Cable Safety Research Articles

Research on Improving the Working Efficiency of Hydraulic Jet Submarine Cable Laying Machine

The anchoring and hooking of ships, bedrock friction and biological corrosion threaten the safety and stability of submarine cables. A hydraulic jet submarine cable laying machine manages to bury the submarine cables deep into the seabed, and effectively reduces the occurrence of external damage to the submarine cables. This machine uses a hydraulic jet system to realize trenching on the seabed. However, the hydraulic jet submarine cable laying machine has complicated operation and high power consumption with high requirements on the mother ship, and it is not yet the mainstream trenching method. In this paper, a mathematical model for the hydraulic jet nozzle of the submarine cable laying machine is established, and parameters that affect the trenching efficiency are studied. The effects of jet target distance, flow, angle and nozzle spacing on the working efficiency of the burying machine are analyzed by setting up a double-nozzle model. The results of the theory, numerical simulation and experiment show that the operational efficiency of the hydraulic jet submarine cable laying machine can be distinctly improved by setting proper jet conditions and parameters.

Feasibility study for online assessment on fatigue failure of aluminum cable steel reinforced conductors based on DC resistance measurement method

AbstractThe strength of aluminum cable steel reinforced (ACSR) is an important index of loading capacity and safety of cables and will decrease with fatigue damage. However, the strength of ACSR used in transmission lines would be difficultly measured online. Hence the objective of this work is to investigate online measurement parameters employed to characterize fatigue damage of transmission lines. The resistance and strength characteristics of ACSR conductors in long‐term service were experimental studied; it revealed that strength loss rate is positively correlated with DC resistance growth rate. Then the DC resistance growth rate may be used as a fatigue damage evaluation index. Although the DC resistance of transmission lines is difficultly measured online, a resistance and inductance (RL) distributed parameter model simplified and an online measurement scheme were proposed. The simulation and experimental results showed that the DC resistance can be effectively and accurately measured online.

The Intelligent Operation and Maintenance Management System for Offshore Wind Farms

Introduction Aiming at the operation & maintenance and safety management of offshore wind farm， the intelligent operation and maintenance management system for offshore wind farms is proposed. Method Through the intelligent dispatching system of offshore wind power， multi-source tracking and boundary warning system of offshore wind power radar， and operation supervision system of offshore wind farm wind turbine platform， the intelligent operation and maintenance management system of offshore wind farm was built. Result Through the offshore wind power intelligent dispatching system of the onshore centralized control center， personnel safety management and ship dispatching can be realized. Through the offshore wind power radar multi-source tracking and boundary warning system， the full-range tracking of ships in the ocean area is realized， and the safety of the wind turbines and submarine cables of the offshore wind farm can be ensured. Through the wind turbine platform's offshore wind farm fan platform operation supervision system， the comprehensive management of wind turbine operators on the wind turbine platform can be assured. Conclusion Therefore， it can realize the overall management of personnel， ships and wind turbines in offshore wind farms， it effectively ensures the safety management of personnel and ship scheduling， improves the safety of wind turbines and submarine cables of offshore wind farms， and realizes the intelligent operation and maintenance efficiency of offshore wind farms， which is expected to be applied and promoted in the project.

RETRACTED ARTICLE: Monitoring method based on GIS for submarine cable fault data

With the growth and advancement of the times, people have more and more means of obtaining knowledge. In order to further increase the efficiency of information transmission and energy transport, people have started to lay cables on the seabed. The region of the sea is huge. Cable laying wi ll provide people with wider networks of information transmission and space. Various factors are unpredictable when laying submarine cables, making the precise work more complicated. It takes a lot of time and expense to successfully install the submarine cable, so it is important to ensure its safe operation. Combining the construction of submarine cables with geographic information systems may rely on visualization methods to combine geography and seabed map information and provide intuitive data for people to understand the situation of submarine cables. In order to minimize the uncertainty created by the U-boat environment for cable safety, this article incorporates knowledge of geographic information systems and uses electronic maps to detect the conditions of the U-boat in real time, and designs a device that can control U-boat cable accidents and provides cable security assistance.

Probabilistic Assessment of the Safety of Main Cables for Long‐Span Suspension Bridges considering Corrosion Effects

This paper presents a reliability analysis to assess the safety of corroded main cables of a long‐span suspension bridge. A multiscale probability model was established for the resistance of the main cables considering the length effect and the Daniels effect. Corrosion effects were considered in the wire scale by relating the test results from accelerated corrosion tests to the corrosion stages and in the cable scale by adopting a corrosion stage distribution of the main cable section in NCHRP Report 534. The load effects of temperature, wind load, and traffic load were obtained by solving a finite element model with inputs from in‐service monitoring data. The so‐obtained reliability index of the main cables reduces significantly after operation for over 50 years and falls below the design target value due to corrosion effects on the mechanical properties of the steel wire. Multiple measures should be taken to delay the corrosion effects and ensure the safety of the main cables in the design service life.

A Double-Terminal Traveling-Wave-Based Method Using Novel Noncontact Sensors for Fault Location in Transmission Cable Lines

The burgeoning demand for enhanced power-system safety means that there is increased attention on technologies for the detection and location of cable faults. The double-terminal fault location method, which senses a fault current using a current transformer (CT), is the most effective and widely applied method in industrial practice. However, CT sensors may suffer from magnetic saturation when exposed to a high fault current, resulting in significant location errors, and their sensitivity cannot be adjusted. To address this problem, this paper describes an improved method for the acquisition of fault signal and the identification of fault-wave arrival time in power cables. First, a novel noncontact sensor (NCS) is developed for the detection of electric fields, and its sensitivity-adjustment curves are obtained by theoretical calculation and simulation. Then, based on feedback variational mode decomposition (FVMD) and the Wigner-Ville distribution (WVD), an improved method (the FVMD + WVD method) for the identification of fault-wave arrival time is devised, and its efficacy and accuracy are verified by simulations in Power Systems Computer-Aided Design/Electromagnetic Transients including DC (PSCAD/EMTDC) software. Finally, the fault-wave arrival-time detection performance of the NCS is examined in a series of on-site DC and AC experiments based on damped AC technology. The results show that the NCS exhibits feasible and effective performance, and that its response can be appropriately tuned based on its sensitivity-adjustment curves. The FVMD + WVD method is more accurate than several other current methods, as its error is only 0.48%, and thus this method enables the practical location of cable faults. In sum, these findings demonstrate that the NCS and the FVMD + WVD method comprise an improved system for the detection and location of cable faults, which will enhance cable safety in power systems.

Numerical and physical modeling of submarine telecommunication cables subjected to abrupt lateral seabed movements

Submarine telecommunication cables, which carry about 99% of international telecommunications, are usually buried shallowly beneath seabed and vulnerable to seabed movements. In recent years, many submarine cable damages have been observed when significant lateral seabed movements occur due to geohazards, e.g., offsets of strike-slip faults and submarine landslides. However, research on the interaction between submarine telecommunication cables and lateral seabed movements is limited. There is no existing method for evaluating the cable safety when subjected to lateral seabed movements. This paper aims to carry out finite element (FE) analysis and physical modeling to investigate the responses of submarine telecommunication cables to lateral seabed movements. A FE model is developed and validated by full-scale physical test results. After validation of the FE model, a series of parametric studies is performed covering typical ranges of soil properties, cable burial depths, cable characteristics and seabed movement characteristics. The parametric study results are summarized in a dimensionless plot, followed by a regression analysis. A simple but effective formula is proposed to predict the maximum cable strains induced by lateral seabed movements. The dominant parameters that control submarine cable responses are identified and incorporated into the formula. Safety criteria for submarine telecommunication cables are also proposed for evaluating the cable safety when subjected to lateral seabed movements.

Research on Automatic Cable Monitoring System Based on Vibration Fibber Optic Sensor Technology

To ensure the safety of power cables, temperature monitoring of power cables is critical. In view of the shortcomings of some optical fibre measurement products, a long-distance distributed optical fibre sensor is proposed, which has the advantages of high measurement sensitivity, fast response speed, low false alarm rate, large measurement length, and stable operation. The distributed optical fibre vibration sensing measurement equipment is used to monitor the vibration signals along the cable in real time, and the signal changes before and after the breakdown fault are visually displayed by the patio-temporal spectrum diagram, and the vibration signal of the breakdown point is analysed in time and frequency. The performance of the system was tested, and the experiment verified that the temperature measurement accuracy error range of the temperature measurement system is about ± 5 °C, and it has good stability. At the same time, the positioning accuracy is very high, and the fault point can be accurately located. This can avoid the occurrence of cable accidents.

Evaluation of Anchor Penetration Depth based on Numerical Analysis for Burial Protection Method of Submarine Cables

Submarine cables are installed and operated for the stable power supply of island regions, and feature protective measures to counter marine hazard factors. With regard to the protection techniques to prevent damage to submarine cables, the method of digging and embedding the submarine ground is applied the most. However, since there are no design criteria and techniques for such protection facilities, the burial depth of the submarine ground has been calculated only qualitatively and empirically after an ocean survey is conducted. Such an imperfect method has led to assorted damages to submarine cables. Therefore, in this study, to ensure the safety of submarine cables from marine hazard factors, the three-dimensional dynamic interaction analysis model was established for the ship anchor and ground, and the penetration depth of this anchor was calculated through numerical analysis for the burial protection method. These results were compared and evaluated with the results of the full scale test for anchoring and dragging anchor. As a result, the error rate(average) of the anchor penetration depth through the numerical analysis and test was 12.2% in the ground conditions of sand, clay and multi(clay/sand) layers. This error rate was analyzed to be caused by various uncertainties in the test, such as the dynamic impact of the anchor and ground conditions, and the numerical analysis was evaluated to ensure sufficient reliability. The results of this study are expected to be useful in the burial depth calculation of the burial protection method to ensure the safety of submarine cables.

R-DTS With Heat Transfer Functional Model for Perceiving the Surrounding Temperature

In the field of temperature safety monitoring, it is important to quickly locate the position of temperature anomalies and start to alarm. The multimode fiber (MMF) has a certain temperature hysteresis effect when detecting the surrounding temperature along the sensing fiber, it deteriorates the warning-time of Raman distributed temperature sensor (R-DTS). This paper proposed and experimentally demonstrated an R-DTS with heat transfer functional model to perceive the surrounding temperature in advance. The temperature hysteresis effect of MMF cable in different temperature conditions are studied experimentally. The experimental results show that the temperature change rate of MMF and the surrounding temperature difference maintains a linear relationship after fitting. And this fitting relationship is used to perceive the surrounding temperature anomalies along the MMF for R-DTS system. The experimental results indicate that the warning-time of R-DTS can optimize from 23.4 s to 1.3 s at the temperature condition with 60 °C. It proves that this analytical model of the heat transfer function model can quickly perceive the environment temperature anomalies to avoid the temperature hysteresis effect of MMF at the difference temperature conditions. The research content can be applied in the temperature safety monitoring with high requirements for early-warning time, such as fire monitoring, power cable safety monitoring, and gas pipeline leakage detection.

Corrosion fatigue analysis of stay cables under combined loads of random traffic and wind

After the failure of their protection system, stay cables may subject to environmental corrosion and fatigue loading simultaneously. To study the cable safety during the bridge service life, a general framework was proposed in this paper to estimate the corrosion fatigue life of stay cables under the combined action of random traffic and wind. A simplified approach integrated with the wind-vehicle-bridge system was first introduced to calculate the stress time histories of the stay cables. Based on the traffic data and wind records at the bridge site, the procedure to predict the stress ranges of bridges in service was applied to the North Channel Bridge (NCB) of Hangzhou Bay Bridge as an example and the most critical stay cable was determined. The time-variant corrosion fatigue model of the stay cable was then established considering the deterioration of the steel wires and the corrosion distribution inside the cable. Three levels of corrosion rates (low, medium, and high) were also defined in the model for different environmental conditions, and the corrosion fatigue analysis of the stay cable was finally conducted. The results show that the coupled effects of corrosion and fatigue greatly reduce the lifetime of the wire, and the fatigue resistance of the stay cable in the bridge service life is insufficient under certain corrosion rates.

Operation of cable lines under fire conditions

Branched cable communications are carriers of fire load, they are tracks along which fire spreads in buildings and structures. Therefore, currently, fire safety of cables is one of the most important tasks of the cable industry. The spread of flames in vertical bunch wiring depends on the following factors: the amount of combustible material that is exposed to high temperatures, geometric shapes of cables and their mutual location when laying, the ignition temperature of gases emitted by cables, the volume of combustible gases emitted by cables at a certain elevated temperature, the room capacity and volume of air passing through the cable structure, cable devices. Analysis of regulatory documents revealed some key differences in the methodology of standards. It was found that the spread of fire is not only affected by the volume of laid cables, but also by their mutual placement in space. A direct correlation was found between the influence of the crosssection of the cable core and preservation of the cable line in case of fire. Parameters were determined for the preservation of serviceability under fire exposure in the case of bunch and in the case of single wiring. It has been determined that it is impossible to spread the results of fire tests in case of single wiring in accordance with GOST IEC 60331-21-2011 and in case of bunch wiring in accordance with GOST IEC 60332-3-22-2011 to the results of tests in accordance with GOST R 53316-2009 for the preservation of operability of cable lines. The parameters of fire resistance and operability of cable products under the influence of flame depending on the type of cables and the method of their installation have been determined.

A Proposed Terminal-Ground EMI Filter for Reduction of Conducted Emissions Considering Cable Radiation and Safety

This article proposes an optimal design of a terminal-ground electromagnetic interference filter (TGEF) for reduction of common-mode (CM) conducted emissions (CEs) with considering cable radiations and safety. The TGEF is free from risks of magnetic saturation and heat problem. In experimental tests with a 3.3-kW air conditioner system, a prototype TGEF well reduced low-frequency CM CE noises, but increased disturbance power (DP) due to cable radiations. To investigate the principle of cable radiations, the impedance and parameters in the DP measurement setup are extracted by measurements using a vector network analyzer and validated with full-wave simulations. The effects of the TGEF on total CM DP currents at power cables are also experimentally demonstrated and modeled in simulations. Based on the analysis of DP measurement environments, a quantitative guideline for a TGEF design was proposed without increasing cable radiations while maintaining CE noise attenuation performances. The performances of the optimized TGEF are then validated by CE and DP measurements in the real product system. Moreover, safety of the optimized TGEF in a ground-fault condition was experimentally confirmed.

DETERMINATION OF THE QUANTITY OF COMBUSTIBLE MATERIAL IN CABLE PRODUCTS IN THE PROCESS OF FIRE SAFETY TESTING

Introduction. In order to protect objects from dangerous manifestations of fire of cable products, electrical lines are designed and projected in accordance with the fire-protection requirements and the normative documents. Purpose. The purpose of this article is to analyze this problem in several areas concerning the situation with a systematic approach to the technical regulation in Ukraine of such a sector of fire safety as the requirements for cable-wiring lines. Methods. Methods of research: calculations using a mathematical model; comparison of the results of the calculation, forecasting of the boundary parameters of the technical condition and monitoring of the cable material properties; examination, qualification, definition of indicators of fire safety of cables and wires in the composition of the electrical grids of buildings, structures, foundations and metal structures, taking into account laying conditions. Different methods for volume and mass calculating, fire tests of electrical and fiber optic cables were applicated. Tests of vertically arranged wires or cables laid in beams on the vertical propagation of the flame (Category A F / R, Category A, Category B) were conducted. Results. The experimental study of the installation parameters test and indicators of fire safety for cable-wiring products in their vertical laying that reduce the overall fire safety level of facility electric power operation were conducted. Critical analysis of the current state of development was done. The basis of the fire safety requirements for standardization of cable lines were formulated. The measures for testing methods implementation with description of these methods were proposed. Conclusion. Determination of the combustible material quantity by volume and by mass is not regulated in the current normative documents on fire safety, although this criterion is often used precisely when establishing requirements for fire safety: to buildings, cable installations, to the installation of fire automatics systems and to others. A method for calculating the volume of combustible material for determining the fire risk of cable-conductive products is proposed. The method can be used during designing of wiring lines and during their exploitation. Experimental researches of fire hazard indicators of cable-wiring products were conducted; their group of flame distribution was installed. The method of determining the quantity of combustible material by volume, by mass and with testing of mass loss of combustible material was applied.

Parametric study on cable safety of cable-stayed bridge considering ultimate and fatigue limit states

Parametric study on cable safety of cable-stayed bridge considering ultimate and fatigue limit states

Research on the Method of Predicting Corrosion width of Cables Based on the Spontaneous Magnetic Flux Leakage.

The detection of cable corrosion is of great significance to the evaluation of cable safety performance. Based on the principle of spontaneous magnetic flux leakage (SMFL), a new method for predicting the corrosion width of cables is proposed. In this paper, in order to quantify the width of corrosion, the parameter about intersecting point distance between curves of magnetic flux component of x direction at different lift off heights (Dx) is proposed by establishing the theoretical model of the magnetic dipole of the rectangular corrosion defect. The MATLAB software was used to analyze the influencing factors of Dx. The results indicate that there exists an obvious linear relationship between the Dx and the y (lift off height), and the Dx–y curves converge to near the true corrosion width when y = 0. The 1/4 and 3/4 quantiles of the Dx–y image were used for linear fitting, which the intercept of the fitting equation was used to represent the predicted corrosion width. After the experimental study on the corrosion width detection for the parallel steel wire and steel strand, it is found that this method can effectively improve the detection accuracy, which plays an important role in cable safety assessment.

Performance of Cross-linked Polyethylene Insulated Cable based on Detection of High Voltage Electric Field

High voltage direct current transmission has been widely used in long-distance power transmission because of its advantages such as low loss and large throughput. The safety of cable is very important in the long-distance transmission process. Cross-linked polyethylene insulated cable has the advantages of simple manufacture, good heat resistance and easy installation; therefore it has been widely used in long-distance power transmission. In this study, conductance, dielectric and voltage withstanding performance of the insulating layers of cross-linked polyethylene cables with working voltage of 220 kV which was never used and has been used for 2, 4, 6 and 8 years were tested by various evaluation methods. The conductivity of the insulating layers was affected by temperature only under high and low electric field intensities and was affected by temperature and electric field strength under middle electric field intensity. Dielectric loss factor could reflect dielectric properties of materials; the larger the dielectric loss factor, the poorer the performance. The dielectric loss factor decreased with the increase of applied electric field frequency and increased with the increase of service years. Breakdown electric field strength could reflect voltage resistance of materials; the larger the breakdown electric field strength, the better the performance. The breakdown electric field strength was inversely proportional to the service years of the insulating layer, and the decrease amplitude increased significantly when the service time exceeded 2 years. In summary, cross-linked polyethylene insulated material satisfies the safety requirement of high voltage direct current transmission and can be used for manufacturing long-distance transmission cables.

Performance of Cross-Linked Polyethylene Insulated Cable Based on Detection of High Voltage Electric Field

High voltage direct current transmission has been widely used in long-distance power transmission because of its advantages such as low loss and large throughput. The safety of cable is very important in the long-distance transmission process. Cross-linked polyethylene insulated cable has the advantages of simple manufacture, good heat resistance and easy installation; therefore it has been widely used in long-distance power transmission. In this study, conductance, dielectric and voltage withstanding performance of the insulating layers of cross-linked polyethylene cables with working voltage of 220 kV which was never used and has been used for 2, 4, 6 and 8 years were tested by various evaluation methods. The conductivity of the insulating layers was affected by temperature only under high and low electric field intensities and was affected by temperature and electric field strength under middle electric field intensity. Dielectric loss factor could reflect dielectric properties of materials; the larger the dielectric loss factor, the poorer the performance. The dielectric loss factor decreased with the increase of applied electric field frequency and increased with the increase of service years. Breakdown electric field strength could reflect voltage resistance of materials; the larger the breakdown electric field strength, the better the performance. The breakdown electric field strength was inversely proportional to the service years of the insulating layer, and the decrease amplitude increased significantly when the service time exceeded 2 years. In summary, cross-linked polyethylene insulated material satisfies the safety requirement of high voltage direct current transmission and can be used for manufacturing long-distance transmission cables.

CORRELATION BETWEEN ELECTRICAL AND MECHANICAL CHARACTERISTICS OF CABLES WITH RADIATION-MODIFIED INSULATION ON THE BASIS OF A HALOGEN-FREE POLYMER COMPOSITION

Introduction. The high saturation of the cable routes of nuclear and thermal stations, wind parks and solar power plants, on-board systems imposes stringent requirements in the field of fire safety of cables, which makes it necessary to use highly flame retardant halogen-free compositions. The introduction of flame retardants causes the mandatory modification (crosslinking) of the polymer matrix. Purpose. Determination of the optimal radiation dose based on the correlation between the mechanical and electrical characteristics of a radiation-modified halogen-free ethylene vinyl acetate copolymer with high-strength flame retardant insulation cables. Methodology. Mechanical and electrical tests of samples of radiation-modified cables with a copper conductor cross section of 1.0 mm2 and a halogen-free filled insulation based on an EVA copolymer with a thickness of 0.7 mm have been performed. Results. A strong correlation is established between the elongation at break and the tensile strength, between the insulation resistance and the breakdown voltage. It is shown that at the optimum value of the irradiation coefficient in the range from 7 to 5, the insulation resistance increases more than twice, and the breakdown voltage at the direct current is increased by 1.3 times. The elongation at break is within the allowed values.

Partial Discharge Ultrasound Detection Using the Sagnac Interferometer System.

Partial discharge detection is crucial for electrical cable safety evaluation. The ultrasonic signals frequently generated in the partial discharge process contains important characteristic information. However, traditional ultrasonic transducers are easily subject to strong electromagnetic interference in environments with high voltages and strong magnetic fields. In order to overcome this problem, an optical fiber Sagnac interferometer system is proposed for partial discharge ultrasound detection. Optical fiber sensing and time-frequency analysis of the ultrasonic signals excited by the piezoelectric ultrasonic transducer is realized for the first time. The effective frequency band of the Sagnac interferometer system was up to 175 kHz with the help of a designed 10 kV partial discharge simulator device. Using the cumulative histogram method, the characteristic ultrasonic frequency band of the partial discharges was between 28.9 kHz and 57.6 kHz for this optical fiber partial discharge detection system. This new ultrasound sensor can be used as an ideal ultrasonic source for the intrinsically safe detection of partial discharges in an explosive environment.