Cable Monitoring Research Articles

Modelling and experimental validation of EM wave propagation due to PDs in XLPE cables

Monitoring of electromagnetic (EM) waves due to partial discharge (PD) is a promising tool for condition monitoring of cables. This study presents the development of a modelling scheme for simulation of EM wave propagation due to PDs occurring at cavities in the cross-linked polyethylene (XLPE) insulation. Simulation models for generation and propagation of PD pulses through the cable geometry are developed. A finite element method (FEM)-based model is developed to simulate the PD current along cylindrical voids in the cable insulation. The initial fields due to the PD currents in the voids are simulated by an FEM model. The propagated EM fields inside and outside the cable surface due to PD's occurring inside the voids are analysed by a finite-difference time-domain model. The analysis of propagated EM fields due to a Gaussian-shaped PD pulse identifies the dominant components of propagated electric and magnetic fields along the cable geometry. Furthermore, the propagated EM fields at the cable sheath due to different void dimensions are simulated and experimental validation of the propagated magnetic field is conducted with measurement by an high-frequency current transformer sensor installed around an earth wire from the sheath of an 11 kV XLPE cable.

Performance Enhancement Methods for the Distributed Acoustic Sensors Based on Frequency Division Multiplexing

The last years have witnessed the wide application of Distributed Acoustic Sensor (DAS) systems in several fields, such as submarine cable monitoring, seismic wave detection, structural health monitoring, etc. Due to their distributed measurement ability and high sensitivity, DAS systems can be employed as a promising tool for the phase sensitive optical time domain reflectometry (Φ-OTDR). However, it is also well-known that the traditional Φ-OTDR system suffers from Rayleigh backscattering (RBS) fading effects, which induce dead zones in the measurement results. Worse still, in practice it is difficult to achieve the optimum matching between spatial resolution (SR) and signal to noise ratio (SNR). Further, the overall frequency response range (FRR) of the traditional Φ-OTDR is commonly limited by the length of the fiber in order to prevent RBS signals from overlapping with each other. Additionally, it is usually difficult to reconstruct high frequency vibration signals accurately for long range monitoring. Aiming at solving these problems, we introduce frequency division multiplexing (FDM) that makes it easier to improve the system performance with less system structure changes. We propose several novel Φ-OTDR schemes based on Frequency Division Multiplexing (FDM) technology to solve the above problems. Experimental results showed that the distortion induced by fading effects could be suppressed to 1.26%; when the SR of Φ-OTDR is consistent with the length of the vibration region, the SNR of the sensing system is improved by 3 dB compared to the average SNR with different SRs; vibration frequencies up to 440 kHz have been detected along 330 m artificial microstructures. Thus, the proposed sensing system offers a promising solution for the performance enhancement of DAS systems that could achieve high SNR, broadband FRR and dead zone-free measurements at the same time.

A data mining method based on unsupervised learning and spatiotemporal analysis for sheath current monitoring

Sheath current is one of the key indicators of underground power cable conditions. Considering the limitations of existing model-based methods for sheath current monitoring and difficulty in handling the increasing amount of unlabeled sheath current data accumulated by cable monitoring systems, we propose a data mining method based on unsupervised learning and spatiotemporal analysis of sheath currents for underground power cable monitoring. Tests based on real historical data demonstrate that the proposed method can effectively reveal unknown inherent patterns in unlabeled sheath current data.

A Guided Wave Transducer with Sprayed Magnetostrictive Powder Coating for Monitoring of Aluminum Conductor Steel-Reinforced Cables.

Aluminum conductor steel-reinforced (ACSR) cables are typically used in overhead transmission lines, requiring stringent non-destructive testing owing to the severe conditions they face. Ultrasonic guided wave inspection provides promising online monitoring of the wire breakage of cables with the advantages of high sensitivity, long-range inspection, and full cross-sectional coverage. It is a very popular method to generate and receive guided waves using magnetostrictive and piezoelectric transducers. However, uniformly coupling the acoustic energy excited by transducers into multi-wire structures is always a challenge in the field application of guided waves. Long-term field application of piezoelectric transducers is limited due to the small coupling surface area, localized excitation, and couplant required. Conventional magnetostrictive transducers for steel strand inspection are based on the magnetostrictive effect of the material itself. Two factors affect the transducing performance of the transducers on ACSR cables. On one hand, there is a non-magnetostrictive effect in aluminum wires. On the other hand, the magnetostriction of the innermost steel wires is too weak to generate guided waves. The bias magnetic field is attenuated by the outer layers of aluminum wires. In this paper, an alternative sprayed magnetostrictive powder coating (SMPC) transducer was developed for guided wave generation and detection in ACSR cables. The Fe83Ga17 alloy powder with large magnetostriction was sprayed uniformly on the surfaces of certain sections of the outermost aluminum wires where the transducer would be installed. Experimental investigations were carried out to generate and receive the most commonly used L(0,1) guided waves for wire breakage detection at frequencies of 50 and 100 kHz. The results demonstrate that the discernable reflected waves of the cable end and an artificial defect of three-wire breakage (5.5% reduction in the cable’s cross-sectional area) were received by the transducer with SMPC, which was impossible for the transducer without SMPC. This method makes long-term and online monitoring of ACSR cables feasible due to the high coupling efficiency and good structural surface adaptability.

Numerical and Experimental Investigation of Guided Wave Propagation in a Multi-Wire Cable

Ultrasonic guided waves (UGWs) have attracted attention in the nondestructive testing and structural health monitoring (SHM) of multi-wire cables. They offer such advantages as a single measurement, wide coverage of the acoustic field, and long-range propagation ability. However, the mechanical coupling of multi-wire structures complicates the propagation behaviors of guided waves and signal interpretation. In this paper, UGW propagation in these waveguides is investigated theoretically, numerically, and experimentally from the perspective of dispersion and wave structure, contact acoustic nonlinearity (CAN), and wave energy transfer. Although the performance of all possible propagating wave modes in a multi-wire cable at different frequencies could be obtained by dispersion analysis, it is ineffective to analyze the frequency behaviors of the wave signals of a certain mode, which could be analyzed using the CAN effect. The CAN phenomenon of two mechanically coupled wires in contact was observed, which was demonstrated by numerical guided wave simulation and experiments. Additionally, the measured guided wave energy of wires located in different layers of an aluminum conductor steel-reinforced cable accords with the theoretical prediction. The model of wave energy distribution in different layers of a cable also could be used to optimize the excitation power of transducers and determine the effective monitoring range of SHM.

Numerical modelling, simulation and experimental validation of partial discharge in cross‐linked polyethylene cables

A clear understanding of the partial discharge (PD) phenomena occurring in cavities at various radial locations in the insulation is essential for proper monitoring of cables. This work presents a comparison of finite element method (FEM) model and capacitive model for simulation of PD in the insulation and an attempt to identify reliable parameters for monitoring the condition of cable insulation is done. A three-dimensional FEM-based model of the cable is developed in ANSYS software by including the effects of surface charge accumulation and propagation along with the phenomena of charge decay at the void surface. The induced charge concept which is correlated with changes in capacitance is employed to model a capacitive model for simulation of PD by considering the free electron availability for simulation of PDs in cables in EMTP software. The experimental validation of developed models is done by PD measurement on 11 kV cross-linked polyethylene cables. Analysis of the simulation results recommends the relevance of the capacitive model to be employed for condition assessment of cable insulation in view of its simplicity and appropriateness in the estimation of model parameters from actual cable measurements.

Processing and analysis of power cable monitoring data based on big data

Processing and analysis of power cable monitoring data based on big data

Simulation Research on On-line Multi-parameter Monitoring for Long Distance Three-phase Power Cable

Long distance three-phase power cable has the characteristics of the metal sheath cross-bonded and voltage drop and ground potential difference at both ends, which brings confusion to on-line insulation monitoring of long distance power cable. One parameter monitoring cable insulation will effect by voltage drop, load current change, frequency fluctuation and other factor. A method based on dielectric loss factor and resistive current to monitor cable insulation simultaneously has been put forward. The method named as a multi-parameter on-line cable insulation monitoring method. The method installs current transformers and voltage transformers on both side of three-phase cable and uses a high precision timing function of the GPS receiving module at both ends of the testing equipment respectively which can receives the pulse per second from the GPS satellite as time reference can realize the signal synchronous sampling. The principle and formula of the method are given. The metal sheath cross-bonded equivalent circuit of long distance three-phase cable is established by using MATLAB software and does dynamic simulation on the method. The results show that the method is not effect on load current, voltage drop and frequency fluctuation. The two parameters increase obviously when the cable operating temperature exceeds 80°C. The insulation condition of three-phase cable can be judged by the change of dielectric loss factor and resistive current under different insulation fault. The method was proved to be correctness and feasibility in the paper.

Online Partial Discharge Insulation Condition Monitoring of Complete High-Voltage Networks

Renforth et al. in 2017 present a novel online partial discharge (OLPD) high-voltage (HV) insulation condition monitoring (CM) solution to monitor complete HV networks in petrochemical and other critical industry facilities. Continuous, 24/7 OLPD insulation monitoring of in-service cables, switchgear, transformers, and rotating machines operating at 3000 V and above provides operators with an early warning against incipient HV insulation faults that manifest themselves through high PD activity. Knowledge of the type, severity, and source of any site(s) of PD across the HV network (including remotely connected plant such as Ex/ATEX HV motors located in hazardous gas zones) enables pinpointed preventative maintenance interventions to be made to the HV insulation system during planned maintenance turnarounds to avoid unplanned outages. To monitor a complete HV network, OLPD sensors and monitoring nodes are distributed at strategic locations across the network. The CM data from the distributed nodes are passed via Ethernet/LAN to a partial discharge monitoring server (PDMS) located at the control center of the facility with a secure internet connection. The PDMS operates an advanced OLPD monitoring database for the logging, display, benchmarking, trending, and visualization of the PD monitoring data on a graphical user interface. The insulation condition criticality (from 0% to 100%) of each phase of all of the individual HV plant items monitored is presented on a series of mimic screens of the HV network single-line diagram. This paper concludes with a case study of a complete HV network OLPD monitoring design solution implemented at a large, crude-oil processing facility in Eurasia.

Identification and Location of PD Defects in Medium voltage Underground Power Cables Using High Frequency Current Transformer

Fault location is an important diagnostic task in condition monitoring of underground medium voltage cables. Available solutions are well capable of determining the location of a single partial discharge (PD) defect on a cable section. In case several PD defects are active simultaneously along a cable section, the interpretation of the measured data becomes complex to identify the presence of more than one PD sources. In this paper, experimental investigation of two PD defects/sources at different locations on a medium voltage (MV) cable section is presented. A high frequency current transformer is used for single end PD measurements. Time domain reflectometry-based in-depth study of the reflected pulses provides the most valuable information to identify the presence of PD sources which further leads to the location of the individual PD sources. In this paper, the proposed solution is presented for two PD sources, however, the same methodology can be extended to locate multiple PD sources on the cable.

半径确定的最小二乘圆拟合法在电缆卷绕监测中的应用

半径确定的最小二乘圆拟合法在电缆卷绕监测中的应用

Design of 1-μm-band mode-detection OTDR for 40 km range measurement and its performance evaluation

Abstract This paper clarifies the requirements for applying 1-μm-band mode-detection optical time domain reflectometry (OTDR) to the loss monitoring of trunk cables with the goal of detecting slight changes in macro/micro-bending that are missed by conventional OTDR. In light of the requirements, the measurement system is enhanced through the use of coherent detection to fulfill the required range performance. Moreover, the enhanced system modulates the optical frequency and the state of polarization of the probe light during the measurement to suppress amplitude fluctuations in the backscattered waveforms. A field test is carried out to confirm the performance of the enhanced measurement system. The results demonstrate that the measurement range of over 40 km is achieved while amplitude fluctuations are reduced to as low as 0.02 dB.

Temperature Compensation of Elasto-Magneto-Electric (EME) Sensors in Cable Force Monitoring Using BP Neural Network.

Techniques based on the elasto-magnetic (EM) effect have been receiving increasing attention for their significant advantages in cable stress/force monitoring of in-service structures. Variations in ambient temperature affect the magnetic behaviors of steel components, causing errors in the sensor and measurement system results. Therefore, temperature compensation is essential. In this paper, the effect of temperature on the force monitoring of steel cables using smart elasto-magneto-electric (EME) sensors was investigated experimentally. A back propagation (BP) neural network method is proposed to obtain a direct readout of the applied force in the engineering environment, involving less computational complexity. On the basis of the data measured in the experiment, an improved BP neural network model was established. The test result shows that, over a temperature range of approximately −10 °C to 60 °C, the maximum relative error in the force measurement is within ±0.9%. A polynomial fitting method was also implemented for comparison. It is concluded that the method based on a BP neural network can be more reliable, effective and robust, and can be extended to temperature compensation of other similar sensors.

A Laser-Based Noncontact Vibration Technique for Health Monitoring of Structural Cables: Background, Success, and New Developments

Structural cables are susceptible to the effects of high stress concentrations, corrosion, and wind-induced and other vibrations. Cables are normally the most critical elements in a cable-supported structure and their well-being is very important in the health of the structure. The laser-based vibration technique discussed in this paper is a means for health monitoring of cables and therefore the entire cable-supported structure. This technique uses a noncontact remote sensing laser vibrometer for collecting cable vibration data from distances of up to several hundreds of feet and determines its dynamic characteristics including vibration frequencies and damping ratios. A formulation specifically developed for structural cables capable of accounting for important cable parameters is then used to calculate the cable force. Estimated forces in the cables are compared to previously measured forces or designer’s prediction to detect patterns associated with damage to the cable itself and/or changes to the structure elsewhere. The estimated damping ratios are also compared against predefined criteria to infer about susceptibility against wind-induced vibrations and other vibrations. The technique provides rapid, effective, and accurate means for health monitoring of cable-supported structures. It determines the locations and elements with potential damage and the need for detailed and hands on inspection. To date, the technique has been used successfully for evaluation of twenty-five major bridges in the US and abroad. Though originally devised for condition assessment of stay cables, it has been developed further to include a variety of systems and conditions among them structural hanger ropes in suspension, truss, and arch supported bridges, ungrouted stay cables, cables with cross-ties, and external posttensioning tendons in segmental bridge construction. It has also found a valuable place in construction-phase activities for verification of forces in tension elements with minimal efforts. Future endeavors for automation and aerial delivery are being considered for this technique.

Numerical study of influential factors on partial discharges in HVDC XLPE cables

PurposeFor the dramatically developed high voltage direct current (HVDC) power transmission, HVDC cables play a vital role in the power transmission across seas and connections with renewable power sources. However, the condition monitoring of HVDC cables is still a challenging research topic. This paper aims to understand the influence of external factors, namely, current, cavity location and material properties, on partial discharge (PD) characteristics in HVDC cable in a numerical way referring to the refined Niemeyer’s model.Design/methodology/approachThe influences of the three external factors are studied by a proposed numerical model for DC PDs based on the modification of a conventional PD model for AC voltage via a finite element analysis method.FindingsThe external factors can influence the discharge magnitude and discharge repetition rate via affecting the electrical conductivity of the material: DC PD is more frequent and with higher discharge magnitude when the cavity is closer to the conductor or the current through the conductor is higher. Both DC PD repetition rate and average discharge magnitude in long-term aged material are lower than virgin material. The effect of discharge on insulation degradation becomes decreasingly significant.Research limitations/implicationsThe current work is based on the numerical modelling of DC PDs. Further experimental validations and comparisons are essential for improving the model.Practical implicationsThe studies of the influence factors for PDs under HVDC voltage can benefit the research and practical power transmission on DC PDs, contributing the design and test of DC PDs in HVDC cables, exploring the understandings of the DC PDs’ mechanism.Originality/valueThis paper, to the best of author’s knowledge, first studies the influence factors on DC PDs based on the numerical modelling work.

On-line monitoring system of 35 kV 3-core submarine power cable based on φ-OTDR

Submarine power cables are important in power transmission for islands, sea platform and wind plant. They are lying under the sea and endure the threatening of anchor while there is no effective method to find the anchor damage in time. In order to solve the problem, the anchor damage detection of submarine power cable based on φ-OTDR is proposed. The frequency measurement range of φ-OTDR has been tested as 0–800 Hz which can satisfy the requirement of optical fiber vibration sensing in submarine power cable. An optical fiber vibration monitor system is realized and put into service in a 35 kV three-core submarine power cable laid between two islands in China. The anchor drop and anchor drag incidents have been simulated. The vibration data of calm sea, anchor drop and anchor drag have been obtained and analyzed. Analysis results indicate that there are differences between calm sea, anchor drop and anchor drag in energy and amplitude distribution, the faults can be identified according to the differences. The anchor damage detection method proposed in this paper provides a feasible scheme for the on-line monitoring of the submarine power cable, which can early warn and alarm the anchor damage to submarine power cables.

Robust Condition Assessment of Electrical Equipment with One Class Support Vector Machines Based on the Measurement of Partial Discharges

This paper presents a system for the detection of partial discharges (PD) in industrial applications based on One Class Support Vector Machines (OCSVM). The study stresses the detection of Partial Discharges (PD) as they represent a major source of information related to degradation in the equipment. PD measurement is a widely extended technique for condition monitoring of electrical machines and power cables to avoid catastrophic failures and the consequent blackouts. One of the most important keystones in the interpretation of partial discharges is their separation from other signals considered as not-PD especially in low SNR measurements. In this sense, the OCSVM is an interesting alternative to binary SVMs since it does not need a training set with examples of all the output classes correctly labelled. On the contrary, the OCSVM learns a model of the signals acquired when the equipment is in PD-free mode, defined as a state where no degradation mechanism is active, so one only needs to make sure that the training signals were recorded under this setting. These default mode signals are easier to characterize and acquire in industrial environments than PD and lead to more robust detectors that practically do not need domain adaptation to perform in scenarios prone to different types of PD. In fact, the experimental results show that the performance of the OCSVM is comparable to that achieved by a binary SVM trained using both noise and PD pulses. Finally, the method is successfully applied to a more realistic scenario involving the detection of PD in a damaged distribution power cable.

Application of intelligent anchor cable axial force monitoring system in foundation pit support engineering

Using the self-developed intelligent anchor (cable) axial force monitoring system, real-time on-line monitoring of the axial force of the prestressed anchor and anchor cable in the foundation pit support structure system is realized. The system has automatic acquisition, wireless transmission, real-time monitoring and other advantages. Through actual engineering application and comparative analysis of traditional methods of monitoring data, it can be seen that the monitoring data is also valid and reliable, and the continuity and difference error of the measured curve is better than the traditional method. The system monitoring data can better reflect the relationship between the support structure stress, deformation and construction process in the foundation pit engineering and provide a strong guarantee for the safe and efficient construction of the foundation pit project.

Application of Acoustic Emission Technique for Bridge Cable Monitoring

Application of Acoustic Emission Technique for Bridge Cable Monitoring

Review of Machine Vision Based Insulator Inspection Systems for Overhead Power Distribution System

The necessity to have reliable and quality power distribution is increasing, and hence there is great scope for research on automation of distribution system. There are signs of increased research in the work on condition monitoring of insulators during the last few decades. The possible failures can be predicted before they actually occur by using the condition monitoring of cables or any electrical equipment on-line. Those assets such as towers, conductors and insulators which are on the threshold of failure have to be replaced or repaired, so that forced outages reduce. Traditionally the workers who inspect these lines check them in close proximity by going for foot-patrolling and pole-climbing. With an incredible expansion of power distribution network even to remote areas, previously mentioned methods do not seem to be viable. In developed countries aerial patrolling has been adopted to monitor the insulators as an alternative. The development of an efficient method of condition monitoring by using image processing followed by machine learning techniques is found to be a suitable method and thus emerging as a feasible option for real-time implementation. This review paper covers overall aspects of automatic detection of defects of insulator systems of electric power lines and classification into different classes by using vision-based techniques.