Bare Cables Research Articles

Health condition assessment of MV XLPE and bare cables. Case study

This paper proposes different models for the evaluation of medium voltage cables through a health condition analysis. For this purpose, several health indexes based on literature are evaluated in each model in order to provide a representation of the health condition of different types of cables. Finally the available empirical data is used in the proposed models for MV cables from ENEL COLOMBIA S.A. ESP.

Experimental testing and evaluation of coating on cables in container fire test facility

Fire tests were conducted on cables using fire-retardant paint employed in nuclear power plants that transmit electrical power, control and instrument signals. The failure criteria of various power and control cables coated with fire retardant coating at three different coating thicknesses (∼0.5 mm, 1.0 mm & 1.5 mm) were studied under direct flame test using Container Fire Test Facility (CFTF) based on standard tests for bare cables. A direct flame fire test was conducted for 10 min with an LPG ribbon burner rated at ten by fixing the cable samples in a vertical cable track. Inner sheath temperature was measured until ambient conditions were achieved by natural convection. The cables are visually evaluated for damage and the mass loss percentage. Cable functionality is ascertained by checking for electrical continuity for each sample. The thickness of cable coating on fire exposure is also studied by comparing the transient variation of inner sheath temperature along the Cable length. This study also evaluated the adequacy of fire-retardant coating on cables used for safety-critical equipment in nuclear power plants.

Three ‑ Phase Analysis of Active Losses on Conventional and Compact Distribution Networks

This study aims to analyze the performance under distribution networks, technically comparing the so called conventional distribution network (with bare cables) with those called compact distribution network (with covered cables). In old distribution lines bare cables has been used due the fact that its installation cost is cheaper than the covered ones. But nowadays almost of the distribution companies started to study the feasibility of the installation of compact distribution lines because of its benefits regarding maintenance and reduction of outages. Therefore, this research aims to analyze the technical losses of distribution compact networks when compared to the conventional distribution networks. For this purpose, electrical conductors have been modelled using ATP software and an algorithm for three-phase power flow calculation has been performed by the Newton - Raphson method, developed in MATLAB software. Three different topologies of distribution networks have been tested. Finally, with the simulation results it is concluded that the topology with the compact distribution networks configuration obtained a better performance among others.

Impulse withstand voltage of single-phase compact distribution line structures considering bare and XLPE-covered cables

This paper is dedicated to investigate the impulse withstand voltage of single-phase compact distribution line structures of 15kV class. The structures are tested in laboratory with the application of standard lightning impulse waveforms of positive polarity. Three situations are considered: (i) XLPE-covered cables with brand new insulation; (ii) XLPE-covered cables with punctured insulation; (iii) bare cables, aiming at assessing the critical case in which the insulating layer of the cable is completely deteriorated. The results indicate that the presence of an XLPE layer covering the cable leads to a significant increase in the impulse withstand voltage of the investigated structures compared to the use of bare cables. In the cases considering brand new XLPE-covered cables, insulation breakdown leads to the formation of a pinhole in the insulating layer at points up to about 200cm from the tested structure. The presence of pinholes in the tested cable specimens has no significant effect in the breakdown voltage of the tested structures, except when the pinhole is sufficiently close to the pole. Finally, to provide elements for investigating the performance of the structures when subjected to nonstandard impulse voltages, parameters for volt-time curves and for the disruptive effect (DE) method are provided for the critical case of structures with bare cables.

Analysis of electric field influence on buildings under high‐voltage transmission lines

High-voltage cables especially bare cables generate intense electric fields. Within certain distances, the fields could have strong effects on human health. Since of housing planning factors, it is inevitable that there will be buildings located under bare cables. Whether the intensity of electric field exceeds safety level (5 kV/m at 50 Hz) has been a concern for both land agents and residents. To address the concerns, this study studies the electric field of 500 kV overhead transmission line exerted on building and proposes the scheme for field intensity reduction. The authors study shows that when overhead cable and building are in different relative locations, the maximum intensity and influence range in the window regions can be highly variable, which suggests an optimal building orientation to minimise the electric field generated by overhead transmission lines. They also studied the field distribution in window regions on each floor in two models. The results provide design basis for safe distance between buildings and transmission lines. A shielding scheme for building construction is proposed to reduce the field intensity. Experiment result shows that with shielding on the building roof at a certain angle, the influence of electric field can be effectively reduced.

Design and Qualification of Joints for ITER Magnet Busbar System

The joints connecting the ITER magnet busbars and coils utilize the twin-box “shaking hands” concept: inside a helium leak tight box, a bare cable is pressed in an indium-tinned copper base. To form the joint, two boxes are tightly compressed against each other on the copper side with a layer of indium in between. This concept was chosen to address the different requirements of the joints: to provide low electrical resistance without degradation and need of maintenance during ITER lifecycle, to sustain cyclic electromagnetic and pressure loads, to be easily dismountable in case of failure, to be tolerant to manufacturing and assembly misalignments, to provide low coolant flow impedance, and to limit ac losses and at the same time to facilitate current redistribution in the busbars. This paper presents the design; the key results of the electromagnetic, thermal, and stress analysis; and the major manufacturing and qualification steps. The latter includes cryogenic fatigue test of the joint welds and joint resistance measurements.

A Quadruplet-Resonator-Based Ferrite-Free Choke for Suppressing Noise Currents on Cable Shielding

This paper presents a novel technique for suppressing cable noise currents, the quadruplet-resonator-based ferrite-free choke (QR-based FFC), to eliminate the gigahertz (GHz) electromagnetic interference caused by noise currents flowing on the cable shielding. This problem is difficult to handle with conventional ferrite materials since their permeabilities dramatically degrade when the operating frequency goes up to several GHz. In this paper, with the aid of QR surrounding on the cable shielding, the FFC forms bandstop responses against the noise currents. The corresponding equivalent lumped circuit model is proposed and investigated. Furthermore, the synthesis procedure is established using microwave filter theory. The QR-based FFC can achieve a high-level current suppression at the desired frequency band. This technology is experimentally verified: a given design example is demonstrated at the operating center frequency of 2.57 GHz. The frequency range of 3-dB current suppression is measured from 2.47 to 2.75 GHz (FBW $= $ 10.8%), where the highest suppression level is up to 36 dB. The FFC-added cable also demonstrates a good result in the reduction of far-field radiation, where the reduction level of radiation peak gain is measured as 7 dB compared with that of a bare cable.

The Method of 1394b Bus Transmission Cable Electrical Characteristics Testing

This paper presents a method of 1394b bus transmission cable electric parameters testing and provides a reliable way in selecting transmission cable. This paper introduces the IEEE-1394b protocol for transmission cable of electric parameters and requirements. We set up platform for 1394 cable testing, taking four kinds of 1394 bare wire cable and cable with Quadrax connector for dielectric withstanding voltage, differential impedance and so on. Using this test method can accurately reflect the 1394 cable’s electrical characteristics.

Fabrication and test of a racetrack magnet using pre-reacted Nb/sub 3/Sn cable

A racetrack magnet, using Nb/sub 3/Sn superconducting cable reacted before winding, has been fabricated and tested at Fermilab. It consists of two flat racetrack coils, connected in a common-coil configuration, separated by a 5 mm thick fiberglass plate. Synthetic oil was used to prevent sintering of the strands during the heat treatment. The coils were wound and vacuum impregnated in the mechanical structure. The turn-to-turn insulation, consisting of Kapton/spl reg/ and pre-impregnated fiberglass tapes as wide as the cable, was wound together with the bare cable in order to form a continuous inter-turn spacer. The coils were instrumented with voltage taps, temperature sensors, spot heaters and quench heaters. The maximum current achieved was 12675A which is 78% of the short sample limit at 5.1 K (minimum temperature in the coil during 75 A/s ramp). Measurement of the temperature margin revealed a low degradation in the innermost turns. Quench performances at different temperatures and ramp rate effects have been measured and are presented and discussed.

On the use of compliant fairings on conventional moorings

Abstract Compliant fairing made of plastic ribbons or flexible rubber filaments can be attached to the cables of taut‐line moorings to reduce the drag force of the currents. The efficiency of such fairing depends upon its orientation in the flow and the Reynolds number of the cable. Results of using filament fairing manufactured by ENDECO Inc. on a 337‐m long mooring in the mouth of Hudson Strait are discussed. The fairing was found to be detrimental in this application because of twisting of the wire rope, producing a “bottle‐brush” configuration, and because the normal drag coefficient Cd ? 2.5 ± 0.45 was found to exceed that of a bare cable by 65 per cent on average. The Reynolds number range for this drag coefficient was 2.6 × 103 to 4.2 × 103 and was determined by force measurements in a flume. It is concluded that the problems of correctly orienting the fairing in the flow, and the true drag coefficient for Reynolds numbers less than about 5 × 104 must be carefully addressed in the design of convent...

Comparative steady state deep towing performance of bare and faired cable systems

Abstract The measured drag characteristics of a variety of cable fairings are reviewed and compared with those of bare cables. The effect of cable inclination angle has been studied and an empirical rule developed for dealing with faired cables, the hydrodynamic properties of which are shown to depend significantly on the section shape of the fairing. Non-dimensional cable functions are tabulated for both bare and faired cable profiles and applied to show how the addition of fairings can improve the towing performance of a given system. Simple formulae are developed for calculating faired cable system properties and for assessing the effect of fish drag on the depression angle.

Announcement: 1971 Author and Subject Indexes

4 Skop, R. A. and Choo, Y., Configuration of a Cable Towed in a Circular Path/' Proceedings of the Symposium on Ocean Engineering, Univ. of Pennsylvania, 1970, pp. 3E1-3E24. 5 Crist, S. A., Analysis of the Motion of a Long Wire Towed from an Orbiting Aircraft, The Shock and Vibration Bulletin, No. 41-Pt. 6, Dec. 1970, Naval Research Lab., Washington, D. C., pp. 61-73. 6 Choo, Y., Analytical Investigation of the Three-Dimensional Motion of Towed Systems, D. Eng. thesis, 1970, Catholic Univ. of America, Washington, D. C. 7 Relf, E. F. and Powell, C. H., on Smooth and Stranded Wires Inclined to the Wind Direction and Comparison of Results on Stranded Wires in Air and Water, Rept. and Memo. 307, 1917, Aeronautical Research Committee, London, England. 8 Gibbons, T. and Walton, C. O., Evaluation of Two Methods for Predicting Towline Tensions and Configurations of a Towed Body System Using Bare Cable, Rept. 2313, Dec, 1966, David Taylor Model Basin, Washington, D. C. 9 Hoerner, S. F., Fluid Dynamic Drag, published by the author, 1965, Brick Town, N. j. 10 Long, M. E., Wind-Tunnel Tests of Mine Sweeper Cables, R-213, Dec. 1949, David Taylor Model Basin, Washington, D. C. 11 Pode, L., An Experimental Investigation of the Hydrodynamic Forces on Stranded Cables, Rept. 713, May 1950, David Taylor Model Basin, Washington, D. C. 12 Schultz, M. P., Wind-Tunnel Determination of the Aerodynamic Characteristics of Several Twisted Wire Ropes, Rept. 1645, June 1962, David Taylor Model Basin, Washington, D. C. 13 Gay, S. M., Engineering Techniques for Applications to Deep-Water Mooring, ASME Paper 66-PET-31, 1966. 14 Kochin, N. E., Kibel, I. A., and Roze, N. V., Theoretical Hydromechanics, Interscience, New York, 1965, pp. 329-332, 401-403. 15 Noonan, B. J., A Study of the Motion of a Cable System Towed from an Orbiting Vehicle, Ph.D. dissertation, 1971, Catholic Univ. of America, Washington, D. C.

Exploration of Transients by Switching Capacitors

Induced control circuit transients from energizing the first 230-kV shunt capacitor banks at Pinnacle Peak Substation damaged solid-state devices, caused flashovers at terminal blocks and initiated false supervisory control indications. Simulated, reduced voltage and full voltage switching of 230-kV capacitors were performed to explore the transient problem. The nature of the transient, its transfer mechanism to control circuits, how to reduce it at the source, and how to improve immunity of control circuits to the transient were studied. Simulation tests used actual power circuits in an inservice substation, which were impulsed at 20 kV. Reduced voltage tests were made on an isolated system at 30-50% voltage. Full voltage tests were made on a 230-kV interconnected system. Plastic-jacketed and lead- sheathed control cables and copper-braid- shielded coaxial cable specimens in a variety of grounding and shielding techniques were tested. Radio frequency, electromagnetic and electrostatic components of control circuit transients were measured separately. Transients up to 7,500 volts on unshielded cables were indicated, and frequencies-from 6-80 kHz and 0.4-7 MHz were recorded. Power circuit lumped parameter oscillations and distributed parameter propagation and reflection-type transient components were observed. Unshielded control cables were protected by grounding spare conductors and aluminum trench covers, paralleling two No. 4/ 0 bare ground cables, and installing 0.1 ?F bypass capacitors. Switches with 1 602 resistors per phase were used to suppress transients at the source. With these measures, control circuit transients were reduced to 65 volts for energizing 230-kV capacitors on an interconnected system.