MV) that occur on the metal sheath of cable. MV and harmonic distortion should be minimized to prevent insulation faults. Thus, sectional solid bonding with different grounding resistance (SSBr) method is developed as a new bonding method for minimizations of harmonic current and MV. Also, SSBr should be optimized by optimized according to minimum MV and harmonic distortion rate of high voltage cable. Inertia weighted particle swarm optimization (iPSO), particle swarm optimization (PSO), genetic algorithm (GA) and differential evolution algorithm (DEA) are used for optimization of SSBr, and three groups the prediction methods are used separately as objective function of the optimization methods to determine minimum MV and harmonic distortion. These groups are neural networks, hybrid neural networks and regression methods. Hybrid neural network with inertia weighted particle swarm optimization (H-iPSO), linear regression and feedforward backpropagation neural network are selected from their groups according to training errors. Solid bonding method is widely used for bonding of high voltage cable, and solid bonding is simulated in this study. When solid bonding is used for bonding of cable, maximum harmonic distortion rate is measured as 8.15 %, and maximum MV is measured as 1086 V. When H-iPSO is used as prediction method, and PSO is used as optimization method, maximum harmonic distortion rate is measured as 5,28 %, and maximum MV is measured as 57 V. Namely, both insulation fault and electroshock can be prevented by the optimized SSBr method.

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ НАГРЕВА ТОКОПРОВОДЯЩЕЙ ЖИЛЫ СИЛОВОГО КАБЕЛЯ ДЛЯ УЧЕТА ЭЛЕКТРОТЕПЛОВЫХ ПРОЦЕССОВ В ЦИФРОВЫХ ДВОЙНИКАХ КАБЕЛЬНЫХ ЛИНИЙ

This article deals with the implementation of diagnostics and monitoring of the current-conducting part and insulation state of high-voltage cable lines in real time using digital twins. The problems of thermal accounting and the fea-tures of modeling electrothermal heating processes in power cables are determined. A mathematical electrothermal model of a power cable for a cable line digital twin is proposed, based on the decomposition of its dynamic thermal resistance in-to the sum of exponential components, which makes it possible to calculate the instantaneous values of the heating temper-ature of a current-conducting cable core in real time with insignificant amounts of calculations on the discretization interval of the calculation. The results of calculation using the heating temperature model for a single-core power cable with a three-phase short circuit in the network are presented.

ІНТЕЛЕКТУАЛЬНІ ТЕХНОЛОГІЇ МОНІТОРИНГУ ТЕХНІЧНОГО СТАНУ СУЧАСНИХ ВИСОКОВОЛЬТНИХ КАБЕЛЬНИХ ЛІНІЙ ЕЛЕКТРОПЕРЕДАЧІ

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.

ОСОБЛИВОСТІ ЕКРАНУВАННЯ МАГНІТНОГО ПОЛЯ ПІДЗЕМНОЇ ТРИФАЗНОЇ КАБЕЛЬНОЇ ЛІНІЇ ЗА ДОПОМОГОЮ НАСИПНОГО КОМПОЗИЦІЙНОГО ҐРУНТУ З МАГНІТНИМИ ВЛАСТИВОСТЯМИ

The computations of the magnetic field generated by high-voltage (330 kV) underground power cable line with special fill-up soil having different dimensions (bulk) are carried out by the two- and three-dimensional computer models. The supplementary soil above the cables is the composite material with effective magnetic properties and serves as a magnetic shield. The computer results obtained by 2D and 3D models are compared. The efficiency of magnetic field shielding depending on the magnetic permeability, width, and height of the fill-up soil is studied. As revealed, there is the optimal small soil height for the best magnetic field mitigation on the top of the ground directly over the cable line. In addition, the width of the magnetic soil has an appreciable effect on shielding efficiency. The shielding of underground single-circuit three-phase power cable lines is efficient only when using the magnetic fill-up soil (or ordinary external screen made of magnetic materials) with enough small height. References 14, figures 7.

Life cycle cost assessment method considering multiple factors for economic evaluation of cable line steel brackets

In China, the bracket of underground high voltage cable transmission line is mainly made of various carbon steels. However, no unified standard exists for type selection of cable brackets in practice. Here, a selection method of the bracket based on life cycle cost assessment is proposed from the viewpoint of technical economy, in which the size of brackets, steel grade, carbon steel corrosion and eddy current loss are considered as influencing factors to the costs. Stress performance analysis under identical pole arm stress constraints is employed to determine the size and grade of carbon steel which influences the initial cost. And 3D coupled electromagnetic fluid-dynamical and thermal finite-element analysis is applied to calculate the eddy current loss of cable brackets which influences the operation cost. Meanwhile, multi-physics coupling analysis and experiment are conducted to prove the correctness of loss simulation calculation. Tafel curve measured by electrochemical corrosion experiment is used to obtain the corrosion rate of carbon steel which influences the maintenance cost by affecting service life of brackets. A case study is demonstrated, and the results show that the channel steel type is the most economical for the commendatory and the proposed method is effective.