Broken Conductor Research Articles

Dynamic Response of Iced Overhead Electric Transmission Lines Following Cable Rupture Shock and Induced Ice Shedding

Improved ice detachment failure criteria were implemented into the finite-element dynamic analysis of iced power transmission lines subjected to cable rupture shocks, which allows the study of the ice shedding effects that have been induced by the initial shocks. The modeling method is validated first experimentally by full-scale physical tests and then numerically by comparing with previous numerical methods. The case study shows that after considering the ice detachment failure subsequent to the initial rupture shock, the dynamic response of the iced line is significantly different from that obtained with previous iced line models that ignore the induced ice shedding effects. It shows that the previous equivalent density method tends to overestimate and the previous strain method tends to underestimate the maximum values and dynamic impact factors of cable tensions and insulator forces for the iced line following conductor breakage. It also shows that the cable-ground contact effect plays quite a different role in the bare cable model and iced line models. The proposed method can help improve the structure design of transmission lines and can also be used to study the dynamic response of lines subjected to other modes of line components failure, such as clamp slippage, insulator rupture, and tower deformation.

Comparison of Responses of Guyed and Freestanding Transmission Line Towers Under Conductor Breakage Loading

Cascades have been a prominent feature of many transmission line (TL) accidents around the world. During these events, a localized member failure changes the boundary conditions of the structural system, magnifying member loads over a considerable extension of the line. This results in the progressive failure of successive support structures. Phase conductor breakage is regarded as the most severe cascade triggering event, generating a shock wave that propagates through the conductor and induces large unbalanced longitudinal loads on the transmission line components. Under such an extreme loading event, nonlinear time-history dynamic analysis has to be employed to predict the response of the TL system. In the present work, an explicit dynamic analysis scheme is developed to predict the response of a multi-span TL section. The analysis includes all the main structural components of a TL section. This procedure was used to investigate the response of two types of suspension steel latticed towers, guyed and freestanding, subjected to conductor breakage loading. Results indicate the occurrence of peak dynamic loads (PDLs), that significantly increase the internal forces in system components, exceeding their design capacities, particularly in tower's members. The results also show that the guyed tower accommodates such a loading event more adequately than the freestanding tower.

Challenges in Detection of High Impedance Faults on Broken Conductors in MV Lines

The weather conditions in Saudi Arabia are harsh and the inland areas are very hot, dry and sandy. Thousands of kilometers of medium voltage overhead lines (13.8 kV) are located in deep desert areas feeding loads that are located in remote desert areas. Such medium and low voltage distribution networks face difficulties regarding fault detection and localization. High Impedance Fault (HIF) resulting from a broken conductor in MV overhead lines represent the most challenging problem in such environments. Such condition may cause damage, fire or electric shock hazards resulting in life threatening situations. This study reports on a study of electrical characteristics of inland desert sand and typical characteristics of HIF fault when a MV line conductor breaks and touches such sand. It is shown that the arid desert sand has extremely high resistivity and it is difficult to detect the fault by using conventional protective devices. The study presents results of measurements and simulations and suggests that innovative approaches have to be employed to achieve the desired protection in such environments.

Simulation and Experiential Research for Broken Conductor Load of Suspension Towers of UHVDC Power Transmission

The breakage of conductor/ground wire seriously affects the secure operation of transmission line. According to the features of UHVDC power transmission lines, the broken conductor model for bundled conductors of continuous span is built and the broken conductor load is calculated; A simulating test was carried out the first time in China for a series of "broken conductor" events on one continuous span on the field to study the dynamic response of the transmission tower because of impact, then the dynamic strain and displacement were obtained. On the basis of the simulation and experiential research results, the paper discussed about the rational values of broken wire loads for the suspension towers of UHVDC.

Directional ground relay failure caused by line‐to‐ground with load‐side broken conductor fault

SUMMARYClassic power system fault analysis considers canonic situations, such as three‐phase, line‐to‐line, double line‐to‐ground and line‐to‐ground faults. However, in practice, other faults occur that may be undetected by the protection systems. For example, a fault happens when a line conductor breaks and falls to the ground at the load side in a radial distribution network. This particular fault is called the “line‐to‐ground with broken conductor fault”. The aim of this work is a deep analysis of this particular contingency. In the first part, the proposed theory based on symmetrical components transformation is presented. Subsequently, the study of a MV radial distribution test network is considered in order to show the protection trip failure conditions. Copyright © 2011 John Wiley & Sons, Ltd.

SVM‐based method for high‐impedance faults detection in distribution networks

PurposeThe purpose of this paper is to present a new pattern recognition‐based algorithm to detect high‐impedance faults (HIFs), including only with broken conductor and arcs, in distribution networks.Design/methodology/approachIn the proposed method, using discrete wavelet transform, the time‐frequency‐based features of the current waveform are calculated. Then, to extract the best feature set of the generated time‐frequency features, principle components analysis (PCA) is applied and finally support vector machines (SVM) is used as a classifier to distinguish between the HIFs, including only with broken conductor and arcs, and other similar phenomena such as capacitor banks switching, no load transformer switching, load switching, insulator leakage current and harmonic loads.FindingsThe experimental results have shown that using SVM with PCA as the feature extraction method and radial basis function (RBF) as the kernel function has acceptable security and dependability performances in distinguishing HIFs, including only with broken conductor and arcs, from other similar phenomena and is superior to the Bayes and multi‐layer perceptron neural network classifiers.Originality/valueUsing new combination of time‐frequency‐based features with SVM provides a new algorithm to detect HIFs, including only with broken conductor and arcs, that has acceptable security and dependability.

Analysis on the Dynamic Responses of the Broken Conductors in Transmission Lines

Impact loads from the broken conductors are common for transmission lines, which can bring threaten to the safe operation of the transmission lines. Dynamic analysis of the conductors in transmission lines under broken load was carried out. A finite element model of seven span conductors in transmission line was established in general software ANSYS. The insulator and the phase spacer were considered in the FEA model. The broken load case can be realized by the birth-death element method in ANSYS. Stiffness of the broken conductor or insulator element was changed to be a near zero value in a very short time. Effect of the damping property of the conductors was considered by the Rayleigh damping method. Dynamic responses of displacements at the broken points and the reaction forces of the insulators were obtained. Dynamic responses for the broken conductors with different damping ratios and bundle numbers were compared.

Dynamic Response of Conductor Breakage for Oxytropis Transmission Tower-Line System

Dynamic response of conductor breakage is analyzed on guyed oxytropis transmission tower-line system of 500KV 5291 JinJiang-Zhenjiang lines. Considering unbalanced tension, finite element method is presented. Result of the transient analysis shows that the vibration of tower-line system happens after conductor breakage. With the damping affect，the system vibration becomes gentle. For the tension of lines, the peak value of dynamic tension of conductor can be times of the initial tension. It is shown that the proposed method is of efficiency and practicality.

The Prospect of Live-Line Overhead Conductor Replacement

While overhead transmission line conductors are traditionally replaced with the line de-energized, restringing has also been done with the line operating at full voltage and without interruption of load. This was done by providing a separate temporary phase position, supported by auxiliary structures, over the length of the pulling section, removing that phase position after stringing is complete. This procedure, successfully applied at 345 kV, requires a major presence on the right-of-way and, since the new conductor is pulled in close proximity to energized conductors carrying full load current, it also requires measures to mitigate potential hazards associated with voltages and currents coupled to the conductor being pulled. This paper proposes a new concept for full voltage, full load, in-situ re-conductoring; one which eliminates the need for a temporary phase position and likewise eliminates the need to accommodate currents and voltages coupled to the conductor being pulled. In the proposed method other safety issues, such as step-touch-transfer voltages and coupling to other equipment are no more severe that in more traditional live work. Through remote operation of both pulling and tensioning equipment, both operated on insulated platforms, the old conductor is used to pull in the new. Right of way access, other than at pulling terminals, is limited to replacement of conductor clamps with pulling sheaves and vice versa when pulling is complete; thus minimizing intrusion on the right of way. The proposed in situ method is based on a current transfer device (CTD) for conveying current from the conductor on the already restrung section onto the conductor being pulled and from the latter to the yet-to-be pulled section. The CTD makes use of a series of contactor wheels pressed against and collecting current from the moving conductor. Current flows from each contactor wheel to a fixed bus through mercury-based rotating contactors attached to the axle of that wheel. Such contactors are widely used in industrial applications. Stringing tension can be controlled within a band much narrower than the range of tensions accommodated by a line in actual service, thus allowing the process to respect minimum line-to-ground clearances. The method implies certain new safety precautions including high speed grounding switches at both pulling and tensioning terminals and sensors to detect broken conductors. If successfully developed, the method may provide a faster, more cost effective and less intrusive method for live conductor replacement.

Study of Dynamic Impacts on Transmission-Line Systems Attributable to Conductor Breakage Using the Finite-Element Method

The residual static load (RSL) is defined in the ASCE 74 standard as the loading criteria for a broken wire condition. However, a transmission line designed on the basis of the RSL may be unsafe because the RSL takes no account of the dynamic impact effect. This study develops a general finite-element analysis procedure to resolve the conductor breakage problem and to determine the broken wire load (BWL) for the transmission-line design. The developed procedure can account for the impinging and friction effects between the broken conductor and the ground. A three-span transmission line with the line configurations previously tested at full-scale was examined, and the results showed that the developed procedure could predict a realistic time history of responses. The developed procedure was then applied to a nine-span transmission line, and the results showed that the peak BWL was significantly greater than the RSL, indicating that the peak BWL instead of the RSL should be used to check the extreme load case for the conductor's breakage condition. DOI: 10.1061/(ASCE)CF .1943-5509.0000133. © 2011 American Society of Civil Engineers.

Development of Arc-Guided Protection Devices Against Lightning Breakage of Covered Conductors on Distribution Lines

The breakage of overhead covered conductors on distribution lines resulting from the short-circuit arcs caused by lightning flash becomes a challenge as the application of covered conductors increases on distribution lines. Based on various methodologies and devices developed to avoid the covered conductor breakage in the world, novel arc-guided devices, including arcing protection hardware with barbs, clamping post composite insulator, and barb electrode clamping post porcelain/composite insulator are presented in this paper. Experimental results are also presented to validate these new developed devices. Devices based on the developed technologies have been widely applied on the power grids in China successfully.

Compact Covered Distribution Lines Supported by Triangle Spacers: Spacer Design

Covered conductors and compact configuration with triangle spacers for 10-kV distribution lines have brought many advantages and benefits in China. In the past, the polymeric spacers cast with polycarbonate material had been designed and applied to make the distribution line compact. The reason that breakage faults occurred on compact distribution lines with polymeric spacer is because the polymeric spacers have bad pollution flashover performance, and the polycarbonate material used is not suitable for outdoor insulation. The pollution experiment of the covered distribution line supported by triangle spacers shows the flaw in the insulation layer is the key reason to generate flashover in a humid environment, which would be formed in the insulation layer of the covered conductor under sun radiation or under lightning effect. A new kind of triangle composite spacer, which is suitable for heavy pollution area, is designed to prevent breakage faults of covered conductors caused by leakage current. From the experimental results, the corona initial voltage and the flashover voltage of 10-kV covered distribution line fixed with composite spacers increased an average of 41.9% and 60.3%, respectively, comparing with the tested data of covered conductor fixed with polymeric spacers. The developed composite spacers can highly improve the pollution performance of 10-kV covered distribution lines. The field applications show the composite spacers are effective, and can prevent conductor breakage faults caused by leakage current.

Male copulation frequency, sperm competition and genital damage in the golden orb-web spider (Nephila plumipes)

Copulation in many sexually cannibalistic spiders is associated with a loss of function of the male reproductive organs and, as a consequence, males that survive sexual cannibalism may nevertheless be unable to subsequently copulate successfully. Sexual cannibalism is common in the Australian golden orb-web spider (Nephila plumipes), in which the tip of the conductor typically breaks during copulation. Thus, male mating frequency may be physiologically limited to two females, irrespective of the male’s ability to avoid cannibalism or the opportunity to locate and court additional, receptive females. Laboratory experiments revealed that the likelihood of the conductor breaking depends upon the copulatory history of the female insemination duct: males were more likely to break their conductor if they inseminated a ‘virgin’ rather than ‘mated’ insemination duct. However, the choice of insemination duct did not influence the duration of copulation or quantity of sperm transferred. In field populations, the proportion of males with both conductors broken increased during the course of the mating season, but while males with broken conductors did not copulate successfully with virgin females, they were nevertheless observed on the webs of immature females. We suggest that male N. plumipes with broken conductors on the webs of females are most likely mate guarding, as this appears to be the most effective mechanism of securing paternity.

A SEMI EMPIRICAL APPROACH FOR ESTIMATING DISPLACEMENTS AND FUNDAMENTAL FREQUENCY OF TRANSMISSION LINE TOWERS

Previously, it was found that the analytical deflections computed for towers using computer software are less than those from test results. The present study is aimed at deriving a relationship between the ratio of the test to theoretical deflection, and a nondimensional parameter to serve as an index for monitoring the structural displacements during testing. Currently, structural dynamic evaluation plays little or no role in the design of towers, partly due to the difficulties involved in the analysis and the relatively high cost of field testing. Using the fundamental frequency of a tower, the peak response of the tower to gusty wind and the impact force caused by conductor breakage can be evaluated. Both theoretical and experimental studies have been carried out to evaluate the natural frequencies of the towers tested at TTRS, SERC, Chennai, India. Based on these data, an equation was derived in this paper using the tower geometry and test/theoretical deflection ratios, which allows us to predict the natural frequency of the tower in a way closer to its actual value.

A case of abnormal overvoltages in a Petersen grounded 132-kV system caused by broken conductor

This paper analyzes stationary overvoltages in Petersen grounded systems resulting from a broken phase conductor. The analysis is done with basis in a real case where the overvoltages caused extensive damages and outages. It is shown that a requirement for high overvoltages to result is the combination of the following: The fault occurs on a radial connection that has substantial generation on one side only, the total compensation is close to 100%, and the compensation of the two subnetworks defined by the fault is far from 100% (one subnetwork is undercompensated and the other is overcompensated). These conditions were all met for the network subject to investigation. Overvoltages calculated by a simple model compare favorably with recorded results. The overvoltages are shown to be strongly dependent on the compensation level, the compensation distribution, and the shunt conductance to ground, and the load. A least squares method has been developed for estimating the shunt conductance based on a measured resonance curve.

A Case of Abnormal Overvoltages in a Petersen Grounded 132 Kv System Caused by Broken Conductor

This paper analyzes stationary overvoltages in Petersen grounded systems resulting from a broken phase conductor. The analysis is done with basis in a real case where the overvoltages caused extensive damages and outages. It is shown that a requirement for high overvoltages to result is the combination of the following: The fault occurs on a radial connection that has substantial generation on one side only, the total compensation is close to 100%, and the compensation of the two subnetworks defined by the fault is far from 100% (one subnetwork is undercompensated and the other is overcompensated). These conditions were all met for the network subject to investigation. Overvoltages calculated by a simple model compare favorably with recorded results. The overvoltages are shown to be strongly dependent on the compensation level, the compensation distribution, and the shunt conductance to ground, and the load. A least squares method has been developed for estimating the shunt conductance based on a measured resonance curve.

Ectomised conductors in the golden orb-web spider, Nephila plumipes (Araneoidea): a male adaptation to sexual conflict?

Male genitalia may facilitate sperm protection by acting as a plug that prevents or hinders future matings. The pedipalps (intromittant organs) of males of the orb-web spider, Nephila plumipes, have a conductor with a peculiarly curved ending and a triangular process near the terminal end. The tip of the conductor, including the process, breaks during most matings and remains inside the female genital tract. We explored the possible function of the conductor as a mating plug using the double-mating sterile-male technique. Our data are not consistent with a plug function because males use only one pedipalp in each mating, thus leaving an unobstructed insemination duct available for future matings; conductors of males mating with virgin females are not more likely to break than those of males mating with mated females, and second males show no preference for used or unused spermathecae. In addition, males that inserted their palp in the insemination duct that contained a tip of the conductor from a previous male obtained a share in the paternity of the female's clutch of eggs. Interestingly, the conductor is more likely to break if it is inserted in an unused spermatheca. We argue that several lines of evidence suggest that the conductor breaks as a result of intersexual conflict over the duration of copulation.

Broken conductors protection system using carrier communication

This paper presents a detection and signaling system designed to identify and locate high impedance faults caused by broken conductors on distribution primary feeders. Unlike conventional protection systems, which perform current sensing, the working principle of the proposed system consists on monitoring the voltage unbalance along a feeder. This allows the system to detect a fault occurrence even in cases when the conductor touches a high impedance earth surface (for instance asphalt). This system has an additional advantage of giving an indication of the location of a fault since it involves measurements at multiple points on a feeder. In order to detect the voltage unbalance produced by a broken conductor, a new sensor was developed which is sensitive to the electric field generated by primary feeders. A carrier communication channel is associated to each sensor allowing the high impedance fault occurrence information to reach the protection equipment located closer to or at the substation.

96/00494 A study of switching overvoltages on composite feeders-line-cable feeders

<dm:abstracts xmlns:dm="http://www.elsevier.com/xml/dm/dtd"><ce:abstract xmlns:ce="http://www.elsevier.com/xml/common/dtd" view="all" class="author" id="aep-abstract-id4"><ce:section-title>Publisher Summary</ce:section-title><ce:abstract-sec view="all" id="aep-abstract-sec-id5"><ce:simple-para id="fsabs035" view="all">This chapter discusses protection of power systems. The function of the protective equipment is to isolate the faulty plant from the running system by initiating tripping signals for appropriate circuit-breakers. It should therefore discriminate between faulty plant and sound plant carrying through-fault current. The whole process must be effected with the minimum of delay and disturbance. Exceptionally, some faults may be allowed to persist: an example is that of an earth fault on a system earthed through an arc suppression (Petersen) coil, or one having an isolated neutral, where the fault may be located and alternative feeds provided before the fault is isolated. Faults are due to insulation breakdown by deterioration, overvoltage, mechanical damage, or short-circuit effects; they may be simple or complicated, and involve conductor breakage or short-circuited turns on transformers or generators. The incidence of faults on cables and lines depends on the installation and the climatic conditions. The satisfactory operation of protective equipment (which extends from simple domestic sub-circuit fuses to sophisticated electronic system devices) depends on the co-ordination among fault megavolt-ampere levels, earthing, the availability of pilot cables, and the physical extent of the system.</ce:simple-para></ce:abstract-sec></ce:abstract></dm:abstracts>

Fretting fatigue in electrical transmission lines

One of the worst problems in overhead electrical transmission line fatigue is fretting, which can lead to wire failure or even conductor breakage at suspension clamps. However, fretting behaviour is extremely complicated owing to its synthetic geometry and loading condition. The tests concern bending fatigue on the overhead electrical conductor DRAKE. The imposed amplitude ranges from 0.60 to 0.80 mm. The static axial load was set at 25% RTS (Rated Tensile Strength). The tests were performed (including the static test) with a frequency of 10 Hz for any number of cycles. Post-test studies of the fretting scars were carried out by OM and SEM. Plastic flow, local wear and fretting cracking were observed at different conductor locations. Fretting cracking depends strongly on fretting regime, and the later propagation on the external load. Fretting regime and external load are determined by numerous factors such as contact type and position. Through metallographic examinations, it has been demonstrated that fretting is most likely to lead to cracks in the vicinity of the keeper contact edges, and probable propagation occurs at the upper half-section for the outer contact. The wire failure is found precisely in this zone and it fits our analysis well.