Despite being an experimentally well-studied phenomena, a consistent lacuna has always persisted in the theoretical and mathematical understanding of space charge dynamics in low-density polyethylene (LDPE). The macroscopic models reported so far in the literature seem to be insufficient and fail to predict the formation of homo- and hetero-charges near the electrodes and transport of charge packets. On the other hand, while microscopic models such as bipolar charge transport (BCT) model were able to explain homo-charge accumulation and movement of charge packets to a limited success, they are often fraught with assumptions such as neglection of diffusion phenomena and are structurally complicated when compared to macroscopic models. In this work, the authors have derived analytical solutions for space charge dynamics based on Maxwell's equations and transient space charge limited current (TSLC)-based volumetric current models, which take into consideration the measured absorption (slow polarization) and steady-state volumetric currents. The proposed analytical (macroscopic) model can thus predict the homo- and hetero-charge accumulation in LDPE, which is validated through comparisons with the experimentally measured space charge, wherein a remarkable agreement was observed. Furthermore, the relation between the transient volumetric current and space charge dynamics is reaffirmed.

This article presents detailed experimental and simulation investigations on the tracking and electro-thermal runaway in overhead conductor sleeves (CSs). The 90 degrees and 180 degrees overlapping configurations are extensively studied. The interface tracking inception voltage of the sleeve is experimentally determined under ac voltages for different operating conditions. An experimental setup is proposed to measure the surface and interfacial conductivity. The authors present FEM-based simulations to model the sleeve using the measured conductivity, and these simulations are extended until runaway. The results emphasize the effect of overlapping angle on the runaway and tracking. Furthermore, the efficacy of sleeve design is critically evaluated by correlating the simulation results with experimental data and a comparative analysis with covered conductor (CC) is also presented. The results offer insights into optimum design of CSs and are believed to be useful for power utilities.

This paper presents the effect of bulging on the electric field distribution of an AC cable. Bulging is a type of deformation or defect, where the cable undergoes swelling or expansion in a certain area, resulting in a non-uniform geometry. This may occur due to various reasons such as mechanical stress, thermal stress, overloading, excessive bending, and sometimes environmental factors. The effect of the extent of bulging has been investigated in a finite element method (FEM) based model with electro-thermally coupled simulations. The results are expected to provide useful insights into the design and operational aspects of the cables.

In many areas, such as speech processing, communication, and measurement systems, where the actual signal is not directly available, Wiener deconvolution is a widely used signal restoration technique. The accuracy of the estimated signal in Wiener deconvolution is determined by the unknown filter parameter. To compute this unknown parameter, complex and time-consuming numerical as well as iterative computation approaches were proposed in the literature, which also often compute an unoptimized unknown filter parameter. To address the computational problem and estimate a more accurate unknown filter parameter, the authors reported an analytical solution in a prior work for a given signal to noise ratio. However, it was revealed that the actual optimum parameter value also varies with noise also. In this paper, the authors propose a new analytical solution for optimum parameter estimation that includes noise as well. The authors compared the modified analytical solution to existing numerical computation methods for different values of Signal to Noise Ratio and demonstrated that the proposed methods' optimum parameter estimation is always close to the actual optimum value, which resulted in more accurate signal deconvolution. Proposed mathematical solutions are also verified with experimental signals, acquired in a laboratory.

In this paper, an attempt has been made to explore the driving point impedance function (DPIF) of the transmission line. This can be done by constructing the DPIF of a transmission line from sweep frequency response analysis (SFRA) data and comparing its frequency response with the measured frequency response. The DPIF has an extra edge when compared to other transfer functions since only one terminal end is required to be operated. The measured data must be represented as a polynomial in the form of "s," to construct a rational function. This rational function has to satisfy some properties so that the proposed ladder network can be synthesized. The conditions that must be satisfied are the numerically simulated data corresponds to DPIFs; the rational function generated should be real and positive. Of these, the first one can be checked by performing simulation. Carefully planned experiments are performed for this purpose. To check physical reliability, every function must conform to a Hurwitz polynomial. A generalized analytical equation for the driving point impedance function which is a function of polytopic numbers is also used for comparisons of the obtained impedance graph and derived equation. The results indicate excellent matching of frequency responses of impedance functions constructed from simulated SFRA and analytical function, thus establishing the feasibility of the application of the technique for transmission lines.

The electric field distribution within capacitors and cables is predominantly influenced by the geometrical profile of the electrodes. It is important to consider the presence of protrusions on the electrode surface, as they can significantly impact the electric field intensity. These protrusions can intensify the electric field, potentially leading to premature breakdown of the dielectric material. Hence, the presence of protrusions on the surface of electrodes in high-voltage capacitors holds immense significance and should be carefully considered in the design and manufacturing processes. In this paper, a capacitor model with protrusions is simulated in FEM-based COMSOL Multiphysics software. Electric field distribution is obtained and the effect of protrusion geometry on peak electric field is analyzed.

This article primarily discusses the phenomenon of inhomogeneous aging observed in a 220 kV in-service high voltage alternating current (HVAC) cable. The XLPE layer is peeled out circumferentially using a special lathe. The samples are subjected to various material characterization tests including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and dielectric spectroscopy. The results show significant differences in morphology among XLPE layers, which is in turn reflected in permittivity measurements. The local changes in permittivity are expressed mathematically to vary along the radial position and fit with the experimental data. The fit equations are used to estimate the electric field distribution inside the insulation bulk using a finite element method (FEM) software. The simulation results are also verified analytically. When compared to conventional field distribution with bulk consideration of permittivity and permittivity at the radial position, a significant enhancement in the electric field in the middle part of cable insulation is observed. The field enhancement is visualized with different accelerated aging permittivity data from the literature.

This article presents the electrothermal runaway characteristics of an extruded high voltage direct current (HVDC) cable in the presence of eccentricity, i.e., a misalignment in the axes of cable conductor and insulation, which is practically unavoidable in extruded cables. In particular, eccentricity in dc case assumes importance due to nonlinear, temperature (or load current)-dependent field dynamics as compared to alternating current (ac) case. The effect of eccentricity on electrothermal breakdown has not received adequate attention till now. In this work, the authors simulate the runaway in an HVDC cable and investigate the impact of eccentricity under different scenarios, such as short-time and long-time instability, using a comprehensive finite element method (FEM) model. The results show a drastic shift in phenomenon from traditional global thermal breakdown to local thermal breakdown due to eccentricity in power cables. The results are validated with analytical computations.

The use of power cables has increased enormously due to several advantages such as safety, durability, reliability, and quality of power supply without any interruption. To maintain these features, there needs to be proper testing of cable before use. This research paper presents a comprehensive and cost-effective method for the testing of cable. In this paper authors investigated three different method for the testing of cable experimentally and further simulated using FEM based software and concluded the best among three.

This paper proposes a novel broadband impedance spectroscopy through a sweep frequency response analysis approach for estimating the position of damaged insulation, particularly the site of water treeing. Water treeing is an undiagnosed issue in cables that does not result in a partial discharge until a catastrophic failure happens. Therefore, an attempt was made to pinpoint this kind of cable damage using impedance spectroscopy in this research. In addition, an analytical method based on the frequency location of zeros and their cumulative total and product is suggested for estimating the location of water treeing of different sizes in the insulation. To validate the suggested equations, tests were conducted on the test cable to generate water treeing based on a model based on the literature.

The use of overhead covered conductors and conductor sleeves plays a crucial role to provide insulation and safety from the environmental hazards in the power systems. Covered conductors have a rigid insulation layer over a bare conductor, which restricts their flexibility especially in hilly areas or wherever the sharp turn is required. In contrast, conductor sleeves offer a more flexible structure, allowing their easy installation, replacement if required, and are cost-effective. However, investigation of the optimal design of conductor sleeves requires an accurate measurement of the AC conductivity. In this paper, an experimental setup and its methodology for the measurement of AC conductivity on the surface and in the interface of conductor sleeves is proposed. Additionally, dielectric spectroscopy has been performed to determine volumetric AC conductivity.

Cable sheath provides shielding against moisture ingress and provides mechanical support to the insulation. However, due to current flowing in the conductor and phase voltage an induced current flows through the sheath, which degrades the cable's lifespan and potentially causes cable failures. Along with this, additional transients like busbar faults will degrade the condition of the insulation. For the energy distribution between the feeders, busbars are utilized and any fault in the busbar can lead to disruption in the power delivery. So, to ensure safety, a close monitoring of sheath current during busbar fault is important and this proactive approach helps to prevent further serious problems. In this paper, simulations are carried out to find the sheath current in different joints during busbar faults for different types of bonding.

In this paper, a study of high-frequency traveling waves on a transmission line is presented. Traveling waves are voltage and current waves that travel from the source end to the load end of any power equipment, especially of a transmission line during transient conditions. Short and medium-length transmission lines are represented by equivalent T or π-model, and electrical parameters of the line are considered as lumped parameters, but this is only feasible for the steady state condition of the system. However, whenever a transient took place or in the case of a long transmission line, these parameters are treated as distributed. In a lossy transmission line, traveling waves propagate with a velocity less than the speed of light. During normal operating conditions, the load of the transmission line matched with the surge impedance of the transmission line to avoid any reflection. However, whenever there is a mismatch in the impedance within a transmission line or in the load, this high-frequency pulse will be reflected as well as refracted. A behavioral study of this impulse waveform can detect any possible defects or pre-fault as well as post-fault locations due to a mismatch in the total impedance of the circuit. This paper summarized the behavior study and extraction of superimposed impulse waveform with sinusoidal voltage on transmission lines for faults and defects at different locations.

Cross-linked polyethylene (XLPE) is one of the most used insulation materials in the cable manufacturing industry due to its excellent properties compared to other insulating materials. The manufacturing of XLPE cable involves the curing process where the insulation is subjected to a high temperatures and pressures for a certain defined duration in order to ensure the proper crosslinking and thereby enhance the material's performance. In this paper, lab-made XLPE samples are subjected to different curing temperatures (uncured, 150°C, 180°C and 200°C) in order to investigate breakdown characteristics under both AC and DC conditions. A possible optima for temperature, where the insulation is properly cross-linked but not deteriorated, is touched upon briefly. The results, albeit preliminary, will be a good starting step, which will hopefully guide the industry in improving the efficiency and reliability of the cable.

In this article, a novel method to estimate the location of a defect in the semiconducting layer either for insulation or the conductor screen of a cable is proposed using broadband impedance spectroscopy through sweep frequency response analysis. A relationship between the sum of frequencies of zeroes and the electrical parameters of the cable is established, perhaps for the first time in the case of a cable. Transmission line theory and state-space model are used to establish the relationship of zeroes with the propagation constant and electrical parameters of the cable, respectively. Furthermore, an analytical formula is proposed for the estimation of the location of defects of various sizes in the semiconducting layer using the frequency location of zeros and their cumulative sum and product. Both, finite element method (FEM)-based simulations, as well as experiments on a test cable, were performed to validate the proposed formulae.

The article presents an experimental validation of the author’s hypothesis stating the Tx coil antenna, capable of forming a widespread uniform magnetic field, attains constant output current (C-O-C) and constant output voltage (C-O-V). Aiming this, a previously published NUDCT Tx coil antenna was adopted to form a uniform magnetic field. Additionally, with the aid of in-house high-frequency inverters and rectifier circuits, the authors experimentally attempted to prove C-O-C and C-O-V. As a result, this eliminates complex control circuits, higher-order compensation networks, and additional dc-dc converters at the Rx side. Moreover, the Tx coil antenna is fabricated using three different materials to validate the enhancement of dc-dc efficiency by employing low-loss materials without altering the optimized parameters of the Tx coil antenna.

Under diverse loading conditions, high-voltage alternating current (HV-AC) underground polymeric cables exhibit a radial temperature gradient and experience differential thermal stress, resulting in inhomogeneous aging of the polymeric material. Consequently, a differential localized structural alterations occur at different radial positions within the insulation bulk of the cable. To investigate these effects, the authors have examined the cross-linked polyethylene (XLPE) insulation taken from HV-AC cables. Using a lathe machine, samples were extracted and subjected to various tests. The findings revealed significant variations in the morphology of the XLPE layers at different radial positions within the cable insulation bulk. These effects were further investigated by measuring the permittivity of samples extracted from different radial positions within the insulation bulk. The permittivity data is then fitted to field, temperature and radial position dependent equation, and the AC electric field distribution is estimated. The findings are also corroborated by AC breakdown tests.

This paper highlights the problems associated with a prevalent defect in extruded HVDC cables called eccentricity, which refers to an uneven thickness of insulation in the cable cross-section. IEC 62067 specifies an upper limit of 10% on the allowed eccentricity. However, this limit needs to be revised owing to the electro-thermal instability concerns, as discussed in this paper. Based on comprehensive electro-thermal FEM simulations, the authors investigate the effect of eccentricity under different operating conditions of the cable and thereby suggest appropriate revision to the standard.

In this article, a Switched Modular Multi-coil Array transmitter pad integrated with coil RecTenna (SMMART) is designed to present an intelligent wireless drone charging system that improves lateral misalignment tolerance. The resultant optimized design constitutes four independent transmitter modules, wherein each includes four spatially distributed $\mathbf{2\times2}$ array coils. Therefore, the proposed design induces a maximal uniform voltage in the Rx coil region. Moreover, the optimization procedure accounts for the miniaturization of transmitter coil size without compromising the misalignment tolerance by overlapping various transmitter modules. In addition, a novel coil-based detection system for wireless chargeable drone applications is proposed to activate the desired transmitter module based on the position of the receiver coil. The detection system consists of an array of coil rectennas integrated with a switching circuit to reduce the undesired magnetic field, enhancing the link efficiency. The prototype of the charging pad is fabricated using Litz wire, and the S21-based link efficiency is measured using an experimental setup. Besides, the fabricated coil rectenna sensor array system demonstrates a real-application model of the detection system. Hence, the proposed transmitter pad improves lateral misalignment tolerance and is considered a potential wireless drone charging system design.

Inhomogeneous temperature distribution within the bulk of the cable insulation can lead to unexpected conductivity variations at different radial positions of the insulation. Consequently, when estimating the electric field, considering the cable insulation as a homogeneous bulk may not provide an accurate model. In this paper cable insulation is peeled out from 220kV XLPE cable at equidistant radial position from conductor. Volumetric current at 50kv/mm at 40 °C for 1 hour is measured for all layers and conductivity equation is estimated. This conductivity equation is used for estimation of electric field inside the bulk of cable insulation using FEM based COMSOL Multiphysics software. Estimation of electric field based on spatial conductivity has been done and compared with electric field estimated considering conductivity as bulk property of cable insulation.