Underground Cables Research Articles

An Optimized Solution for Fault Detection and Location in Underground Cables Based on Traveling Waves

Faults in the power system affect the reliability, safety, and stability. Power-distribution systems are familiar with the different faults that can damage the overall performance of the entire system, from which they need to be effectively cleared. Underground power systems are more complex and require extra accuracy in fault detection and location for optimum fault management. Slow processing and the unavailability of a protection zone for relay coordination are concerns in fault detection and location, as these reduce the performance of power-protection systems. In this regard, this article proposes an optimized solution for a fault detection and location framework for underground cables based on a discrete wavelet transform (DWT). The proposed model supports area detection, the identification of faulty sections, and fault location. To overcome the abovementioned facts, we optimize the relay coordination for the overcurrent and timing relays. The proposed protection zone has two sequential stages for the current and time at which it optimizes the current and time settings of the connected relays through Newton–Raphson analysis (NRA). Moreover, the traveling times for the DWT are modeled, which relate to the protection zone provided by the relay coordination, and the faulty line that is identified as the relay protection is not overlapped. The model was tested for 132 kV/11 kV and 16-node networks for underground cables, and the obtained results show that the proposed model can detect and locate the cable’s faults speedily, as it detects the fault in 0.01 s, and at the accurate location. MATLAB/Simulink (DigSILENT Toolbox) is used to establish the underground network for fault location and detection.

Muscle Activity And User-perceived Exertion During Immersive Virtual Reality Exergaming Incorporating Adaptive Cable Resistance

INTRODUCTION: Resistance training is often avoided in a wide range of populations due to the uncomfortable feelings of intense exertion. Exergaming, which is defined as the integration of video gameplay into exercise training, has shown the ability to distract users from perceived exertion. PURPOSE: The purpose of this exploratory study was to characterize muscle activation via surface electromyography (sEMG), user-perceived exertion, and enjoyment during a 30-minute session of immersive virtual reality (IVR) cable resistance exergaming. METHODS: Ten healthy, college-aged males completed a signature 30-minute exergaming session using an IVR adaptive cable resistance system that incorporated six traditional compound exercises. Muscle activation (sEMG) was captured during the session with a wearable sEMG system. Rated of Perceived Exertion (RPE), and Physical Activity Enjoyment Scale (PACES) were recorded following the session. RESULTS: The adaptive cable resistance system induced similar activation patterns over time in every exercise (p < 0.001). Pectoralis major showed the highest activation during chest press, deltoids showed the highest activation on overhead press, latissimus dorsi showed the highest activation during lat pulldown and row exercises, hamstrings were the most activated muscles during Romanian deadlift, and glutes showed the highest activity during squats. RPE and PACES mean scores were 14(1) and 4.27(0.38), respectively. CONCLUSIONS: IVR exergaming with resistance cable training provides an enjoyable experience and distracts practitioners from exertion while exercising at a high intensity. Results from this study suggest similar muscle activation responses compared to traditional resistance exercises as demonstrated with prior evidence. This novel form of exercise might have important repercussions for improving health outcomes among those who find it challenging to adhere to and enjoy exercise routines, as well as those with little knowledge on how to progress in their resistance training. Further investigations are needed to explore long-term adaptations and to assess if IVR exergaming has additional benefits compared to traditional resistance training.

FEM-based Arrhenius modeling of the thermal effects of a heating pipeline and pavements on underground power cables

It is well-known that, in thermal aging management of underground power cables, analytical Arrhenius models can include the thermal effect of a heating pipeline on the lifespan of power cables through a rise in the soil temperature and an appropriate ampacity de-rating factor. However, the thermal effect of a pavement on the lifespan of power cables installed below that pavement cannot be taken into account using any de-rating factor. Accordingly, this paper proposes FEM-based Arrhenius models to analyze the thermal effects of one heating pipeline and several different types of pavements on the thermal lifespan of an underground line of 110 kV consisting of cables with cross-linked polyethylene (XLPE) insulation. Each proposed Arrhenius model is created using both IEC 60287 and IEC TR 62095, as well as combining the traditional Arrhenius model with an appropriate FEM-based steady-state thermal model. An experimental background consisting of the existing thermal aging tests with XLPE insulation is also used. Different pavements are represented by different values of thermal and surface radiation properties, namely: thermal conductivity, solar absorptivity, and thermal emissivity. The pavement surface radiation properties are specified within the frames of the most unfavorable summer conditions, and the most common winter conditions. Moreover, different distances between the 110 kV cables and the heating pipeline are considered. Finally, it is found that: the considered thermal effects can shorten the expected total service lifespan of the 110 kV cables in the area adjacent to the heating pipeline by up to 297.5 h; the pavement surface radiation properties do not affect the consumption of total thermal lifespan; as well as the largest consumption of total thermal lifespan occurs when the 110 kV cables are at the smallest distance from the heating pipeline.

An Investigation of Magnetic Field Influence in Underground High Voltage Cable Shields

Magnetic fields and the shielding efficiency of the shields of underground high voltage cables are studied in this paper regarding several shielding configurations and materials. Shielding efficiency and magnetic fields are computed for shields with the same mesh but from different shielding materials, such as aluminum, ferrite, metal, and steel. In order to get the best shield configuration depending on the source characteristics and the material, a conducting ferromagnetic region with various thickness values is considered as shielding. A finite element model is introduced to investigate the influence of the parameters of magnetic fields and the shielding efficiency of underground high voltage cables. Furthermore, the reduction of the magnetic fields with or without shieldings is also presented. The developed method is performed with the magnetic vector potential formulations and validated on a practical problem.

Multi-Layer Model Enabled Fault Location for Underground Cables in MMC-HVDC Grids Considering Distributed and Frequency Dependent Line Parameters

Accurate fault location for underground cables in MMC-HVDC grids reduces the time finding faults as well as the system operational costs. For MMC-HVDC grids, the data window during faults is usually short. During such severe transients, the frequency dependent line parameters of the underground cables have strong influence on the fault location accuracy. In this paper, a novel fault location algorithm for underground cables in MMC-HVDC grids is proposed. First, a multi-layer model for the underground cable using partial differential equations is proposed, which considers the distributed and frequency dependent line parameters in time domain. Afterwards, the numerical finite difference solution of the multi-layer model is proposed to obtain the voltage distributions along the entire cable. Finally, the voltage method is applied to locate faults. Numerical experiments show that the multi-layer model accurately considers the frequency dependency of the cable parameters, and the solution of the model obtains accurate voltage distribution even during system transient. Extensive test cases prove that the proposed algorithm locates faults with less errors than the existing algorithm. The method is also compatible with a relatively low sampling rate (20 kHz) and a short data window (5 ms).

Electromagnetic waves in lossy conductive media: cylindrical and spherical symmetry cases

It was recently demonstrated that surface electromagnetic waves can propagate inside stratified lossy conductive media. Here we consider electromagnetic waves in lossy conductive media in the cylindrical and spherical symmetry cases. We demonstrate that low loss electromagnetic waves may also propagate along cylindrical channels inside lossy media. Applications of these cylindrical waves may include active communication through plasma, search for underground cables, and propagation of electromagnetic signals along bones and nerves inside biological tissues. On the other hand, consideration of the spherical symmetry case indicates the possibility of deeply subwavelength ‘hot spots’ inside highly lossy biological tissues.

Coordinated Reactive Power Control with a Variable Shunt Reactor and an Inverter-Based Wind Power Plant

Underground or submarine cables have a higher capacitance component than overhead lines, and they inject a large amount of capacitive reactive power into the system. A separate reactive power compensation device is required in order for a wind power plant (WPP) connected to the public network with a cable to meet the reactive power requirements required by the grid code. In this paper, a reactive power control using a variable shunt reactor (VSR) was proposed to satisfy the reactive power requirement required by the grid code for a WPP connected to the grid through a cable. The proposed reactive power control method compensates for the capacitive reactive power of the cable by using a VSR, and it follows the reactive power command through the reactive power control of a WPP. In the section where it is difficult to follow the WPP reactive power command only with the reactive power capacity of a WPP due to cable losses or a cable reactive power compensation error of the VSR, the reactive power control is additionally supported through the hysteresis control of the VSR. The proposed method satisfies the grid codes, and it enables fast and accurate reactive power control. The performance of the proposed method was verified through simulation using MATLAB/Simulink.

High voltage direct current transmission cables to help decarbonisation in Europe: Recent achievements and issues

High Voltage Direct Current (HVDC) underground and submarine cables constitute an essential technology for the long-distance transmission of renewable electrical power with low losses, thereby fostering decarbonisation. In the past 2 decades, all this yielded a quasi-exponential rise of HVDC cable systems installed worldwide, but has also made the working conditions of HVDC cables harsher. In this paper, the contribution of HVDC cables to decarbonisation is tackled, with particular reference to the situation in Europe, and a few simple calculations showing in general terms the quantitative contribution provided by HVDC cable systems to decarbonisation are given. Then, the major issues towards long-lasting and reliable HVDC cable systems are summarised briefly, focussing—for the sake of brevity—on the influence of the main HVDC cable technologies, of cable laying environment and of duty service. Some hints are also provided at the chances given by multiterminal HVDC systems.

Power system static and dynamic security studies for the 1st phase of Crete Island Interconnection

The island of Crete is currently served by an autonomous electrical system being fed by oil-fired (Heavy fuel or light Diesel oil) thermal power plants and renewables (wind and PVs). The peak load and annual electric energy consumption are approximately 600 MW and 3 TWh respectively; wind and photovoltaic parks contribute approximately 20% of the electricity needs of the island. Due to the expensive fuel used, the Cretan power system has very high electric energy generation cost compared to the Greek mainland. On the other side the limited size of the system poses severe limitations to the penetration of renewable energy sources, not allowing to further exploit the high wind and solar potential of the island. According to the Ten Year Network Development Plan (TYNDP) of the Greek TSO (Independent Power Transmission Operator S.A. IPTO S.A.), the interconnection of Crete to the mainland Transmission System of Greece will be realized through two links: A 150 kV HVAC link between the Peloponnese and the Crete (Phase I) and a HVDC link connecting the metropolitan area of Athens with Crete (Phase II). The total length of submarine and underground cable of the HVAC link will be approximately 174km; it is at the limits of the AC technology and the longest and deepest worldwide at 150 kV level. A number of studies have been conducted by a joint group of IPTO and Hellenic Electricity Distribution Network Operator (HEDNO) for the design of this interconnection. This paper presents briefly the power system static and dynamic studies conducted for the design of the AC link and its operation. Firstly, the paper presents the main results of the static security study regarding the calculation of the maximum power transfer capability of the link and the selection of the reactive power compensation scheme of the cable. Results from dynamic security analysis studies are also presented. The small-signal stability analysis concludes that a new (intra-area) electromechanical oscillation is introduced to the National System after the interconnection. The damping of the electromechanical oscillations is sufficient; however the operation of power system stabilizers at power plants located both at the mainland and at Crete power system can increase significantly the damping of important oscillation modes. Finally with respect to the risk of loss of synchronism after a significant disturbance in the system of Crete, such as a three-phase fault (“transient stability”)- enough safety margin is estimated by means of Critical Clearing Time calculations.

Harmonic Resonance Characteristic of Large-Scale PV Plant: Modelling, Analysis, and Engineering Case

Harmonic amplification and interaction of the PV plant which contains multiple parallel inverters influence the renewable power generation and operation seriously. In this article, the resonance mechanism and characteristics of a real large-scale PV plant are explored based on its plant-level circuit model. The component and system models are established first. The distribution rules of wideband resonance frequency from the perspective of the point of common coupling (PCC) and the inverter are respectively determined. Two different resonance bands excited by LCL filter and underground cable are further identified. At last, the practical case of harmonic resonance in the studied PV plant is investigated. Both the measured data and the simulation results support the analytical conclusions. This article combines the theoretical study with the engineering practice, which provides beneficial guidance on the resonance prevention.

AC loss and contact resistance in highly flexible rebco cable for fusion applications

High Temperature Superconductor (HTS) materials can operate at higher magnetic fields up to 20 T with high critical current and higher operating temperature, compared to low temperature superconductors (LTS). A Highly Flexible REBCO Cable (HFRC) is introduced at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP); a cabling method that is suitable for REBCO HTS tape having anisotropic material properties in its thin REBCO layer. This type of HTS superconducting cable shows high potential for applications in nuclear fusion. The alternating currents and magnetic fields in tokamak type of fusion magnets, cause AC power losses in such cables, which can provoke instability of the conductor by induced currents and increase the temperature. As a first step in characterizing the electromagnetic (EM) performance of an HFRC cable, the AC loss and contact resistance of the HFRC prototype cable were measured at the University of Twente. The measurements were done in liquid helium (4.2 K) with AC magnetic fields, applied perpendicular to the cable's long axis. The AC loss was measured simultaneously by a calibrated gas flow calorimeter utilizing the helium boil-off method, and by the magnetization method using pick-up coils. For the applied test conditions, no coupling loss could be distinguished as a part of the overall AC loss. It is suggested that this might be explained by the shielding of the conductor interior from the applied magnetic field by the outer tape layer due to the high critical current density of the REBCO tape, leading to a high penetration field.

Automatic Hyperbola Detection and Apex Extraction Using Convolutional Neural Network on GPR Data

Ground Penetrating Radar (GPR) is a non-destructive geophysical method used for subsurface mapping. It is frequently used for detecting buried cylindrical objects such as underground pipes and cables. Buried cylindrical objects show a hyperbolic signal pattern on a radargram. The typical shape of the hyperbolic reflections depends on the depth and material of the buried objects and the surrounding materials. In many cases, detecting buried cylindrical objects is quite a time-consuming task, thus limiting further interpretation procedures. In this paper, we propose a new method for automating hyperbola detection and apex extraction on radargram. Our work consists of two modules that take radargram as input in a form of images. In the first module, we used the Faster-RCNN to extract the hyperbola segments as a set of rectangular boundary boxes. The network was trained using synthetic radargram data simulated by the gprMax software. The second module is to estimate the coordinates of the hyperbola apex using an image processing technique. We had correctly detected all hyperbola on the simulated radargram from the test set. For the test on field radargram, the framework is capable of processing radargram that is similar to the simulated radargram data. The problem with the second module occurs on interference hyperbola as the searching window is disturbed by the noise. Apart from those problems, by using these two modules, the detection of buried cylindrical objects using GPR can be automated with a minimal amount of time.

Effect of silica nanofiller in cross-linked polyethylene as electrical tree growth inhibitor

One of the main phenomena that contributes to the non-success of cable insulation made of cross-linked polyethylene (XLPE) is electrical treeing. To improve the XPLE cable insulation, the use of nanofiller has been introduced. Adding the nanofiller in the based composite offers better cable lifetime and resistance to deal with the cable failure. One of the potential nanofillers that can increase the insulation performance of XLPE cable is silica nanofiller. To this extent, the studies on silica nanofiller in XLPE are focusing on the impulse breakdown strength, dielectric loss, permittivity, space charge, alternating current (AC), and partial discharge. The studies reveal that the dielectric properties of the XLPE nanocomposite have significant improvement. Therefore, this work investigates the effect of various concentrations of silica nanofiller in XLPE composite as electrical tree inhibitor. The concentrations of silica nanofiller in XLPE were 0.25 wt%, 0.5 wt%, 0.75 wt%, 1.0 wt%, 1.25 wt%, 1.5 wt%, and 1.75 wt%. The silica nanofillers have 96%-99% purity, 20-30 nm sizes and the shapes are spherical. As a result, the XLPE composite containing 1.5 wt% silica nanofiller demonstrate higher tree inception voltage and detaining the tree propagation speed, which could be considered as an inhibitor medium of electrical tree growth.

Minimum Voltage-Current Characteristic for Calculating Surge Arrester Energy Dissipation in Temporary Overvoltage Conditions

Abstract--A method is described for estimating required energy capability of surge arresters with respect to temporary overvoltages (TOVs). The method makes use of surge arrester catalogue data on thermal energy rating and TOV capability for estimating minimum voltage-current characteristics suitable for energy calculations by electromagnetic transient simulation tools. The need to recalculate composite TOV events for comparison with TOV capability curves is thereby avoided; this makes the method especially useful in conditions of resonant TOVs comprising harmonics, e.g., from energization of transformers in transmission networks with a large share of underground cables.

Underground Cable Fault Detection Device Using Microcontroller

Abstract: A fault can be defined as any event that interferes with the normal flow of current. Generally, electrical power systems are exposed to the occurrence of any type of contingency, which may be external or internal. Underground cables are commonly used for transmission and distribution of power particularly in cities. Faults in underground cables hamper the continuous supply of power to industrial facilities and households. This paper details different types of faults commonly occur in underground cables and a device has been developed and tested, using ohm’s law principle, for detecting underground faults. This system uses an Arduino microcontroller board and a rectified power supply. Here the current sensing circuits, made with a combination of resistors, are interfaced to Arduino microcontroller board to help of the internal ADC device for providing digital data to the microcontroller representing the cable length in kilometers and displayed on LCD display. Keywords: Underground Cable, Fault Location, Fault Detection, Microcontroller, Power Transmission

The dependence of the internal electrical resistance of the cable rubber rope on the presence of a cable rupture

Problems. The introduction of steel reinforced concrete coatings of structures, in our opinion, is preceded by the development of methods for monitoring the state of cable-stayed ropes - creating safe conditions for long-term operation of structures.&#x0D; The aim of the study. Analytical determination of the dependence of the internal electrical resistance of a cable-stayed rubber cable rope on the presence of a cable rupture.&#x0D; Methods of implementation. To control all cables, the system must provide alternate monitoring of the electrical resistances of the circuits formed by the cables, compare them with reference values, and issue a signal regarding the condition of the rope. It should be designed on the basis of the following data: the type and design of the cable-stayed rope, its length, the number and layout of the cables in the rope, the ability to access one or both of its ends, the electrical properties of the cables and rubber, the resistance values ​​of the cables for all schemes of their determination.&#x0D; Research results. Requirements for the automatic control system of the cable-stayed rubber cord rope. The regularity of the dependence of the electrical resistance of the cable-stayed rope on the burst of an arbitrary cable. Possibility of automatic control of the state of the rubber-cable cable-stayed rope.&#x0D; Conclusions. The results obtained can be considered quite reliable, since the equations obtained on the basis of the fundamental provisions of electrical engineering are obtained analytically in a closed form. Experimental studies have established that the internal electrical resistance of the rope cables depends on its properties and the presence or absence of damage to the cables. The rope includes a number of cables. Any cable can be damaged.

Case Study of Trenchless Technology Around The Globe

Abstract: Trenchless technology is the science of installing, repairing and renewing underground constructions, pipes, and cables that minimize the use of open-cut excavation methods. The use of traditional construction techniques, preferably open-cut construction are being used less because of innovation in trenchless methods. These methods reduce the impact on the environment i.e harmful gas and disruption i.e traffic delays, pedestrian problems, noise problems, and surface issues. This research will describe the advantages of trenchless methods over conventional trenching methods. Keywords: Trenchless technology, Open-cut excavation.

FAULT DETECTION OF UNDERGROUND CABLES THOUGH NODE MCUMODULE USING IOT

Underground cables are vulnerable to a variety of issues due to subsurface settings, wear and tear, rats, and other factors. It is difficult to diagnose the source of the fault, and to examine and correct issues, the entire cable must be removed from the ground. Using an Arduino, the project effort aims to determine the location of a fault in subterranean cable lines from the base station in kilometres. The wire must be examined for defects in order to discover a fault. This prototype employs the concept of Ohms law. The current would fluctuate depending on the fault length of the cable. The suggested method pinpoints the fault's exact location. To ensure correctness, the prototype is built with a series of resistors that indicate cable length in kilometres, and faults are created by a set of switches at every known distance. KEYWORDS : NODE MCU module, cable fault, Arduino, switches

Analytical investigation of the main cable bending stiffness effect on free flexural vibration of suspension bridges with a 3D cable system

This paper proposed a dimensionless continuum model of suspension bridges to comprehensively study the bending stiffness effect of the 3D cable system on the structural free flexural vibration, which has seldom been investigated in previous studies. In this model, coupled differential equations including the cable bending resistance term are derived via the Galerkin method. The equations are then nondimensionalized from a set of key design parameters, including the lateral inclination of hangers. The precision of the model is validated with the finite element (FE) method through an example. Then, parametric comparative studies of the effect under dimensionless parameters are conducted between 3D and 2D cable system suspension bridges. The results show that, the bending stiffness effects of the 3D cable system are more evident on the high order modes and antisymmetric modes of suspension bridges, which is similar with those effects of the 2D cable system. The hanger lateral inclination restrains the effect on the structural frequencies following a relationship of linear negative correlation; when the inclination angle varies from 30 to 60 degrees, the effect ratio of 3D to 2D cable system correspondingly varies from 0.33 to 0.67. Under a given hanger lateral inclination (48.6 degrees) with other identical conditions, the variation trend of the effects on the high order frequencies are similar between 3D and 2D cable systems; the effect value of the 3D cable system is on average 0.625 times that value of the 2D cable system.

An approach to the impedance modelling of low-voltage cables in digital twins

The volatility of distributed production and the uncoordinated charging of electric vehicles cause major challenges in terms of supply reliability and local congestion problems in the distribution networks. In order to tackle these two aspects preventively, digital twin models are introduced to analyse the impacts of these stochastic distributed grid exchangers. Herein, line impedances are a key feature which determines the accuracy of the model. The chosen software environment to set up these digital twins, is based on Carson’s equations which are typically used for overhead high voltage lines. Hence, in this contribution an adapted model of Carson’s equations on low-voltage underground cables at 50 Hz is presented, with the aim to develop a digital twin for analysing the integration of nowadays loads and distributed sources on low voltage distribution systems. Finally, the model will be validated based on realistic grid and smart meter data provided by a distribution system operator.