Cable Condition Research Articles

Development of indentation techniques in support of cable condition monitoring programs

This paper summarizes work performed over the past few years at Atomic Energy of Canada Limited (AECL) to further develop indentation techniques in support of cable condition monitoring programs. Sensitivity to cable degradation of the commonly used specific compressive stiffness (or indenter modulus) is assessed based on laboratory testing of unaged, thermally aged, and irradiated cable samples. Another technique, which consists of measuring recovery time during the post-indentation phase, is also assessed for a variety of tested jacket and insulation materials. The document includes a review of the effect of indenter design and testing parameters on indentation results and provides input towards potential revisions of the IEC/IEEE 62582-2 Standard.

RTDS-based Model Component Development of a Tri-axial HTS Power Cable and Transient Characteristic Analysis

The transient characteristics of the tri-axial High Temperature Superconducting (HTS) power cable are different from those of a conventional power cable depending on whether the cable is under a steady or transient state due to the quench. Verification using simulation tools is required to confirm both the characteristics of the cable and the effect of the cable when it is applied to a real utility. However, a component for the cable has not been provided in simulation tools; thus the RTDSbased model component of the tri-axial HTS power cable was developed, and a simulation was performed under the transient state. The considered properties of model component include resistance, reactance and temperature. Simulation results indicate the variation of HTS power cable condition. The results are used for the transient characteristic analysis and stability verification of the tri-axial HTS power cable. In the future, the RTDS-based model component of the cable will be used to implement the hardware-in-the-loop simulation with a protection device.

Condition Monitoring of Medium Voltage Electrical Cables by Means of Partial Discharge Measurements

The purpose of this paper is to discuss condition monitoring (CM) of medium voltage electrical cables by means of partial discharge (PD) measurements. Electrical cables are exposed to a variety of operational and environmental stressors. The stressors will lead to the degradation of the cable's insulation material and ultimately to cable failure. The premature failure of cables can cause blackouts and will have a significant effect on the safety of such a network. It is therefore crucial to constantly monitor the condition of electrical cables. The first part of this paper is focussed on fundamental theory concepts regarding CM of electrical cables as well as PD. The derivation of mathematical models for the simulation of PD is also discussed. The simulation of discharge activity is due to a single void within the insulation material of medium voltage cross-linked polyethylene (XLPE) cables. The simulations were performed in the MATLAB ® Simulink ® environment, in order to investigate the effects of a variety of parameters on the characteristics of the PD signal. A non- intrusive CM technique was designed for the detection of PD activity within cables. The CM technique was used to measure and analyse practical PD data. Two MATLAB ® programs were

Correction Method of Cable Tension Measurement Bases on the Principle of Hamilton

In order to improve the accuracy of cable tension test, the motionequation of the stay cable with the rubber damper was established bases on the principleof Hamilton. First, the correction method for the damping coefficient of rubberdamper and cable tension was proposed according to the higher modal frequencyand measured frequency of cables difference. Then, take the cable of DongtingLake Bridge as an example, the cable tension was calculated by the proposedmethod and compared with the results of measurement by frequency method.Results showed that the proposed method can improve the accuracy of cabletension test and can effectively evaluate the cable tension condition of thecable-stayed bridge.

Finite Element Analysis of Guyed Offshore Monotower Subjected to Extreme Environment in Malaysian Water

This paper presents the finite element structural sensitivity analysis of a cable guyed monotower known as the Tarpon Monopod when subjected to extreme environments in Malaysian waters. A hydrodynamic loading and static platform response analysis is performed in SACS v5.3 to gauge the structural robustness in extreme Malaysian metocean conditions. A Stokes Fifth Order Wave Theory was employed to obtain wave kinematics and dynamics for load computation. The Tarpon Monopod design is reviewed generically. An actual platform located in 60m water depth within Malaysian waters is modelled for analysis. Four different guying cable scenarios are considered which are the fully guyed condition (three guy cables pinned), two guy cables condition (one wire loss), one guy cable condition (two wire loss) and free standing condition (total loss of guy wires) are presented. The environmental load sets are simulated at different headings using 45 degree steps. The results suggest that the structural caisson contributes little to the lateral stiffness of the platform. The Tarpon Monopod has little structural redundancy and its integrity is highly dependent on guy wire condition and environmental load headings.

Mechanical aging trend in ethylene propylene rubber-insulated safety cables sampled from bwr nuclear power containment

Statistical analysis has been performed on variously aged ethylene propylene rubber insulation on cables removed from boiling water reactor-type containment. Temperature and dose rate conditions of such cables are not identical. Therefore, elongation at break data observed for such insulation are converted to each equivalent period under 60 °C, 10 mGy/h condition. The aging trend is found to be approximately slower by half than that expected from accelerated aging test results. Furthermore, this aging trend is used as a reference to fit to each elongation value, and the fitted curve is extrapolated to find the end of service life, which is defined as 70 % of absolute elongation. Lifetimes estimated from this method and from predictions by the accelerated aging test are compared on an Arrhenius plot. It is suggested that the latter lifetime estimation is shorter than actual. The temperature dependence also suggests a difference in a basic chemical reaction under the two aging conditions, which results in apparent differences in activation energies and pre-exponential factors.

On-line PD detection and localization in cross-bonded HV cable systems

This paper addresses the detection and localization of partial discharge (PD) in crossbonded (CB) high voltage (HV) cables. A great deal has been published in recent years on PD based cable insulation condition monitoring, diagnostics and localization in medium voltage (MV) and high voltage (HV) cables. The topic of pulse propagation and PD source localization in CB HV cable systems has yet to be significantly investigated. The main challenge to PD monitoring of CB HV cables is as a result of the interconnectedness of the sheaths of the three single phase cables. The cross-bonding of the sheaths makes it difficult to localize which of the three phases a PD signal has emanated from. Co-axial cables are used to connect cable sheaths to cable link boxes, for ease of installation and protection against moisture. A second challenge is, therefore, the coupling effect when a PD pulse propagates in HV cable joints and the co-axial cables, making PD detection and localization more complex. The paper presents experimental investigations into PD pulse coupling between the cable center conductor and the sheath and the behavior of PD pulse propagation in CB HV cables. It proposes a model to describe PD pulse propagation in a CB HV cable system to allow monitoring and localization, and also presents the knowledge rules required for PD localization in CB HV cable systems.

Remote monitoring of partial discharge data from insulated power cables

Partial discharge (PD) diagnostics is one of the most widely used tool to assess the insulation condition of insulated power cables and which facilitates informed maintenance planning leading to the extension of the service life of such ageing assets. PD occurs with varying intensity due to circuit loading and weather conditions. Proven systems based on off-line PD diagnostics find limited application, since this method requires a circuit outage. In this study, remote controlled PC based PD monitoring system using client server technology is proposed. Continuous monitoring of cable network using the proposed system can capture sudden or gradual changes in PD activity which is often difficult in conventional PD monitoring systems which are based on spot measurement. In this system, the remote control capability using internet has been implemented to reduce the frequency of site visits which in turn reduces the cost of manpower. Relational database management system is used as a back-end server for data storage, data analysis and data management. This would help the utility to maintain insulation integrity history database which can be used for cable renewal program in the longer term. System design, testing, implementation and field measurements are discussed.

Probabilistic deterioration model of high-strength steel wires and its application to bridge cables

Bridge inspections reveal that severe corrosion and fatigue are the main failure mechanisms of bridge stay cables. This paper presents an empirical modelling of the long-term deterioration process of steel wires in cables with consideration of the simultaneous occurrence of uniform corrosion, pitting corrosion and fatigue induced by a combined action of environmental aggression and cyclic loading. Accelerated corrosion experiments are conducted to determine the different corrosion levels of high-strength steel wires, and time-dependent statistical models are developed to quantify uniform and pitting corrosion depth. Corrosion-fatigue process of steel wires is subsequently simulated using the corrosion models and cyclic stress obtained through cable force monitoring data. The mechanical properties of corroded steel wires, including yield stress, ultimate stress, ultimate strain and modulus of elasticity, are experimentally characterised, and the statistical models are established through regression analysis. Finally, the deterioration models of high-strength steel wires (including crack depth, ratio of broken wires, and remaining strength, among others) is extended to probabilistically assess the time-variant conditions of bridge cables (sectional area loss and remaining capacity). The presented study on the long-term deterioration of bridge cables would provide guidance to future decision-making regarding the maintenance and replacement of bridge cables.

Parameter estimation technique for the semi-conducting layers in single-core XLPE cable

Partial discharge (PD) detection and location is of great significance for the power cable insulation condition monitoring, where the high-frequency (HF) model is needed to analyze PD propagation. Considering the influences of conductor skin effects and semi-conducting layers (SCL), this paper presents the equivalent Γ-section lumped parameter model for single-core cross-linked polyethylene (XLPE) insulation cables. The longitudinal parameters per-unit-length in the model are obtained using available geometric data by vector fitting method. Unfortunately, the dielectric characteristics of SCL in XLPE cables, especially for an installed one, are usually unknown and hard to measure. To address this issue, based on the simulated annealing algorithm, an optimization approach for estimating the transversal parameters in the Γ-circuit model is developed. The proposed technique is then carried out on the XLPE cable with simulated and real SCL, respectively. Furthermore, the estimation results of the real case are validated on a 603 m cable with kinds of HF pulses responses.

Power Transfer Capability of HVAC Cables for Subsea Transmission and Distribution Systems

This paper provides a methodology to estimate power versus distance envelops of High-Voltage Alternating Current (HVAC) transmission system for subsea applications. AC technology is mature and proven for land-based applications and relatively short off-shore tiebacks. However, for long tiebacks, due to increased conductor capacitance, large reactive power needs to be supplied, leading to higher cable current rating, losses, and expensive umbilical. Subsea AC cables are limited in their capability to transmit power beyond a certain distance, depending on cable characteristics, installation conditions and system operating mode. Power transfer boundary charts for AC technology based on analytical methods are presented. Analytical calculations and computer simulations of HVAC power cables were performed on more than 30 cables with rated voltage between 35 and 150 kV and cable cross-sections between 95 and 400 mm2. Effects of reactive compensation on system tieback distance have been analyzed, as well as low frequency transmission and different modes of system operation. Cable models employing multiple pi-sections and distributed parameters were used. Well-known power flow and simulation tools were used for validation. AC transmission boundaries were estimated based on the voltage and current limits for various cables under various operating modes.

Bridge Pavla Wonky in Pardubice. Diagnostics of Corrosion Condition of External Cables and Use of Special Materials for Proposal of Treatment

Annotation: Complete reconstruction of the reinforced prestressed bridge Pavla Wonky in Pardubice was carried out in 2006. During this reconstruction specialists of the Klokner's Institute made complete revision of linear free external cables in bridge chambers, namely from the aspect of corrosion. Some of the findings obtained during this revision are presented in this article.

Simulation of Partial Discharge Propagation Characteristics in XLPE Cables and Joints

Accurate Partial discharge (PD) detection and location is of great significance for the power cable insulation condition monitoring. To achieve this, an adequate cable model to analyze pulse propagation is needed. Considering the complex structure of the cable, the equivalent circuit model is no longer applicable. In this paper a numerical electromagnetic method, FDTD, is applied. To analysis wave propagation characteristics in time domain, a well-established cable model is constructed. By simulating the electromagnetic (EM) field propagation inside the cable and the cable joint, the components of the electric fields excited by the PD source in different directions are calculated in order to evaluate the influence of the cable joint in practice, the calculated PD waveforms in the cable are compared with those of the cable joint model in FDTD.

Magnetic Flux Leakage Sensing-Based Steel Cable NDE Technique

Nondestructive evaluation (NDE) of steel cables in long span bridges is necessary to prevent structural failure. Thus, an automated cable monitoring system is proposed that uses a suitable NDE technique and a cable-climbing robot. A magnetic flux leakage- (MFL-) based inspection system was applied to monitor the condition of cables. This inspection system measures magnetic flux to detect the local faults (LF) of steel cable. To verify the feasibility of the proposed damage detection technique, an 8-channel MFL sensor head prototype was designed and fabricated. A steel cable bunch specimen with several types of damage was fabricated and scanned by the MFL sensor head to measure the magnetic flux density of the specimen. To interpret the condition of the steel cable, magnetic flux signals were used to determine the locations of the flaws and the levels of damage. Measured signals from the damaged specimen were compared with thresholds that were set for objective decision-making. In addition, the measured magnetic flux signals were visualized as a 3D MFL map for intuitive cable monitoring. Finally, the results were compared with information on actual inflicted damages, to confirm the accuracy and effectiveness of the proposed cable monitoring method.

Characterization of Mechanical Properties of MgB2 conductor for Superconducting Link Project at CERN

In the framework of high luminosity upgrade of Large Hadron Collider at CERN, superconducting links are being developed. MgB2 wire is a candidate conductor for use in high- current cables. Mechanical properties of this material are of key importance for the definition of the cable design and operating conditions. In this study, we evaluated the Young’s modulus of MgB2 filaments extracted from ex situ processed composite wires. The wires were produced in unit lengths of about 1 km and used in high-current cables. Single fiber tensile test was carried out on fil- aments composed of MgB2, Nb barrier, and Nb–Ni reaction layer. From the unloading modulus of filament specimens measured with different gauge lengths, the Young’s modulus of composite filaments extracted from two different strands was determined to be 114 and 122 GPa at room temperature, respectively. By using the rule-of-mixture, the Young’s modulus of MgB2 was estimated to be lower than that reported for highly dense MgB2 bulks. The reason for such difference is discussed from the viewpoint of void fraction.

Transmission Characteristic Analysis of PD Signal in Power Cable

Partial discharge is one of the most common fault of power cable. It is of great significance to detect and analyze the condition of the power cable and locate the fault of the power cable. The model of partial discharge signal is constructed by a double exponential function. The simulation model of power cable with a middle fault is built by MATLAB SIMULINK. The transmission characteristic of partial discharge in different length of power cable and different types of power cable is simulated respectively. The simulation results show that the attenuation is proportional to the length of the same type of cable and the primary parameter of different type of power cables determines the attenuation.

Partial discharge location in power cables using a double ended method based on time triggering with GPS

Partial discharge (PD) diagnostics is the most widely used tool to assess the insulation condition of insulated power cables which facilitates informed maintenance planning leading to extended service life of ageing assets. Time domain reflectometry (TDR) using a single ended or double ended approach is the most widely used method for locating PD sources. The success of the single ended method is dependent upon cable network design. However, by monitoring PDs at both ends of the cable, i.e. double-ended PD monitoring, higher accuracy of PD location can be achieved with a higher success rate. The double ended method is not widely used due to its complex system design, time synchronization and communication requirement between measurement units. This paper proposes a double ended PD location system which triggers on the predefined one pulse per second (1PPS) signal obtained from a global positioning systems (GPS) using novel time based triggering logic (TBTL) implemented in field programmable gate arrays (FPGA). This system ignores non-useable (not synchronized) data caused by flywheel 1PPS from GPS receiver due to any short-term loss of satellite signals which eventually reduces the PD location accuracy. Furthermore TBTL also ignores spurious triggering pulses radiated from noise sources within the substation. With the use of a communication link between two ends of the cable provided via mobile broadband together with TBTL, eliminated the acquisition of non-useable(not synchronized) data. Based on laboratory tests and on-site measurements PD location accuracy of less than ± 10 m can be achieved. The system design, laboratory tests and on-site measurements are discussed.

The Design and Implementation of Cable Condition Monitoring System

This paper describes the detail of design and implementation of cable condition monitoring system, including accessing and sharing of monitoring data, visualization, query, analysis and device management.

The Life Cycle Reliability Evaluation of Optical Cable

Along with the optical fiber communication technology is widely used in power system, optical cable fault which will lead to failure has become an important factor influencing power grid reliability, but the existing optical cable evaluation index is single, only statistical cable fault conditions operation index, can not fully reflect the actual reliability of cable. This paper tries to construct a whole life cycle based on optical cable statistical reliability evaluation index system, uses the entropy method to evaluate the reliability of the optical cable is more objective, true, to carry out cable reliability research has certain reference significance. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2379

Determining the grounding length of an axially moving cable in a two-ship continuous line bucket system

This study investigates the two-dimensional static mechanics of an axially moving cable used in a two-ship continuous line bucket (CLB) system for exploiting mineral resources deposited on the sea floor. The aim of this study is to formulate a theory for estimating the grounding length of the cable. The theory is governed by the relation for the static equilibrium of forces acting on the cable and geometrical conditions imposed on the submerged length of the cable and on the distance between the two ships supporting the cable. Two algorithms involving a couple of iterations are developed for obtaining the grounding length. The calculation using the algorithm shows that the grounding length varies in response to changes in the rate of collection by the bucket and the bucket interval. The calculation also demonstrates that the maximum grounding length is determined on the basis of the geometry of the submerged part and that the grounding length ranges from zero to the maximum depending on the distance between the two ships.