Cable Loss Research Articles

Loss Characteristic Analysis of an HTS DC Model Cable Connected to a Model VSC-HVDC System

The purpose of high-temperature superconducting (HTS) cables as the transmission conductor in a high-voltage dc transmission system is mainly to reduce the Joule losses arising from the power transmission process. However, the harmonic currents generated from the switching behavior of the voltage source converters result in power loss in the HTS dc power cable. The cable loss characteristic should be analyzed in terms of its practical applications. In this paper, the harmonic currents characteristics were analyzed in both steady and transient state. An HTS dc cable model was also developed using the finite elements method to examine its loss characteristics. The results showed that the harmonic loss of the HTS dc model cable depends on the properties of the voltage source converters, the operating dc current level, and the ac system conditions. This work will be useful in studying the loss analysis of a real HTS dc power cable.

Time-Progressive Dynamic Assessment of Abrupt Cable-Breakage Events on Cable-Stayed Bridges

Although long-span bridges are usually designed with sufficient structural redundancy, particular concerns arise about the abrupt breakage of bridge cables, which may cause progressive failure such as zipper-like collapse. The time-progressive nonlinear dynamic analysis approach is proposed to investigate the abrupt cable-breakage event of a cable-stayed bridge. Compared with existing studies, the proposed methodology focuses on the simulation of cable loss scenarios in a more realistic manner through incorporating stochastic moving traffic loads, dynamic bridge–vehicle interactions, and associated dynamic initial states of the abrupt cable-breakage event. Several important issues associated with the proposed simulation methodology, such as the finite-element modeling option of cable breakage, different initial states of cable breakage, nonlinearity, and traffic loads, are investigated through a prototype bridge example. Finally, the response envelopes in terms of moments and stresses along the whole bridge are obtained and compared by means of the proposed nonlinear dynamic simulation approach, the static approach, and the pseudodynamic approach with a dynamic amplification factor of 2.0 as recommended by the Post-Tensioning Institute.

Quantitative Evaluation of Induction Efficiency in Domestic Induction Heating Applications

Efficiency of electromagnetic energy transference in coupled pot-inductor systems of induction cooktops is analyzed. The influence of different parameters such as pot properties, number of turns of the windings, frequency of the currents, cable types, and ferrite arrangements is studied by means of an analytical model. The proposed model is a combination of two independent models corresponding to the loaded planar coil impedance and the cable losses, respectively. The two models are related using the global magnetic field of the system. The analysis reveals that it is not possible to experimentally determine induction efficiency by measuring unloaded and loaded winding impedances. In this paper, we propose a practical method to obtain the induction efficiency and compare the results with theoretical predictions. Quantitative results corresponding to different pot materials, frequencies, type of cables, and ferrite arrangements are also presented.

A Study on Potential Progressive Collapse Responses of Cable-Stayed Bridges

In this paper, a finite element (FE) model for a cable-stayed bridge designed according to Australian standards is developed and analysed statically and dynamically with and without geometrical nonlinearities. The dynamic amplification factor ( DAF) and demand-to-capacity ratio ( DCR) in different structural components including cables, towers and the deck are calculated and it is shown that DCR usually remains below one (no material nonlinearity occurs) in the scenarios studied for the bridge under investigation, however, DAF can take values larger than two. Moreover, effects of location, duration and number of cable(s) loss as well as effect of damping level on the progressive collapse resistance of the bridge are studied and importance of each factor on the potential progressive collapse response of the bridgeis investigated.

Towards Solving the Problem of Transmission and Distribution of Electric Power in Nigeria via Superconductor Power Cables

Data on transmission and distribution losses in some African countries on conventional cables show that Nigeria experiences the highest transmission and distribution losses (=6.81 x 10 15 kWh) among African countries and, certainly, among the highest in the world with per capita consumption of 0.03 kWh/person. The total installation cost comparison between conventional and superconducting cables (SC) has been done and the comparison of the losses in SC cables and the conventional ones has also been analyzed. Some of the parametric properties of superconducting materials and benefits of high temperature superconducting (HTS) cables are discussed. Transmission lines in Nigeria have been found to experience high voltages and very low voltages under light loading and high loading, respectively. It has also been found that with the use of HTS cables, these losses, which are mainly the I2R losses, are negligibly small and almost zero. It is also found that HTS cables would be panacea for these high transmission and distribution losses in Nigeria. KEYWORDS : Transmission, distribution and superconducting cables.

Reemerging role of cable properties in action potential initiation

It is generally accepted that the axon initial segment (AIS), the neuroanatomical region linking cell body and axon, is the site of action potential (AP) generation in central neurons (1, 2). Because the occurrence, timing, and pattern of APs play critical roles in sensory encoding, motor output, and synaptic plasticity, the mechanisms underlying AP initiation are of fundamental interest. APs are initiated through membrane depolarization driven by the influx of sodium ions (Na+) through voltage-gated ion channels. The ability of Na currents to produce local depolarization depends on the ratio of the sources and sinks of current flow. Cable theory accounts for current flow down two distinct paths: (i) longitudinally along the central conductor and (ii) transversely through the cable sheathing or membrane. This theory, initially developed to understand signal losses in transatlantic telegraph cables, is also highly applicable to neuronal membrane compartments, such as axons, dendrites, and cell bodies (3, 4). For AP initiation, the source is Na current, and the sink is the loading resulting from current flow to adjacent membrane compartments, with both resistive and capacitive passive components. According to cable theory, either greater Na+ influx or lower passive load would increase membrane depolarization and favor local initiation. To date, the role of electrical load has been inferred from the results of computational studies, with little direct support (5⇓–7). In contrast, recent studies on AP initiation have focused on differences in the localized influx of Na currents. According to this view, a region of concentrated local Na+ influx endows the AIS initiation site with the lowest AP threshold. To evaluate the relative contributions of current source and electrical load in AP initiation, it is pivotal to determine whether the AP initiation site is the location of highest Na current …

Effect of the transmission configuration of wind farms on their capacity factors

This study conducted a feasibility study to analyze and improve the operational performance of two current onshore wind farms on the Changhua coastal area in Taiwan. We selected two adjacent wind farms A and B with similar wind-power density and geographical conditions; whereas, their main differences were the material of cables, the type of transformers, the number of cable branches, and the depth of buried cables. In actual operation states, the wind farm A had greater capacity factor than the wind farm B; therefore, the wind farm A was regarded as a base case, and two new wind farms 1B and 2B, resulting from the changes in the cable materials, transformer types, cable branches, and buried cable depth of the wind farm B, were proposed to assess the feasibility of system improvement. Results showed that the material of cables, the type of transformers, the number of cable branches, and the depth of buried cables were the crucial factors of affecting the efficiency of wind farm B. Shallow cabling increased the temperature of cables, higher temperature causing a decline in cable capacity, and this phenomenon was crucial to aluminum cables rather than copper cables. The results of comparing the wind farms 2B with B indicated that the maximal transmission loss of cables was reduced by 6.4GWh/year, and the maximal annual CO2 emission was reduced by 4.5kt/year. Additionally, the increased cost of transformers and cabling was recovered in 2.12years, when the wind farm B was modified to 2B before construction.

Effects of Harmonics on Power Loss in XLPE Cables

Harmonics in power systems is increasingly at high level. Also, there has been an incredible growth in the use of cross linked polyethylene (XLPE) cables in distribution systems. Harmonics cause additional power loss/temperature rise; causing premature failure of cables. Catastrophic failure of power cables leads to great inconvenience to consumers and loss of system reliability and money. To avoid the overheating of power cables; the additional power loss due to harmonics should be accurately calculated and properly accommodated by derating the cable. The present method of calculating the power loss in cables in harmonics rich environment is very arduous. The aim of this paper is to present the reasonably accurate method for evaluating effects of harmonics on the power loss in XLPE cables. Computational model is developed in MATLAB for power loss calculation using conventional method. Using this model, calculations are performed for aluminium and copper conductor XLPE cables of different size and type; for three different types of harmonics spectrums having total harmonics distortion (THD) of 30.68%, including all odd harmonics components up to 49th order. Using these results; a mathematical model in the form of simple empirical formula is developed by curve fitting technique. The results obtained by various models are presented and compared with error justification.

A flexible polyimide cable for implantable neural probe arrays

A flexible polyimide cable developed for implantable neural probe array application is presented. The flexible cable is used to connect two implantable platforms--one in direct touch with the brain containing a neural probe array and its interface IC, and the other on the skull including a wireless link IC, a coil and an antenna for power and data transfer through the transcutaneous link. The cable needs to be highly flexible to minimize post-insertion injury caused by the probe array in the presence of brain micro-motion. Polyimide is used to form a flexible substrate and an insulator layer of the cable. For the advanced neural recording system, a large amount of neural recording data has to be communicated between the two platforms through the flexible cable. High-rate data transmission performance of the fabricated flexible cable is characterized and discussed. The measured insertion loss (IL) of the flexible cable is less than 3 dB and the isolation between two adjacent interconnects is better than 17 dB up to 2 GHz. The data transmission through the flexible cable is verified to be highly reliable at 100 Mbps. For surgical manipulation and long term implantation of the neural probe microsystem, the flexible cable needs to have excellent mechanical strength and resistance to fatigue. The mechanical characteristics and fatigue strength of the flexible cable are also measured and discussed. The measured maximum tensile stress and strain of the flexible cable before failure are 251.2 ± 7.1 MPa (14.35 ± 0.3 N) and 4.16 ± 0.11 %, respectively. The Young's modulus of the fabricated flexible cable is 8.21 GPa. From the fatigue strength testing, the measured resistance change of the flexible cable's interconnect is less than 4.8 % after 250,000 cycles of cyclic mechanical stretch.

The heated infinite cylinder with sheath and two thermal surface resistance layers

The temperature evolution in and around a heated infinite cylinder with tubular sheath is studied, allowing for surface resistances between the cylindrical core and sheath, as well as between the sheath and surrounding medium. This configuration was initially investigated in the framework of the thermal conductivity measurements made by the Apollo 15 and 17 missions to the Moon. Only the equilibration case was used in this context. We derive corresponding equations for arbitrary active heating of the cylinder core and sheath. Typical applications are the determination of the temperature increase and the heat loss of buried cables, and the temperature evolution in thermal conductivity sensors. An example of the latter is used to illustrate some consequences of low surface conductances.

Transient Analysis of Large Scale PV Systems with Floating DC Section

The increasing penetration of renewable sources with power-electronic interfaces in power systems is raising technical problems and the overall efficiency of photovoltaic systems can decrease dramatically. In this context, the optimal layout for the photovoltaic system is required. The most adequate strategy to connect the renewable system to the electrical power grid or to supply the end users must be adopted. The present paper proposes a design layout of a PV plant using a DC bus system to improve the overall energy conversion efficiency. An analysis of steady-state system stability, voltage drop and DC cable conduction losses is conducted. The leakage currents to the ground are investigated through simulations. Experimental results are shown focused on the analysis of optimal layout of photovoltaic systems under particular operating conditions.

Regulation of the formin Bnr1 by septins anda MARK/Par1-family septin-associated kinase

Formin-family proteins promote the assembly of linear actin filaments and are required to generate cellular actin structures, such as actin stress fibers and the cytokinetic actomyosin contractile ring. Many formin proteins are regulated by an autoinhibition mechanism involving intramolecular binding of a Diaphanous inhibitory domain and a Diaphanous autoregulatory domain. However, the activation mechanism for these Diaphanous-related formins (DRFs) is not completely understood. Although small GTPases play an important role in relieving autoinhibition, other factors likely contribute. Here we describe a requirement for the septin Shs1 and the septin-associated kinase Gin4 for the localization and in vivo activity of the budding yeast DRF Bnr1. In budding yeast strains in which the other formin, Bni1, is conditionally inactivated, the loss of Gin4 or Shs1 results in the loss of actin cables and cell death, similar to the loss of Bnr1. The defects in these strains can be suppressed by constitutive activation of Bnr1. Gin4 is involved in both the localization and activation of Bnr1, whereas the septin Shs1 is required for Bnr1 activation but not its localization. Gin4 promotes the activity of Bnr1 independently of the Gin4 kinase activity, and Gin4 lacking its kinase domain binds to the critical localization region of Bnr1. These data reveal novel regulatory links between the actin and septin cytoskeletons.

Analytical efficiency evaluation of two and three level VSC-HVDC transmission links

An analytical method to calculate the efficiency of VSC-HVDC links based on two-level and three-level VSCs is presented. The method uses the average and root mean square of the VSC converter current to estimate the conversion losses in the converters (conduction and switching losses). The remaining power losses (DC cable transmission losses due to I2R, the losses in the coupling transformer, and AC harmonic filter losses) are evaluated using conventional well-known methods. Results obtained analytically are confirmed by digital simulations.

Structural behavior of the suspen-dome structures and the cable dome structures with sliding cable joints

Sliding cable joints have been developed for the cable dome structures and the suspen-dome structures to reduce the cable pre-stressing loss and obtain a uniform inner force in each hoop cable. However, the relevant investigation is less addressed on the structural behavior of the cable dome structures and the suspen-dome structures with sliding cable joints due to the lack of analysis techniques. In this paper, a closed sliding polygonal cable element was established to analyze the structural behavior of the cable dome structures and the suspen-dome structures with sliding cable joints. The structural behaviors with sliding cable joints were obtained.

Prevalence and Predictors of Cable Extrusion and Loss of Electrical Integrity with the Riata Defibrillator Lead

Recently, a medical advisory was issued regarding the Riata and Riata ST silicone endocardial defibrillator leads (St. Jude Medical, Sylmar, CA, USA) addressing the issue of conductor cables extruding in an "inside-out" fashion from the main body of the lead. However, little data exist to guide our management of patients with these leads. A retrospective analysis was performed of 84 patients with a Riata lead who underwent cine-fluoroscopy and electrical evaluation as part of a screening program to assess for cable extrusion. All leads screened were dual-coil except for one single-coil lead. Of 84 patients, 23 patients (27.4%) had fluoroscopic evidence of cable extrusion. Multivariate analysis showed that the duration of time since lead implant and the presence of multiple right ventricular leads were significantly associated with cable extrusion. All 23 patients had normal electrical parameters on routine device interrogation. Fifteen of these 23 patients (65%) with extruded cables had high-voltage shocks within 12 months of lead screening; only one patient demonstrated postshock electrical abnormalities. The prevalence of cable extrusion in dual-coil Riata leads is significantly higher at 27.4% than previously reported. The duration of time since implantation and the presence of multiple right ventricular leads are associated with cable extrusion. High-energy shocks did not reveal electrical abnormalities in most patients with cable extrusion.

Loss Characteristic Analysis of HTS DC Power Cable Using LCC Based DC Transmission System

The zero resistance of superconducting material is observed only with a DC current, while transmission loss occurs with an AC current. Power converters use electronic devices which generate harmonic currents due to their high switching frequency. The authors expect that harmonic currents also influence the losses in the superconducting DC power cables of a DC transmission system. The authors have developed a miniaturized superconducting DC transmission system with 12 thyristors based AC/DC converter and a 2 m length superconducting cable connected to the DC side between two converters. The capacity of the converter is 20 kW and the critical current of the HTS DC power cable is 140 A. In this paper, the HTS DC power cable loss characteristics were anal- ysed by the fabricated home-made thyristor converter system.

Analysis of Cable Force Loss of Prestressing Structure during Tension Construction

Suspen-dome structure is a new type of large-span space structure, however, cable force loss at the joint during prestressing construction becomes big issues. To solve this problem, study has been done on this issue. ANSYS finite element software is used to simulate friction at the joint and its effects on cable force distribution and overall performance of the structure. Further analysis of reduced scale model test has been done, of which the results meet well with the theoretical calculation results.

Comparison of various procedures for progressive collapse analysis of cable-stayed bridges

Alternate path (AP) method is the most widely used method for the progressive collapse analysis, and its application in frame structures has been well proved. However, the application of AP method for other structures, especially for cable-stayed structures, should be further developed. The four analytical procedures, i.e., linear static, nonlinear static, linear dynamic, and nonlinear dynamic were firstly improved by taking into account the initial state. Then a cable-stayed structure was studied using the four improved methods. Furthermore, the losses of both one cable and two cables were discussed. The results show that for static and dynamic analyses of the cable-stayed bridges, there is large difference between the results obtained from simulations starting with either a deformed or a nondeformed configuration at the time of cable loss. The static results are conservative in the vicinity of the ruptured cable, but the dynamic effect of the cable loss in the area farther away from the loss-cable cannot be considered. Moreover, the dynamic amplification factor of 2.0 is found to be a good estimate for static analysis procedures, since linear static and linear dynamic procedures yield approximately the same maximum vertical deflection. The results of the comprehensive evaluation of the cable failure show that the tread of the progressive failure of the cable-stayed bridges decreases when the location of the failed cables is closer to the pylon.

Optical Intensity-Type Refractometer for Remote Measurements Via Fiber-Optic Cables

We present a fiber-optic refractometer with intensity-type transducer which can operate remotely via long fiber-optic cables. This version of the refractometer is intended for accessing the concentration of aqueous solutions of sodium chloride in the range from zero to about 145 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> / <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> (1.327 <; <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> <; 1.353 at λ = 940 nm and 25 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C), which is of significant practical interest for industrial users. We address the relationship between the span and linearity of the intensity-type optical transducer with spherical working surface which we employ in the refractometer. We optimized the transducer for the specified measurement range and achieved good sensitivity and non-linearity as small as 0.05. We significantly reduced the negative effect of the unstable optical loss of the fiber-optic cables, variation of the optical source power and photo-detector response on the readings of the refractometer by using an optical bridge configuration followed by an analogue optoelectronic signal processing unit. The refractometer has a parasitic variation of its output as low as 1.5% under a total variation of the optical source power and a fiber-optic cable loss of 20 dB. Potential applications of this refractometer include the in-situ characterization of various liquids such as the sodium chloride salt-brine solutions in food industry.

AC loss reduction of outer-diameter-fixed superconducting power transmission cables using narrow coated conductors

AC loss reduction of superconducting power transmission cables is of great importance to promote their application in power grids. To meet certain installation conditions, cables are required to be designed with fixed outer diameters. This paper focuses on outer-diameter-fixed monolayer and multilayer (2-layer and 4-layer) superconducting power transmission cables constructed with coated conductors. Detailed numerical analysis of their AC loss reduction by replacing generally used 4-mm wide coated conductors with 2-mm wide narrow ones are presented. A 2-D FEM numerical model was developed to calculate AC losses of the cables. For detailed and comprehensive analysis, a series of variable parameters, such as number of layers, critical current density (Jc) distributions of coated conductors and load rate, are varied at well selected values to study their influences on the AC loss reduction. It is obtained and testified that 2-mm wide narrow coated conductors can effectively reduce AC losses in both monolayer and multilayer cables, even though more gaps are introduced. The knowledge presented is helpful for designing and fabricating practical cables.