Underground Cables Research Articles

A Learning-Based Framework for Locating Faults on Power Grid Lines Based on Distortion of Traveling Waves

Accurate measurement of Travelling Waves (TWs) and processing their data in the time and/or frequency domains can provide valuable information about faults in the system. On this basis, this paper presents a Learning-Based Framework (LBF) for locating faults on Overhead Lines (OHLs) and Underground Cables (UGCs) using TWs. The proposed method is single-ended, i.e., it does not require communication and time synchronization, and locates faults based on distortion of the first TW received at the terminal of the line and attenuation of its frequency components. Therefore, in contrast to the majority of existing methods in the literature, differentiating between the reflected waves from the fault point and the remote end is no longer mandatory if only single ended measurements are available. To locate faults, the proposed method trains a Multi-Layer Perceptron (MLP) model based on attenuation of TWs’ frequency components when they travel from their corresponding fault locations to the terminal of the line. Since this attenuation is a function of frequency and travelling distance, a well-trained MLP model can estimate the fault’s location by extracting the frequency components of its first TW using the Fast Fourier Transform (FFT), and by inferring their attenuation pattern. Additionally, the proposed method minimizes the effects of noise and the limited bandwidth of measurement equipment, e.g., Current Transformers (CTs), by considering these factors in the learning process of the MLP model. Simulation results obtained from PSCAD/EMTDC for an OHL and a UGC in CIGRE transmission and distribution benchmark systems corroborate the effectiveness and accuracy of the proposed LBF in locating faults occurred on power grid lines. The results also confirm that the proposed method works independently from fault parameters and system operating conditions.

Statistical Investigation of the Disturbances Affecting the Power Distribution Networks (HTB/HTA) of a Few Source Substations in South-Benin

Power quality is a significant issue that has become increasingly important to both electric power utilities and their customers because of financial losses caused by insufficient. In this work, the Fourier transform (FT) has been exploited for the statistical investigation of the disturbances affecting the electrical distribution networks (HTA) in South-Benin. The data coming from the overhead line disturbances and underground cables, especially from the source substations of MARIA-GLETA, VEDOKO, AKPAKPA, GBEGAMEY and SEME have been treated. These data have been collected and made in our disposal by the Beninese Electricity Energy Company (SBEE) over the period from 2010 to 2017. Harmonic Distortion Rate (TDH) and the Disturbance Rate (D<SUB>R</SUB>) have been used to evaluate the variation coefficient of the different disturbances registered at the each source substation, in order to characterize the harmonic pollution and the reactive power consumption. According to the EN 50160 N standard, the results obtained show that VEDOKO registered 500 to 2000 interruptions of duration between 0.4x10⁵ and 1.8x10⁵ minutes, between 2013 and 2016 especially due to a very critical load shedding. The dominance of the disturbances observed has been due exclusively to the incidents setting off and the load shedding incidents in 2017. 2013 and 2015 have been characterized by the frequent blackouts of long living, and occasion considerable damages, and consequently slow down the economic activities, social and cultural life of consumers.

Mapping the Buried Cable by Ground Penetrating Radar and Gaussian-Process Regression

With the rapid expansion of urban areas and the increasingly use of electricity, the need for locating buried cables is becoming urgent. In this paper, a noval method to locate underground cables based on Ground Penetrating Radar (GPR) and Gaussian-process regression is proposed. Firstly, the coordinate system of the detected area is conducted, and the input and output of locating buried cables are determined. The GPR is moved along the established parallel detection lines, and the hyperbolic signatures generated by buried cables are identified and fitted, thus the positions and depths of some points on the cable could be derived. On the basis of the established coordinate system and the derived points on the cable, the clustering method and cable fitting algorithm based on Gaussian-process regression are proposed to find the most likely locations of the underground cables. Furthermore, the confidence intervals of the cable's locations are also obtained. Both the position and depth noises are taken into account in our method, ensuring the robustness and feasibility in different environments and equipments. Experiments on real-world datasets are conducted, and the obtained results demonstrate the effectiveness of the proposed method.

Research and Design Handle Temperature Camera

Thermal cameras are useful devices that are used in many different situations, such as quality control, system maintenance, structural repair, security, medical, monitoring, treatment and diagnose human health or to research and develop advanced technological components. It provides visual temperature information that cannot be perceived by the human senses. Gade &amp; Moeslund (2014) specified that Thermal cameras are passive sensors that capture the infrared radiation emitted by all objects with a temperature above absolute zero. This type of camera was originally developed as a surveillance and night vision tool for the military, but recently the price has dropped, significantly opening up a broader field of applications. Our study shows With basic functions that can be used such as non-contact body temperature measurement, maintenance, maintenance, quality inspection and repair of electronic, electromechanical, telephone, chip, IC, over temperature detection, electrical system lines, underground cables, recessed walls, utilities, gas leak detection, ventilation furnaces, fireplaces, etc., the device can be a useful and effective civil tool.

Optimal Parameter Estimation of Transmission Line Using Chaotic Initialized Time-Varying PSO Algorithm

Transmission line is a vital part of the power system that connects two major points, the generation, and the distribution. For an efficient design, stable control, and steady operation of the power system, adequate knowledge of the transmission line parameters resistance, inductance, capacitance, and conductance is of great importance. These parameters are essential for transmission network expansion planning in which a new parallel line is needed to be installed due to increased load demand or the overhead line is replaced with an underground cable. This paper presents a method to optimally estimate the parameters using the input-output quantities i.e., voltages, currents, and power factor of the transmission line. The equivalent π-network model is used and the terminal data i.e., sending-end and receiving-end quantities are assumed as available measured data. The parameter estimation problem is converted to an optimization problem by formulating an error-minimizing objective function. An improved particle swarm optimization (PSO) in terms of time-varying control parameters and chaos-based initialization is used to optimally estimate the line parameters. Two cases are considered for parameter estimation, the first case is when the line conductance is neglected and in the second case, the conductance is considered into account. The results obtained by the improved algorithm are compared with the standard version of the algorithm, firefly algorithm and artificial bee colony algorithm for 30 number of trials. It is concluded that the improved algorithm is tremendously sufficient in estimating the line parameters in both cases validated by low error values and statistical analysis, comparatively.

Self-Referencing TDR Dielectric Spectroscopy Using Reflection-Decoupled Analysis With a Mismatched Section

An innovative self-referencing time-domain reflectometry (TDR) dielectric spectroscopy method is introduced. The method extracts the first reflection from a mismatched section (MS) immediately before the sensing section (SS) to capture the source characteristics and effect of leading sections. A reflection-decoupled analysis (RDA) is derived to characterize the complex dielectric permittivity (CDP) in the ss. Conventional time-domain spectroscopy (TDS) offers a more cost-effective alternative to frequency-domain methods, but its accuracy may suffer from input function variation, system mismatches, and probe design restrictions. RDA with MS approach provides an efficient, robust, and flexible dielectric spectroscopy technique including its calibration, which inherits all advantages of conventional TDS while using more economic TDR device and more flexible probe design. It adopts a nonconductive and nondispersive MS to serve as a reflector for reliable reference source directly embedded in a single TDR signal. Spectral ratios between the reflection from MS and all other reflections from the SS are experimentally determined and matched to the RDA-derived values as a function of CDP. RDA is inherently independent of source function, instrument mismatch, and cable resistance. There are only four frequency-independent system parameters that can be easily calibrated once and for all using a measurement of well-known material. The method is presented in a general framework without major restrictive assumptions, which explicitly expresses all probe parameters, allowing greater flexibility in probe design (e.g., geometric impedance, probe length, and end condition). Robustness of RDA was verified by numerical and experimental investigations using eight materials of different dielectric characteristics.

The Mechanical Behavior of Taper Pipe Threads by Three-dimensional Finite Element Analysis

Taper pipe threads are widely used as fastening parts for connecting pipes through which water, gas, hydraulic oil, etc. flow. It is also widely used in underground conduit facilities to protect underground communication cables from external loads and fluids. One of its characteristics is its high tightness, but there have been reports of leaks and damage due to strong external forces and repeated loads at the time of earthquakes and under even normal use conditions. However, since the mechanical behavior of tapered pipe screws is more complicated than that of ordinary fastening bolts, it is difficult to perform a highly accurate analysis. Therefore, in this study, in order to clarify the mechanical behavior of taper pipe threads, we created a three-dimensional analysis model of hexahedral elements that faithfully reproduces the shape of taper pipe threads, and quantitatively evaluated the effects of parameters such as pipe thickness, coefficient of friction, and number of screwing threads on resistance to external forces. The purpose is to clarify the mechanical properties systematically, and we have elucidated the trends of the parameters on the stress amplitude in three different cyclic load modes.

Muscle Activity and User-Perceived Exertion During Immersive Virtual Reality Exergaming Incorporating an Adaptive Cable Resistance System

Muscle Activity and User-Perceived Exertion During Immersive Virtual Reality Exergaming Incorporating an Adaptive Cable Resistance System

Finite Element Analysis of Electric Field Distribution for 115-kV Underground Power Transmission Systems

A penetration of an electric field intensity generated by an underground cable and a detailed model for demonstrating the actual characteristics are still a challenge. Hence, this article has proposed a mathematical model for diagnosing the electric field intensity of the 115 kV underground power cable, using the 3D finite element method to simulate the electric field while the 115 kV underground cable is available. The proposed finite element method-based 3-D model utilizes a linear sub-derivative equation method, which consists of the weighted residuals and the Galerkin’s methods. The flat and the trefoil formations are considered for the modeling and the simulations of the electric field distributions using the proposed 3-D finite element method. The simulated results demonstrate that the proposed method can reveal the graphical electric field distribution in 3-D around the 115 kV underground cables with detailed characteristics. Moreover, the electric field distributions using the proposed model at various underground depths are demonstrated in comparison between the flat and the trefoil formations. Thus, the proposed method can demonstrate the actual characteristics of the underground cable and the cable arrangement penetration at the various formations.

Surge analysis on wind farm considering lightning strike to multi-blade

The protection of the wind turbines is one of the significant problems, especially as lightning strikes the blades. In this paper, the authors bring forward a model in which nine interconnected wind turbines are connected to the infinitive bus by underground cables. When the blades are struck, for detailed investigation, all the cables inside the wind turbine and underground cables, tower, blades, and other equipment of wind turbine need to be designed in transient mode. Accordingly, the grounding system is also considered by the time-domain model, in which transient grounding resistance behavior is based upon the frequency-dependent model. For this purpose, the EMTP.rv is employed to study the transient behavior of the wind farm when the blades are struck. Eventually, by studying the residual voltage and discharged current in medium voltage surge arrester (MVSA) when lightning strikes WT, the energy absorbed by the MVSA is calculated and employed to evaluate the wind farm resilience against a different type of lightning. As a result, a new approach can be advised for the protection of wind farms against lightning by investigating the energy absorbed by MVSA.

Enhancement of the thermal analysis of harmonics impacts on low voltage underground power cables capacity

This article investigates the harmonic impacts on the underground low voltage cables by using new algorithm. The heating of cables by harmonics may lead to form dry zones around the cables causing insulation failure. De-rating factors due to the influence of the load harmonics for different soil types as back-fill materials are presented. The de-rating factors are calculated for different typical non-sinusoidal current loads with different harmonic order ingredients. The influences of the harmonics in the cable current and also the effect of the dry zone formation in the soil surrounding the cable on the cable capacity and its temperature rise are investigated. New thermal model of three-cores with a neutral low voltage cable that is usually used in low voltage distribution circuits is considered. The proposed technique is based on the heat balance at any node of the cable thermal equivalent circuit. The influences of the neutral conductor area of low voltage cable, on the cable conductor's temperature and cable current are investigated. One of the advantages of the proposed method is that different percentages of harmonics can be considered for each phase separately and the mutual heating between the three phases and neutral cable conductors is considered. De-rating factors due to the harmonic influence on the cable buried in different soil types with and without dry zone formation in the soil surrounding the cable are presented.

Evolution of Temperature Field around Underground Power Cable for Static and Cyclic Heating

Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the conductor, which depends on the surrounding soils’ heat transfer capacity or the thermal conductivity. In the past, numerical and theoretical studies have been conducted based on the mechanistic heat and mass transfer model. However, limited experimental evidence has been provided. Therefore, in this study, we performed a series of experiments for static and cyclic thermal loads with a cylindrical heater embedded in the sand. The results suggest thermal charging of the surrounding dry sand and natural convection within the wet sand. A comparison of heat transfer for dry, unsaturated and fully saturated sand is presented with graphs and colour maps which provide valuable information and insight of heat and mass transfer around an underground power cable. Furthermore, the measurements of thermal conductivity against density, moisture and temperature are presented showing positive nonlinear dependence.

Time-Domain Pulse Waveform Correction for Pulsed Electric Field Measurement in Microwave Cable with Frequency-Dependent Loss

This paper presents a method that corrects pulse waveforms distorted by the frequency-dependent loss of microwave cables in measuring pulsed electric fields (PEFs). Because the distortion resulting from the microwave cable disrupts accurate PEF measurements, the distorted pulse should be corrected for precise PEF effect testing. The proposed correction method is achieved by a transfer function that is determined by ABCD parameters calculated from the scattering parameters of the cable. A 10-m microwave cable is tested to validate the proposed method, where the input pulse is a 2-ns sine pulse of a single cycle. Here, the output pulse, scattering parameters, and cable resistance are measured. These measurement results are used to represent the transfer function in MATLAB for the proposed correction method. The test results show that the corrected pulse obtained from the transfer function has an error of 4.5% in the peak-to-peak voltage and an error of 0.8% in the bipolar pulse width compared to the reference input pulse. The errors of PEF measurement decrease dramatically by using the proposed correction method. Moreover, the correction method is validated for various pulse durations, pulse shapes, and cable types.

Evaluation of the effect of structural defects in the heat-shrink cable terminal on electric field distribution

Cable terminals are used for the connection of high voltage underground cables to busbars and transmission lines. Various defects may occur in cable terminals used as Heat-Shrink or Cold-Shrink. As a result of these defects, fires and long-term power outages may occur due to the breakdown of the cable terminal depending on partial discharge. Consequently, human life losses and economic losses are inevitable. In this study, a heat-shrink cable terminal with 36 kV phase-to-phase operating voltage randomly failed while measuring power quality parameters in the field is examined. In this context, it is aimed to examine the root causes of the failure in the field with the finite element method according to different design and structural defect situations. For this purpose, the cable terminal was modeled in real scale in Ansys Electronics Suite finite element software in line with the data received from the manufacturer. According to the analysis results, especially in case of peeling the entire outer semiconductor layer on the XLPE and partial peeling of the outer semiconductor layer on XLPE increases electric field significantly compared to the reference design. In addition, the thickness and relative permittivity changes of the critical elements used in the cable terminal affect the electric field distribution. According to the results of the analysis performed, the defect situations that could be the root cause of the failure was determined. Also, the effect of other defective situations was understood and reliability analysis was made.

Identification of Fault in Invisible Underground Broken Transmission Lines

ABSTRACT The underground electricity distribution cables are subjected to stress and pressure as they are laid underneath the earth. Due to many factors, these cables create different types of faults that include short circuits. If these faults are not addressed, the power supply is disrupted and resulting in permanent damage. To deal with faults in underground cables, a device has been devised that includes detection of underground broken wires using an android application. The suggested approach measures the electric field around the underground wire. This approach differentiates the short circuit fault from other kinds of faults in underground cables. Only methods for detecting short circuit errors are considered in standard fault detection techniques. The proposed system makes use of low-cost electronic devices that are simple to construct. As a result, the proposed underground fault detection product provides a low-cost optimization solution to locate short-circuit defects.

Heat Dissipation in Variable Underground Power Cable Beddings: Experiences from a Real Scale Field Experiment

To prevent accelerated thermal aging or insulation faults in cable systems due to overheating, the current carrying capacity is usually limited by specific conductor temperatures. As the heat produced during the operation of underground cables has to be dissipated to the environment, the actual current carrying capacity of a power cable system is primarily dependent on the thermal properties of the surrounding porous bedding material and soil. To investigate the heat dissipation processes around buried power cables of real scale and with realistic electric loading, a field experiment consisting of a main field with various cable configurations, laid in four different bedding materials, and a side field with additional cable trenches for thermally enhanced bedding materials and protection pipe systems was planned and constructed. The experimental results present the strong influences of the different bedding materials on the maximum cable ampacity. Alongside the importance of the basic thermal properties, the influence of the bedding’s hydraulic properties, especially on the drying and rewetting effects, were observed. Furthermore, an increase in ampacity between 25% and 35% was determined for a cable system in a duct filled with an artificial grouting material compared to a common air-filled ducted system.

Analysis of Transient Operating Characteristics of the 10 Kv Tri-Axial HTS Cable Under Fault Current

The Tri-axial high temperature superconducting (HTS) cable usually subjects to the impact of the fault currents in the power system. During the fault, a large amount of the Joule heat is generated, which may be damage cable. In this paper, an analysis model of electromagnetic thermal transient characteristics of the 10 kV/1 kA cable is built. The transient characteristics of the HTS cable are analyzed under a fault current of 15 kA rms lasting 0.14 s, and the current, resistance and temperature of the HTS cable are obtained. The maximum temperature of the HTS cable is 153.1 K under fault current. Meanwhile, the safe operating range of the HTS cable under the fault current of 15 kA to 25 kA is obtained. the analysis results will provide the theoretical basis for the quench protection and relay protection strategy of the tri-axial HTS cable in the Grid.

A Bayesian Inference Reliability Evaluation on the Corrosion-Affected Underground High-Voltage Power Grid

The underground high-voltage power transmission cables are high value engineering assets that suffer from multiple deteriorations through-out life cycles. Recent studies identified a new failure mode – the pitting corrosion deterioration on the layer of phosphor bronze reinforcing tape, which protects the oil-filled power transmission cables from oil leakage due to deterioration of the leads heath. Two models estimating the phosphor bronze tape life were established separately in this study. The first model, based on mathematical fitting, is generated using a replacement priority model from the power supply industry. This is considered as an empirical-based model. The second model, based on the corrosion fatigue mechanism, utilizes the information of the pit depth distribution and the concept of pit-to-crack transfer probability. The Bayesian inference approach is the conjunction algorithm to update the existing probability of failure (PoF) model with the newly identified failure modes. Through this algorithm, the integrated PoF model contains a more comprehensive background information while maintaining the empirical knowledge on the engineering assets’ performance.

Calculation Method of Allowable Continuous Current for Direct Burial Laying HVDC Underground Cable

The calculation of the continuous allowable current of an underground cable is determined by various characteristics. To calculate the allowable current in cables with alternating magnetic fields such as AC, special phenomena such as the proximity effect and skin effect must be applied. However, there are no standards or research related to the calculation of the continuous allowable current of a DC power cable that does not have an alternating magnetic field. In this paper, a quantitative DC cable continuous allowable current calculation formula of direct burial laying was derived by applying the existing AC cable continuous allowable current calculation method to the DC system. We developed a calculation tool that can calculate the continuous allowable current of DC cables using the derived formula. Assuming the cable conditions (cable specification, laying conditions, soil characteristics, arrangement, and number of strands, etc.), a continuous allowable current simulation of DC cables was performed. In addition, the level of contribution to the continuous allowable current value was analyzed by classifying the parameter categories into major and minor factors in the order of influence on the allowable current among the determined calculated parameters. As a result, the effectiveness of the DC cable continuous allowable current calculation tool derived by performing the allowable current calculation simulation was evaluated, and the allowable current calculation method of the HVDC cable was established.

Investigation and life expectancy prediction on poly(ether-ether-ketone) cables for thermo-oxidative aging in containment dome of nuclear power plant

As a special engineering material, poly(ether-ether-ketone) (PEEK) wires and cables are widely applied in the containment vessel of nuclear power plant and vulnerable to long-term cumulative effects of multiple complex factors. Wherein, thermo-oxidative aging in high temperature environment for a long time is the key factor to lead to the degradation even failure of PEEK cables. Therefore, in this work, PEEK cables were subjected to thermo-oxidative aging for different times at 310 °C and the effects on the physicochemical properties of PEEK were investigated. Furthermore, the aging life expectancy of PEEK cables was effectively predicted by the innovative artificial accelerated aging model with breaking elongation as evaluation parameter. The results revealed the thermal stability and crystallinity of PEEK samples declined significantly with the extension of aging time. Prolonged thermo-oxidative aging can accelerate the oxidation decomposition and change the sample morphologies. Moreover, the scratch resistance and bending strength of PEEK cables were significantly weakened after 480 h aging. The final prediction suggested that the service life expectancy of PEEK cable samples can reach 73 years at the working temperature of 90 °C.