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The early fault of a cable is usually a incipient fault, which is difficult to find and can easily develop into an insulation breakdown fault. Thus, it is of great significance to quickly and accurately find an incipient cable fault. This paper presents an fault location method for cable insulation based on the electric quantities of both ends. Based on the equivalent circuit model of three-phase single-core cable distribution parameters, the calculation method of the voltage along the cable is derived. The equivalent model of cable insulation in resistive and capacitive parallel is proposed and applied to the early fault modeling of cable. On the basis of the calculation formula of the voltage along the cable and the electric quantity at both ends of the cable, the analytical expression of the cable fault location is obtained by solving the fault equation directly. Extensive simulations show that the algorithm, this method can locate the incipient fault accurately, and is not affected by the fault point, fault resistance and fault inception angle.

Cable termination fault is one of the most important problems for high voltage underground cable lines (HVUCL). Harmonic current (HC) and the sheath current (SC) are causes of cable termination faults of HVUCL. The sheath voltage (SV) of cable increases due to SC and HC also. So, the electroshock risk for human occurs. In this study, cable termination faults are examined for long HVUCL that is connected to electric network with high harmonic distortion rate. In literature, solid bonding (SB) and sectional solid bonding (SSB) methods are used to reduce harmonic distortion rate and SC effect in HVUCL. However, when SB and SSB methods are used for bonding of long HVUCL, harmonic distortion limit and touch voltage limit are exceeded. Therefore, the modified SSB (MSSB) method is developed for bonding of long HVUCL. SV of HVUCL should be known to use MSSB for bonding of long HVUCL. Then SV of HVUCL is forecasted by using artificial neural network and hybrid artificial neural networks (HANN) before the long HVUCL is installed. MSSB parameters should be optimized, so that optimization methods are used for optimization of MSSB and HANN. When MSSB method is used for bonding of long HVUCL, harmonic distortion limit and touch voltage limit are not exceeded under high harmonic distortion conditions.

Based on the Zhoushan alternating current (AC) 500kV cross-linked polyethylene (XLPE) submarine cable project, a method of metal sheath grounding via a low resistor, a low reactor, or a low resistor in parallel with a reactor at both terminals of the cable to reduce the power loss has been proposed in this paper. By numerically modeling the submarine cable system with the PSCAD/EMTDC software, the voltage and current distributions, and power loss on the sheath, armor and total submarine cable under three types of grounding impedors are calculated. The results show that with the increase of resistance value or inductance value, the sheath current decreases, and the armor current and sheath voltage increase, but the overall loss of the submarine cable decreases. When the submarine cable is operating under normal, short-circuit or transient conditions, in which the sheath voltage does not exceed the critical condition of these allowable values, the way that the sheath is grounded via a low resistor is the most beneficial to the power loss reduction. When the corresponding critical resistance value is 2.1 ohms at the start of cable and 1.3 ohms at the end respectively, it will reduce the power loss of cable for one phase 23.5% and the total power loss including resistors for one phase 14.2%, which is conducive to improving both the safety and operation economy of submarine cable.

Due to recent advances, the numerical analysis of submarine three-core armored cables can nowadays be developed through the finite element method (FEM) in a small slice of the cable. This strongly reduces the computational burden and simulation time. However, the performance of this ultra-shortened 3D-FEM model is still to be fully assessed with experimental measurements. This paper focuses on this validation for an extensive variety of situations through the experimental measurements available in the specialized literature for up to 10 actual cables. In particular, it deals not only with relevant calculations at power frequency, like the series resistance and inductive reactance or the induced sheath current, but also with other aspects never analyzed before through 3D-FEM simulations, such as the zero sequence impedance, the magnetic field distribution around the power cable, as well as side effects due to the nonlinear properties of the armor wires. All this considering different armoring and sheath bonding configurations. Results show a very good agreement between measured and computed values, presenting the ultra-shortened 3D-FEM model as a suitable tool for the analysis and design of three-core armored cables, and opening the possibility to reduce the need of extensive experimental tests in the design stage of new cables.

Long-distance cables are often damaged by external forces due to site construction, resulting in protective layer grounding fault. Conventional fault location and detection methods, such as bridge method and traveling wave method, require on-site measurements along the cable, which results in heavy maintenance workload. For this reason, a method of online diagnosis and location of high-voltage cable based on sheath current is proposed. The simulation results show that when a fault occurs, the sheath current will change with the change of fault location and grounding resistance. Therefore, the external insulation faults of cables can be monitored, diagnosed and located on-line based on sheath current.

WOS: 000443167700004, The sheath current causes cable faults and electroshock risk in high voltage underground cable lines. Also the sheath current increases cable temperature and it reduces cable ampacity. Hence, cable performance decreases due to the sheath current. Different precautions can be taken to reduce the sheath current effects in high voltage underground cable line. However, primarily the sheath current must be detected at the project phase of high voltage underground cable line. In literature, artificial neural networks are used for forecasting studies. In this study, artificial neural network (ANN) is used with particle swarm optimization, particle swarm optimization with inertia weight and genetic algorithm to generate hybrid ANN methods for forecasting of the sheath current. High voltage underground cable line is modeled in PSCAD/EMTDC to measure the sheath current of different high voltage underground lines, and the obtained data from PSCAD/EMTDC are used to train artificial neural network based hybrid methods to forecast the sheath current of any high voltage underground cable line. When particle swarm optimization with inertia weight is used with artificial neural network, hybrid ANN-iPSO method is developed. The results of ANN-iPSO are better than the results of ANN-GA and ANN-PSO. If ANN-iPSO is used to determine the sheath current, the sheath current of high voltage underground cable line can be determined at the project phase of high voltage underground cable line. Hence, the most suitable precautions can be implemented, and cable faults and electroshock risk can be prevented, also cable performance is increased in high voltage underground cable line.

In this paper,an online cable fault location method based on Short-Time Matrix Pencil Method is proposed. In the 110kV cross-bonded cable hybrid line with GIS, the method does not need to disassemble the GIS of the cable terminal, and extracts the transient current traveling wave from the sheath ground wire of the cable ends. The Short-Time Matrix Pencil Method is used to extract the signal abrupt point in the current traveling wave caused by the short-circuit fault occurs in the line, and achieves the purpose of fault location. The cable system model is established in PSCAD to simulate different fault types and distances. Compared with the commonly used wavelet analysis method, the results show that the method has higher feasibility and accuracy.

The field analysis for a configuration of sheath helix in the presence of a coaxial metallic rod and strongly magnetized plasma under two conditions, i.e. , is presented. The electromagnetic field components in the configuration are obtained. The effects of a coaxial metallic rod in a plasma-loaded sheath helix traveling wave tube by means of a theoretical approach, in which infinite magnetic field has been adopted to represent the plasma response, is investigated. We presume that for the finite beam term, the mode structures remain unmodified and only the eigenfrequencies are modified. Therefore, the growth rate of slow electromagnetic waves and so their dispersion relation is calculated. Effects of frequency and plasma frequency on the growth rate are investigated. The obtained results are graphically presented.

Due to the current spreading of wind farms all over the world and their vulnerability to lightning strikes, it is important to investigate the lightning electromagnetic transients in wind farms. Underground cables are one of the essential parts in wind farms that link the turbines with the electrical grid. This paper investigates how the ground conductivity and relative permittivity, struck wind tower position, and rise time of lightning current influence the lightning electromagnetic fields impinging the underground cable sheath. The three-dimensional finite-difference time-domain method is implemented for this study. The lightning current through the cable sheath and its associated electric field can be effectively mitigated by connecting the grounding systems of the wind towers by underground bare wires called as counterpoise. Accordingly, the mitigation effect of counterpoise on the lightning current through the sheath and its associated electric field is also investigated. The results show that the lightning current through the cable sheath and its associated electric field is higher with lower ground conductivity. Moreover, it is revealed that the effect of both ground permittivity and struck wind tower position on the associated electric field and the sheath current is dependent on the ground conductivity.

Traditional analysis of cable early state recognition is mainly based on one or several threshold values of electrical characteristics, but the calculation of threshold is often affected by measurement accuracy and external disturbance, which inevitably reduces recognition accuracy. The development of artificial intelligence provides a new way to solve this problem. This paper presents a deep convolutional neural network (CNN) recognition method for early state of 10 kV single core cable based on sheath current. Firstly, waveform and energy characteristics which are extracted from the mutation information of sheath current by wavelet transform, are used to construct cable state recognition matrix. The mutational signal is detected by the cumulative sum (CU-SUM) method and intercepted by a set time window. Secondly, a 7-layer deep CNN is constructed according to the features of recognition matrix. Then the CNN model is trained by the adaptive moment estimation (Adam) method to get the recognition model of cable state. Finally, the proposed method is used to recognize cable early state by large number of samples which are obtained from the simulation of four cable states with PSCAD software. Compared with other methods, the results of simulation demonstrate that the proposed method has a high recognition accuracy.

Three-phase underground power cables can induce voltages and currents in their recover sheaths. The induced voltages and currents in sheath are undesirable. They generate heat losses and reduce the cable ampacity. Moreover, the induced voltages can generate electric shock to the workers, who maintain the power cables. It is very important to predict the sheath voltages and currents, which depend on different parameters, such as the sheath grounding system, the geometry of the cables, the gap between them, etc. In this paper, the voltages and currents induced in sheath for different installation of underground power cables (trefoil and flat formation) are studied and presented. For each case study of installation, the results of sheath voltages and currents have been computed and compared. Finally, the case of cross bonding with increasing of cable spans can reduce the sheath voltage significantly.

통신 회선에 대한 전력선 전자유도 전압을 측정할 때, 일반 통신 케이블의 쉬스 층 및 측정 대상 통신 회선 접지의 상호 접속 관계에 따른 전압 변화를 비교 분석하였다. 케이블 양측 쉬스 접지 저항이 평균 $42.6{\Omega}$ 으로 유사한 상태에서 쉬스를 분리 접지하고 유도 전압을 측정하면 쉬스 접지를 하지 않은 상태에서 측정한 유도 전압에 대하여 10 % 미만 감소된다. 어느 한 쪽을 공통으로 접지하면 약 50 % 감소되고 양측을 모두 공통으로 하면 90 % 넘게 감소된다. 이것은 국제전기통신연합(ITU)에서 제공하는 계산식으로 계산하였을 때의 결과와 유사한 것으로 분석되었다. 아울러 ITU의 계산식을 활용하여 양측 쉬스 접지 저항 값을 변화시킬 때의 유도 전압 변화를 시뮬레이션하여 비교 분석한 결과, 실제 현장에서 쉬스 접지 저항 기준이 $100{\Omega}$ 이고 전화 국사의 저항이 보통 $10{\Omega}$ 이하인 점을 감안할 때 측정 오차율은 약 10 % 이하가 된다. 【The change in induced voltage according to the relationship of ground connection between the aluminum sheath layer and a conductor pair in a general telecommunication cable is analyzed. When a measurement is practiced under the condition of separated sheath grounds with an averaged ground resistance of $42.6{\Omega}$ , the induced voltage decreases 10 % to the induced voltage without sheath grounds. The induced voltage decreases approximately 50 % in the case of a one-sided common ground and decreases by more than 90 % in the case of a both-sided common ground. This experimental result is similar to the values calculated using the methods of the ITU Directives. In addition, according to a comparison analysis utilizing this ITU method, the measurement error range will be below 10 % in the state of ground resistance of central office less than $10{\Omega}$ and for the terminal side with $100{\Omega}$ less or more.】

This paper presents a method for detecting different types of defects in the cable sheaths interconnected in a cross bonding configuration of a HV cable system installed in flat or trefoil layout using the sheath currents as input data. Three different defects have been analyzed: electric continuity loss of earth connection, short-circuit between sectionalized metal sheaths of a cable joint and link-box flooding. The sheath current has been calculated by two different approaches, one on the basis of theoretical equations, programed in MATLAB® and the other on the basis of ATP software simulating the cable system model. The results obtained using both methods have achieved a good agreement between them. A simple criterion by the means of a easy normalized code of four discrete levels 0, 1, 2 and 3 has been developed to distinguish the magnitude level of change of sheath currents in case of the indicated defect existence in order to trigger alarm.

In order to improve the practice in operation and maintenance of high voltage (HV) cable circuit and localize short circuit fault accurately and in a timely manner, this paper proposes a fault localization method based on the monitoring of sheath current in cross-bonded HV cable circuits. The fault current flow can be identified by analyzing the fundamental component of sheath current, which can be obtained by Fast Fourier Transform (FFT) of the monitored sheath current. The cable section where a fault occurs can be localized as both ends of the cable section current would flow in opposite direction. The sheath current signals in different fault location within different sections have been simulated with a selected high voltage cable circuit and under typical operational mode. A set of fault localization criteria have been proposed. Results indicate that the proposed method is feasible and effective in localization of HV cable short circuit faults.

Length of most underground power cable in nation is not so long. Therefore it is operated without conductor transposition due to low unbalanced ratio. However, if cable length is long, line constant of each cable will be different. Different line constant can induce unbalanced voltage and current of sheath. Also it can induce several induced interference. This paper describes the operation effectiveness through steady and transient analysis on transposition and untransposition of cable conductor. Especially sheath current and induced voltage are analyzed and compared in case of transposition and untransposition. EMTP is used for modeling and analysis.

In this work we propose that the dipole antenna can be fed directly through the coaxial cable, without any balun, when used with a perfect electric conductor (PEC) reflector placed at quarter wavelength distance. This configuration leads to a high impedance between the coaxial cable outer metal shield at the dipole feed point and the ground plane which restricts the current to flow on the outer metal shield of the coaxial cable.

The current and voltage in High Voltage DC (HVDC) line is not pure DC but contain superimposed ripple components. The current ripple in core of HVDC cable magnetically induces a voltage in the sheath, whereas the voltage ripple causes the flow of charging current from core to sheath. The knowledge of sheath voltage is necessary to ensure compliance with the specification of utility companies. In this work, we have reported that the models available in commercial Electromagnetic Transient (EMT) simulation software erroneously introduce a DC bias in steady-state sheath voltage and sheath current. We have also demonstrated that by removing the DC bias accurate steady-state evaluation of sheath voltage and sheath current is possible. Additionally, we have analyzed the sheath voltage and currents in HVDC cable considering different cable lengths and sheath grounding schemes. It has been found that grounding the sheath at the terminal of HVDC cable can limit the sheath voltage to acceptable levels without causing substantial joule loss in the sheath.

Single conductor cables are widely used in several types of installations over the last years, including the interconnection of wind parks to the power grid. Owing to the complexity of cable installations each configuration must be treated individually, regarding the use of sheath cross-bonding, the influence of grounding resistances and the use of sheath voltage limiters. In this study, a systematic investigation of the performance of a long-medium-voltage cable configuration is presented. Sheath voltages and currents are calculated during steady-state and short-circuit conditions for varying sheath arrangements using the ATP/EMTP software. Results are validated by field measurements. The analysis is also extended to include the investigation of overvoltages in the installation, during slow and fast transients, according to the basic insulation level for the cable system.

The transient electromagnetic fields during switching operation in gas-insulated substations (GISs) have rise times on the order of nanoseconds. These fields leak into the external environment through the discontinuities of gas-insulated modules and affect the control cables and induce the transient voltage on cables, which results in malfunctioning of the equipment. The amplitudes of the electric and magnetic fields could be a few tens of kilovolts per meter and a few hundred amperes per meter according to layout of GIS, respectively. In this work, the induced voltage in the central conductor of a control cable and the induced current in its sheath, which is parallel to bus duct in a GIS with rated voltage of 230 kV, are calculated. Influence of the sheath material on the induced voltage and the type of its grounding on the induced current are analyzed. Furthermore, the impact of installing ferrite rings over the control cable sheath in mitigating the induced voltage and current is investigated. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

This paper presents the research and development of an integrated high voltage (HV) power cable condition monitoring and fault localization system. The system consists of the functionalities of online dielectric loss (DL) monitoring, outer sheath and earthing system condition monitoring, and a rapid fault localization system, all based on monitoring of cable sheath currents. Within the distributed sheath current monitoring system, the DL monitoring is achieved via subtraction of sheath currents at different points of a sheath loop, allowing the relative change in DL among the three cables to be trended. Through modelling and analysis of monitored sheath currents, cable outer sheath and cross-bonding connections can be monitored. This includes alarming of theft of earthing conductors which contributed to a large proportion of HV cable failures. The distributed sheath current monitoring system can also be used to record short circuit current between the instant of cable fault and the moment when the protection system actuate, for rapid fault localization. For each of the three applications, the fundamental research and initial results are provided.

The sheath current generates on metal sheath of underground cable, and it causes cable faults, electroshock risk and reducing of cable performance in high voltage underground cable line. Therefore, the sheath current must be reduced, and if the sheath current can be determined before high voltage underground line is installed, the required precautions can be taken to reduce the sheath current. Hence, cable faults and electroshock risk are prevented, and cable performance increases. In this study, simulations of high voltage underground cable line are made in PSCAD/EMTDC, and the sheath current is forecasted by using hybrid artificial neural network (ANN) method. Differential evolution algorithm (DEA) and particle swarm optimization (PSO) are used to generate hybrid ANN method. The results of hybrid ANN method are better than classic ANN, and the results of DEA-ANN method are better than PSO-ANN. Also DEA-ANN can be used in forecasting studies.

There will be circulating currents in metal sheaths of cross bonding cables when length or arrangements of three segments are different. The phasor sums of sheath-induced voltages in sheath cross bonding cables are first analyzed. Then, the circulating currents are calculated by EMTP with varied lengths of three segments to get the sample data, which are in turn used to fit out the empirical formula for evaluating sheath circulating currents. Finally, the principle of mixed arrangements is proposed to reduce sheath circulating currents in sheath cross bonding cables when the lengths of cable segments are not equal.

The importance of the sheath current wave such as Sommerfeld's single-wire wave (SSWW) increases in electromagnetic compatibility. In order to measure the reflection coefficient of SSWW equipment under test (EUT) (for example an absorbing clamp), we can use the slotted line method. But this method takes much time and more efforts, because the voltage or current distribution must be measured along the line at a lot of different positions. However, in order to produce a more rapid determination of the reflection coefficient of an SSWW EUT, we have designed an SSWW directional coupler to measure it. In this paper, an improved technique for measuring the -parameters of an SSWW backward coupler is investigated. We present the equivalent circuit model of this coupler and discuss results. The measured -parameters will be used to determine the reflection coefficient of an SSWW EUT. As an application of this technique, a pyramidal foam absorber and an absorbing clamp are used as EUT. The reflection coefficient of the latter is measured twice: first using the slotted line and then with the coupler. A comparison between both results is presented.

In this paper experiments and theoretical treatments [1] on 1.5 KJ coaxial plasma discharge device have been carried out to show, plasma current sheath, PCS, motion in coaxial plasma discharge by studying: the effect of nitrogen gas pressure in the range from 1 to 2.2 Torr and the axial position of PCS along the coaxial electrodes on the modification factor, actual drive parameter, PCS curvature and shape (thickness). Also the dynamics of PCS along the coaxial electrodes due to the combination effect of induced azimuthal and axial magnetic fields induction has been detected experimentally by using a magnetic probe technique.

The sheath in underground power cables serves as a layer to prevent moisture ingress into the insulation layer and provide a path for earth return current. Nowadays, owing to the maturity of manufacturing technologies, there are normally no problems for the quality of the sheath itself. However, after the cable is laid in the cable tunnel and is operating as part of the transmission network, due to network construction and some unexpected factors, some problems may be caused to the sheath. One of them is the high sheath circulating current. In a power cable system, the uniform configuration of the cables between sections is sometimes difficult to achieve because of the geometrical limitation. This will cause the increase of sheath circulating current, which results in the increase of sheath loss and the decrease of permissible current. This paper will study the various characteristics and effects of sheath circulating current, and then will prove why the sheath current rises on the underground power cable system. A newly designed device known as the Power Cable Current Analyser, as well as ATP simulation and calculation equation are used for this analysis.

This paper has investigated surge propagation and overvoltages on a coaxial cable when a lightning current flows into the metallic sheath based on experiments, EMTP simulations and analytical calculations. At the instance of the current flowing into the sheath, the core voltage becomes the same as the sheath voltage, which is given as a product of the sheath surge impedance and a half the current, following the theory of electrostatic shield. Thus no voltage difference appears between the core and the sheath across the insulator. When a traveling wave arrives at a transition point, i.e. cable termination, an insulating or crossbonding joint, the voltages change suddenly and a significant voltage appears across the insulator. An EMTP simulation shows that the overvoltage across the insulator exceeds 1200kV at a crossbonded node on a 400kV underground cable when an ac source voltage is in the opposite polarity of the lightning surge voltage on the sheath and the inductance of a crossbonding lead wire is taken into account. The high overvoltage appears in a narrow region of the cable between the current injected node and the crossbonded node due to traveling wave reflection between the nodes. The phenomenon investigated may occur if there exists a pinhole or a watertree on an underground cable.

In this paper, we calculated the induced sheath voltage in metallic sheath/shield of single-core cables operating in double circuit by considering influence of arrangement and phase distance; with the aim of providing optimal value of phase distance and proper arrangement to reduce the induced voltage. Five different arrangements of the cables are used to investigate the effect of a single point bonding and the double point bonding on induced voltage. Formulae for different arrangements are derived using IEEE guide to calculate induced sheath voltage. Out of five arrangements, independent horizontal and vertical arrangements have provided better results. It is found that the independent horizontal arrangement provides lesser maximum induced voltage of 132 V/km but higher overall induced sheath voltage of 64.28 V/km when compared to the vertical arrangement. The vertical arrangement has the values of maximum induced sheath voltage of 138.8 V/km and the overall induced sheath voltage of 27.79 V/km. This causes obvious decrease in the circulating current in the metal shield of the cable which makes independent vertical arrangement better than independent horizontal arrangement with respect to personnel safety. These findings can be used to suggest proper phase distance, radius of the cables and their arrangements when operating in double circuit to reduce the induced sheath voltage in metal sheath of a cable.

To solve the problem of fault location in 20 kV medium-voltage distribution network cable line, a method based on sheath grounding current is presented in this paper. When unsymmetrical earth fault occurs, the sheath grounding current contains three ingredients. After analyzing the relationship between induced circulating current flowing in cable sheath and zero-sequence current flowing in the cable core, it is found that the sheath grounding current has characteristics obvious enough to distinguish internal or external fault type. Based on this, sheath grounding current overflowing criterion is proposed which is effective to locate the fault section of cable line. At last, validity of the sheath grounding current overflowing criterion is verified by RTDS simulation results.

Flow of current in a cable conductor generates a magnetic field which could induce current flow in the metallic cable shield or sheath. This paper examines induced voltage calculation in multi-circuit of the cables with the hope of proposing new methodology for induced sheath voltage computation in metallic shield of a single-core power cable operating in a triple circuit. This study considers a few examples to demonstrate the method of examining the induced voltage in single, double and triple-circuits. The calculated values for induced voltages were 0.079 V/m, 0.074 V/m and 0.068 V/m for triple, double and single circuit. It is found that induced sheath voltage increased with the increase in number of the cables.

The magnetic field in the sheath of monopole plasma antenna or the helix antennas has been found to have a negative impact on its general functionality. The vertical and horizontal signals at predetermined angles had been compromised by the sheath effect. It was observed that this phenomenon is almost unnoticed because magnetization has the highest magnitude when the device is switch on/off. In microscopic scale (monopole plasma antenna), the sheath effect is due to femto spin demagnetization of particulates. However, in macroscopic scale (helix antenna), the sheath effect is due to signal impairment.

This paper presents the development of a correction coefficient for the International Electrotechnical Commission (IEC) Standard 60287-1-1 formula for the sheath loss factor of the middle cable in a touching flat formation. The solid sheaths are bonded and earthed at both ends of an electrical section. The reason for this correction is to take into account a nonuniform distribution of the losses within each sheath arising from the proximity effect. The coefficient is developed by using the filament method as well as the stochastic optimization algorithm based on differential evolution. The IEC formulae for the sheath loss factors of the outer cables, forming a part of the touching formation, do not need to be modified in order to consider the proximity effect.

This paper aims at checking the possibility that cable sheath faults in unipolar three-phase HV and extra HV cables with sheath cross-bonding systems can be detected by monitoring sheath-to-ground currents at the solid bonding ends of major cross-bonding sections. This goal is achieved by calculating such currents for some reference case studies of faults of the outer thermoplastic jacket in unipolar three-phase land cables for power transmission in flat formation. The case studies differ as to cable voltage ratings, resistance and location of the fault, symmetry of minor sections, and number of major sections. The results show that the aforementioned possibility does exist, particularly for some fault types and for sufficiently high cable load.

We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the RF parallel electric field emitted by Ion Cyclotron (IC) wave launchers, using a simple model of Slow Wave (SW) evanescence coupled with Direct Current (DC) plasma biasing via sheath boundary conditions in a plasma-filled 2-dimensional (parallel, radial) rectangle. Within a “wide sheaths” asymptotic regime, valid for large-amplitude near RF fields, our model becomes partly linear: the sheath oscillating voltage at open field line boundaries is a linear combination of elementary contributions by every source point of the radiated RF field map. These individual contributions are all the more intense as the SW emission point is toroidally nearer to the sheath walls. A limit formula is given for a source infinitely close to the sheaths. The decay of sheath RF voltages with the sheath/source parallel distance is quantified as a function of two characteristic SW evanescence lengths. Decay lengths are smaller than antenna parallel extensions. The sheath RF voltages at an IC antenna side limiter are therefore mainly sensitive to SW emission near this limiter, as recent observations suggest. Toroidal proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel anti-symmetry of the radiated field map. They could also justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

We have designed an integrated high voltage cable metal sheath circulation online monitoring terminal. The open-type current sensor, the circuit of data acquisition and the circuit transceiver of radiofrequency wireless has been researched and developed, real-time online monitor the changes of high voltage cable metal sheath circulation, monitor the data is transmitted to the management system of the data analysis through wireless. It has been installed on the site and tested.

A sheath model in an oblique magnetic field is build, which has one-dimension coordinate space and three-dimension speed space. The effects of magnetic field on the structure of RF sheath and parameter characteristics are discussed. The numerical simulation result shows that magnetic field has great effects on the sheath structure, especially in the region near the edge of sheath. Also, the magnetic field affects ion energy in the direction vertically to the board and incidence departure angle.

Plasma shocks can be magnetically driven during high current discharges in low-pressure gases, induced by an external electric circuit. Radial currents between two coaxial electrodes can be accelerated to velocities of the order of 10 cm µs−1, thus being an effective method to transform potential energy in kinetic energy. A series of experiments were conducted using a low energy plasma focus device to measure the dynamics of plasma shocks in coaxial tubes. The radial position of the current sheath near the closed end of the electrodes was determined by means of a magnetic probe. The pinching time at the open end of the electrodes was measured using a Rogowski coil. Both, the movement and shaping of the plasma sheath were modelled by means of finite elements. The sheath was represented by coupled conical segments carrying current, mass, internal energy and momentum. The Lorentz force accelerates each element in its normal direction, which leads to the continuous reshaping of the sheath. The numerical results are compared against the experimental data showing good agreement.

Sheath circulating current is increased by the electrical unbalance in underground power cable systems. Such unbalance is caused by the mixed burying formation and length unbalance between cross bonding minor sections. If the sheath circulating current rises in power cable systems, the loss caused by the current will be increased and the permissible current of cable will be reduced. The high sheath current may also cause the danger on person and cause the fault by the breakdown of insulation. Therefore, in this paper, the authors analyse the sheath circulating current in transient state and propose the current reduction device using reactor. Reduction effect is proved by the measurement of current and simulation using EMTP. In order to protect the reduction device in case of transient state, the authors propose the protection methods for the reduction device.

Power cables are playing an increasingly important role in the power grid because of the shortage of city land. The sheath loss is one of the main shortcomings of power cable. However, research on the sheath loss is limited so far because the multi-conductor model of cable lines with sheathes is difficult to build. What' more the great varieties of the cables and sheaths arrangement add to the difficulty. The arrangements of cables and sheathes mainly include: sheath transposition, cross-bonding, solid-bonding, one-point bonding and earth continuity conductor adoption. In this paper, the sheath loss of cables with different arrangements is studied and compared (based on the coupled line model). Besides, research is also carried out to find the cable arrangement which minimizes the total sheath loss of two circuits installed in the same tunnel.

A self-magnetic pinch diode is currently under extensive study in the Sandia Laboratory advanced radiographic development facility.

The application of cross-links at the cable joints and the arrester-groundings at the cable terminals undoubtedly reduces the ground potential and the sheath current in a cable system, however, such configuration builds an open circuit in the grounding conductor and stops the partial discharges (PD) pulses to travel. Thus very few pulse energy goes into the grounding wire, which is an industrial accepted checkpoint for PD defects through conventional sensors such as high frequency current transformers. To solve the problem, this paper introduced an innovative broadband PD sensor by using a capacitive jumper to bridge the PD propagation path. In this way, the problem of impedance mismatch at PD frequency is avoided, while an `open circuit' is maintained at power frequency. The sensor is tested in the laboratory with an oscilloscope for its sensitivity and detection bandwidth, while the latter reaches about 200 kHz ~ 87MHz. Such sensor was tested in a real 110 kV cable and shown the convenience and effectiveness in PD detection.

In Chap. 7, it was shown that the two-terminal method using a coaxial wave velocity with arrival instances extracted in the time domain is a good strategy for a fault locator system for crossbonded cables. However, the cable models implemented in simulations programs today does not include all layers and materials used in real-life cables and several references are studying disagreements between simulation results and field data for instance [1].

Some power system components, cable and cable system parameters will influence the characteristics of the first fault wave seen at the FLTs and thereby influence the ability to extract the necessary information for accurate fault location. In this section, the most important parameters are examined.

After a study of the different fault location techniques, it is clear that the online travelling wave method is well suited for crossbonded cables.

This paper presents the calculation of sheath voltages of flat and trefoil cables by varying phase currents. These sheath voltages are calculated by considering phases A, B and C respectively. The sheath voltages are compared and it is found that phase B current is more appropriate for both flat and trefoil formations due to the consistent growth in sheath voltage. In addition, the same sheath voltages are calculated by varying the spacing and radius.

Considering large charging capacitors and grounding feature of 500kV long-distance single-core oil-filled submarine cables, a new calculating method on circulation currents of sheath is proposed based on electromagnetic field theory and circuit laws. With the distributed parameter model of the wire core, the influence of current distribution along core wire and capacitance current on sheath circulation current is analyzed. The cable sheath losses can also be calculated conveniently. The results from on-site test demonstrate the feasibility and effectiveness of the proposed method. Further by analyzing the influence of the structural parameters and operating conditions of submarine cables on cable loss, multi-point grounding of sheath and reactive power flow optimization would be suggested as two effective loss-reducing measures for such kind of projects.

Formation of the radio-frequency driven sheath and resulting parasitic antenna loading in the ion cyclotron slow wave antennas are studied experimentally in the linear divertor plasma simulator NAGDIS-II. A phased loop antenna array with a poloidal mode of m =0 is used in the present ICRF heating experiment. A large DC voltage drop of about several hundreds volts is induced on the loop antennas with and without Faraday screen during high power RF heating and causes the additional power dissipation ( P sh ) due to the heat flux to the antenna current strap of ions accelerated by the RF driven DC sheath potential. This parasitic antenna loading is measured by calorimetric method and compared with that obtained from the conventional measurement of the antenna voltage and current. When a Faraday screen is employed to reduce the antenna–plasma interaction, P sh becomes much smaller than the radiated RF power. The net antenna loading for ICRF slow wave excitation is evaluated, taking account of the RF sheath dissipation.

We carry out a self-consistent analysis of the excitation of current on an overhead cable by a vertical current source. The ground plane is assumed to be a perfect conductor, but otherwise the solution obtained is quite general. It is shown, for the cable model adopted, two dominant modes are excited; one is the expected transmission line mode between the cable and the ground plane and the other is the coaxial mode between the center conductor and sheath. When generalized, results for the traveling wave source can simulate lightning, but this task is left for the future.