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Due to the structure of underground cables, the frequency dependence of shunt admittances is more important to underground cables than to overhead lines. The main purpose of this paper is to establish a frequency-dependent underground cable model for advanced research and analysis regarding the influences of frequency-dependent shunt admittances on underground cable systems. The model will be more practical by adding the frequency dependence of shunt admittances into mathematical models and transferring them to the corresponding programming codes. In the cable Electromagnetic Transient Program (EMTP) models, the frequency dependence of shunt admittances could be represented by a set of equivalent circuits with constant parameters that can be determined by observing the characteristics of shunt admittances, then synthesizing them with a rational function approximation for discrete-time EMTP solutions. A number of simulation cases are presented in this paper to show that the frequency dependence of shunt admittances for underground cable systems leads to magnitude attenuation and strong traveling time reduction in a transient period of voltages. Also, the influences of frequency-dependent capacitances on cable systems are comparatively more impressive than those of frequency-dependent conductances. The conclusions are supported by numerical simulation results. Index Terms--Frequency dependence, rational function approximation, shunt admittances.

High frequency attenuation in shielded distribution cable is well understood; however, this cannot be said of transmission class solid dielectric cable, which has a more complicated structure, including additional semiconducting 'bedding' layers and a moisture barrier in the form of metal tape or corrugated metallic sheath. These additional elements cause new sources of high frequency loss relative to solid dielectric distribution cable. We report measurements of high frequency loss for transmission class solid dielectric cable with a corrugated copper sheath and for cable with a metal tape moisture barrier and wire screen (concentric neutral). Analytic approximations have been developed for the various sources of high frequency loss in these cable structures, and the analytic approximations have been checked using finite element analysis. Good agreement has been achieved between the computed and measured loss. Index Terms--High frequency attenuation, partial discharges (PDs), power transmission cables, solid dielectric.

The aim of this paper is to infer partial discharge (PD) detection limits in extruded cables as a function of the distance between PD source and detection point. The investigation is carried out for different types of detectors, from IEC 60270-compliant to ultra-wide bandwidth systems. For this purpose, a medium voltage cable has been modeled as a transmission line with frequency-dependent parameters accounting for skin effect, dielectric and semicon characteristics. Pulse propagation through the cable has been predicted for very long distances. Different filters have been used to simulate different detectors, emphasizing the behavior of these systems, particularly the features of sensitivity, noise rejection, PD source separation and PD source localization. Index Terms--Partial discharges, power cables, propagation, attenuation constant, semiconductive layers, IEC 60270, diagnostics, asset management.

Accurate location of the origins of partial discharges in power cable systems, based on arrival times, is imperative for the identification and assessment of defects. This paper evaluates different time-of-arrival algorithms in order to determine which method yields most accurate location under different circumstances. These methods are based on trigger level, Akaike Information Criterion, energy criterion, Gabor's signal centroid and phase in frequency domain. Several criteria are defined by which the algorithms are evaluated. These criteria include the sensitivity to noise, pulse shape and effect of load impedance. The sensitivity of the methods upon varying these quantities is evaluated analytically and by means of simulations. Further, the methods are tested on a medium-voltage cable system by injecting PD pulses in a cable with one joint. Each algorithm is applied to the measured pulses and the resulting location is compared with the known joint location. From the results the energy criterion method and the phase method show the best performance. Index Terms--Delay estimation, defect location, partial discharges, power cables, signal analysis.

This paper presents a new rigorous approach to the calculation of current ratings in pipe-type cables with slow circulation of the fluid. Detailed mathematical analysis is presented for the calculation of the hot-spot fluid temperature as a function of the cable geometry and the fluid inlet temperature. The emphasis is placed on real-time applications, in which the pipe-surface temperature is measured. A numerical example from an actual cable installation is presented. A comparison with the commonly applied method based on Buller's model is offered. Index Terms--Buller's model, pipe-type cables, rating calculations, slow fluid circulation.

The AC losses and current sharing in real YBCO cable are examined by constructing a 0.5 m long one layer cable. Findings reveal that the differences in contact resistances caused uneven current sharing between the tapes.

The stability of high temperature superconducting (HTS) power cable under fault current is examined. Findings reveal the determination of the stabilizer area for the practical HTS power cable for suppression of the bubble generation under the fault current.

The pressure drops and temperature increases of coolant in a DC-SC and AC-SC power cables are compared by fluid analysis. Results suggest the existence of high temperature spots in the LN2 conduit and that the pressure drop of DC-SC power transmission line (PT) is half of that of AC-SC PT.

AC losses in a tri-axial superconducting cable are examined. Results suggest that the axial AC loss strongly depends on the twist pitch, whereas the azimuthal AC losses are the same for all twist pitch.

The progress in the achievement of fine filament, low loss Rutherford cable superconductor for SIS 300 ring dipoles is discussed. Findings reveal the decline in conductor stability due to the increase in adjacent strand resistance.

In this paper, we use an integral formulation of the Maxwell's equations (magneto-quasi-static limit) in the presence of superconductors to analyze a resistive joint for cables of interest for controlled thermonuclear fusion. Index Terms--Edge elements, integral equations, superconducting cable joints, superconducting magnets.

Modeling of the manufacturing process of high-voltage power cables was performed with the aim of predicting residual stresses in the cable insulation. A viscoelastic power law-type constitutive model was used which incorporates temperature and crystallinity dependence of the parameters. In this way the mechanical problem is coupled to the heat transfer and crystallization problems. In order to illustrate the effects of relaxation, a comparison to a thermoelastic material model is made. POLYM. ENG. SCI., 45:1132-1139, 2005. [c] 2005 Society of Plastics Engineers, INTRODUCTION Cooling of polymer products is often a problematic manufacturing stage as it introduces residual stresses into the material. In particular, for high-voltage cable insulation the knowledge of such stresses [...]

A study is conducted to examine the several approaches for fabricating multistrand cables in which the Cu is added at cabling, stage of manufacture. The approach include mixed strand Rutherford-type cables with pure Cu strands cabled together with superonductors strands that have a low volume fraction of Cu, Cu added as a core to a Rutherford-type cable, and Cu strip added to the surface of the cable.

In medium voltage power cables, the concept of cost/reliability has been current since the end of the 1980s when the Brazilian Standards introduced ethylene-propylene-rubber (EPR) insulated cables, with different thicknesses of insulation for conventional cables and for those with blocked conductors or with water tightness constructions. However, despite the benefits obtainable by use of such cables, they have had limited use by electrical power utilities, perhaps because the concept has not become widely recognized. This paper intends to clarify and submit a new approach for design the dielectric system of medium voltage cables, for use in underground and insulated overhead distribution feeders. Theoretical aspects of sizing the dielectric system, by means of coordinating the insulation, and also using reliability parameters, will be dealt with herein. Results of practical applications are also presented and discussed. Keywords: Insulation coordination, MV Power Cables

The development of a Rutherford-type cable using multifilamentary Bi-2212 wires with a Ag/Ag alloy matrix is discussed. The Bi-2212 wires were successfully used for the fabrication of multistrand, kiloamp conductors that can be used to construct dipole and quadrupole magnets for particle accelerator applications. Future studies on cable critical currents will be conducted and compared for the different cable parameters studied in the experiment.

The termination design for a superconducting cable with a room temperature dielectric design is proposed. The restriction to cables with a room temperature dielectric design is based on the assumption that the cable-cryostat is on high-voltage potential. A current lead made of copper is required with a constant cross-section area. The termination is expected to have total losses ranging from 82 to 120 W at 0 and 2 kA, respectively.

The react-then-wind method is proposed for development of large magnet modules based on flexible reacted Nb3Sn cables. The flexible strands were constructed through the cabling of reacted strands and controlled heat treatment of unreacted cables. The cables did not exhibit critical current density degradation after bending. Results demonstrate the efficiency as well as the cost and engineering benefits of the approach.

Insulated and covered wires and cables have been used in aerial applications for over fifty years. Despite this long history, the design, application and operation of these different types of conductor constructions are frequently misunderstood and confused with one another. Utilities have increasing needs for greater reliability and higher quality of service, growing concerns over electromagnetic fields, increased difficulty in obtaining right-of-way and tree trimming, and difficulty in maintaining clearances in congested areas. These challenges have resulted in expanded interest in using covered or insulated cables in aerial systems. This paper (a) describes the differences between the constructions, (b) answers questions, concerns and misconceptions about these aerial designs, and (c) ranks the performance of each relative to desired attributes. A logical system for classifying covered wire and cable is proposed.

[Nb.sub.3]Sn forced flow cooled cable in conduit superconductors for fusion applications can be optimised for combinations of field, peak operating temperature and coil winding layout (pancake or layer) to give either maximum cable space current density or minimum superconductor cost. Conductor design for ITER including design criteria, choice of conductor configurations and its optimisation are discussed.

In order to fabricate a large-bore, high-field magnet which achieves a low coil weight and volume, a high strength compound superconducting wire is required. The alumina-copper strengthened [(Nb,Ti).sub.3]Sn wire which contained 30 vol.% alumina-Cu alloy fabricated by using the tube process has been developed and tested for critical current density, mechanical properties, transverse compressive stress effects and related properties. As a result, it was found that the reinforced [(Nb,Ti).sub.3]Sn wire had high transverse compressive stress tolerance, for example only 3% decrease which was 1/3 of the Cu matrix wire in [I.sub.c]/[I.sub.c0] at 60 MPa and reversibility in Ic between 0 and 200 MPa. Using the newly developed reinforced-[(Nb,Ti).sub.3]Sn wire, it will be possible to fabricate a lightweight, large-bore, high-field and compact superconducting magnet in the near future.

Conductor configuration and characteristics of superconducting cable for 50Hz a.c. use are reported. We developed a.c. conductors aiming low loss kA class current capacity. In consideration of reducing the current degradation by cabling, structures suitable for a.c. conductor are designed. In these conductors, low loss a.c. superconducting wires with very fine NbTi filaments are stranded around central cable of Cu-Ni or stainless steel wires for equal cooling condition, equal current distribution and mechanical reinforcing. Characteristics of small coils with these conductor at 50Hz a.c. load are tested and reported.

Large-current-carrying superconducting cable with sub-micrometer NbTi filaments has been developed for the application of AC power devices such as superconducting rotating machines, SMES and fault current limiters. The quench current and the loss under AC operation have been measured. The results show that the superconducting cable has AC transport current of at least 2000[A.sub.rms] at 50Hz in a 5T DC background magnetic field. The AC losses are measured to be 1.5x[10.sup.3] W/[m.sup.3] with 1000[A.sub.rms] transport current at 50Hz, which are remarkably low.

The [Nb.sub.3]Sn superconductor possesses a higher critical temperature than the NbTi strand. Therefore, it is now possible to make highly stable superconducting strands. We examined the manufacturing process of AC [Nb.sub.3]Sn strands. The internal Sn diffusion process showed a higher critical current density than the conventional process. [Nb.sub.3]Sn strands for AC use have a high Jc with low temperature reaction heat treatment, because they have fine filaments to decrease AC loss. We made a 400kVA class superconducting coil using the developed [Nb.sub.3]Sn cable with the React & Wind method. The loss density of this coil was 25.7MW/[m.sup.3] at the point just before the quench. In this case, the temperature of the cable increases about 3.39K. This means that the coil using [Nb.sub.3]Sn cables has a very high stability in AC use.

Two huge superconducting magnets are proposed for the future detectors of the Large Hadron Collider (LHC) at CERN: the ATLAS toroidal system and the CMS solenoid. Both designs are based on the use of large aluminium stabilized conductors, built from a cable coextruded with very pure aluminium and, in the CMS case, mechanically reinforced with aluminium alloy; these conductors are now developed by different manufacturers under research contracts handed by CERN. This paper presents results of the critical current density of both strands and cables at different stages of the conductor fabrication, the effect of different treatments on the aluminium residual resistivity ratio (RRR) and the characterization of the bonding between the cable and its stabilizer.

The optimization process for strand number and diameter, cable void fraction, and Cu/NbTi-ratio of the cable-in-conduit conductor for the superconducting magnet system of the planned stellarator fusion experiment Wendelstein 7-X is presented. Main optimization criteria are stability and cable cooling requirements, taking into account transient disturbances and losses. A simple stability criterion regarding transient disturbances is used which is derived from cable compression experiments. The resulting data for the 16 kA, 6 T cable are: cable and strand diameter [approximately equal to]11.5 mm and [approximately equal to]0.57 mm, respectively, strand number [approximately equal to]250, void [approximately equal to]36%, and Cu/sc-ratio [approximately equal to]2.7.

Multifilamentary [(Nb,Ti).sub.3]Sn super-conducting wires with reinforcing stabilizer of CuNb composite, CuNb/[(Nb,Ti).sub.3]Sn, were developed. Previously, we researched on the effect of reinforcement of CuNb composite as a CuNb/[(Nb, Ti).sub.3] wire and its stability by investigating the MQE (minimum quench energy). A test coil was fabricated using this reinforced wire without extra reinforcing material. The coil was produced by the 'react and wind method', then electromagnetic force for the wire was applied by charging electric current in the coil up to 11T. The coil was energized successfully and the generated electromagnetic force for the wire reached 224MPa at 136A and 9T without any degradation of test coil. These results proved that the bronze processed multifilamentary CuNb/[(Nb,Ti).sub.3]Sn have an excellent mechanical property, and a possibility to realize compact design of future superconducting magnet was confirmed.

Calculations have indicated that the simple macro composite conductor that comprises copper with a stainless steel sheath may be the best to use in high field pulsed magnets > 50 T. The recently commissioned wire fabrication facility of the Clarendon Laboratory can finish this type of conductors to the required size and cold work, after industrial preprocessing. The conductors have strengths in excess of 1.2 GPa. In this paper we describe the facility and the mechanical and electrical characterisation of the wires. We also report on our measurements of the temperature distribution in a macro composite wire during and after a typical pulse.