Cable Applications Research Articles

Development of a high-current HTS prototype conductor for power transmission

Extensive investigation, carried out worldwide until 1980, about the possible use of “conventional”, low-T c superconductors, in power transmission technology, had led to the unanimous conclusion that liquid-helium-cooled cables, though technically attractive, were not economically competitive with conventional systems unless extremely high, unrealistic, power levels had to be transmitted. The availability of HTS materials, potentially suitable for cooling with liquid nitrogen, has given an extraordinary impulse to revitalize widespread interest for such an application. Today, demonstration programs for HTS cable systems and system prototypes have entered the phase of experimental activity, with very positive results. Among the most recent advances is the successful manufacture of a machine-stranded, 50 m long, 3300 ampere HTS cable conductor, which was developed in the frame of an EPRI funded project focused on the potential application of HTS cables to retrofit and upgrade existing high-pressure, fluid-filled (HPFF) “pipe-type” cable circuits. The next, on-going, phase will be to complete the manufacturing of the cable and of the other components of the system. It is expected that these initial programs will be followed by pilot installations, which will provide the opportunity for establishment of relevant operational procedures .

Recent developments in HTS power cable applications

Practical investigations into superconducting power transmission applications have been initiated as a result of the discovery of high-temperature superconductors (HTS). These actions are presently following the parallel courses of materials and technology improvement and an increasingly detailed technical and economical analysis of superconducting power transmission applications within the system grid. Insofar as power cable applications are concerned, the most recent advances have been the manufacture of a machine-stranded, 50 m long, 3300 A HTS cable conductor and the detailed specification of several prototype HTS cable system installations. Many different HTS application options are being considered, each offering varied and distinct potential benefits to the electrical power industry. Some of these potential applications are already in development, while others are being systematically analyzed for compatibility with associated technical and economic evaluations.

Assessment of rock mass strength for underground excavations

Chemical grouts are used in a variety of application in civil and mining engineering, including strata sealing, ground stabilization, and support anchoring. Historically, cement-based grouts have performed effectively in cable support post-grouting applications in underground hard rock mines. Polyurethane grouts have been used in coal mines to stabilize poor roof or rib conditions and to mitigate problems associated with water inflows in shafts and tunnels. This paper focuses on the advantages of using an alternative, polyester-based grout instead of traditional grouting systems. A fundamental advantage is the fact that the polyester grout is safer than polyurethane because it does not contain isocyanate, which is recognized as a serious health threat. Laboratory investigations performed at Virginia Tech indicate that mechanical properties of the cured product are consistent with those of other grouts used in grouting applications where reinforcement and strengthening, together with deformability, are desired. Field tests performed in underground coal and limestone mines demonstrate the “pumpability” of the product and highlight several unique capabilities of the system, such as variable gel times and physical properties largely unaffected by water.

Development of a polyester-based pumpable grout

Chemical grouts are used in a variety of application in civil and mining engineering, including strata sealing, ground stabilization, and support anchoring. Historically, cement-based grouts have performed effectively in cable support post-grouting applications in underground hard rock mines. Polyurethane grouts have been used in coal mines to stabilize poor roof or rib conditions and to mitigate problems associated with water inflows in shafts and tunnels. This paper focuses on the advantages of using an alternative, polyester-based grout instead of traditional grouting systems. A fundamental advantage is the fact that the polyester grout is safer than polyurethane because it does not contain isocyanate, which is recognized as a serious health threat. Laboratory investigations performed at Virginia Tech indicate that mechanical properties of the cured product are consistent with those of other grouts used in grouting applications where reinforcement and strengthening, together with deformability, are desired. Field tests performed in underground coal and limestone mines demonstrate the “pumpability” of the product and highlight several unique capabilities of the system, such as variable gel times and physical properties largely unaffected by water.

Influence of surface modification of magnesium hydroxide on the processing and mechanical properties of composites of magnesium hydroxide and an ethylene vinyl acetate copolymer

Magnesium hydroxide is of increasing interest as an environmentally friendly flame retardant filler for ethylene vinyl acetate (EVA) copolymers which are widely used in cable applications. In this paper, magnesium hydroxide (Premier Periclase DP393) was used at a flame retardant loading of 60% w/w in an EVA copolymer with a vinyl acetate content of 18% (molar). The particular modifiers used in this study were stearic acid (converted to ammonium stearate (AS)) and γ-aminopropyltriethoxysilane (APS). The effect of surface-treated magnesium hydroxide on the processing, mechanical and the flame retardant properties were determined, together with characterisation of the interaction between filler and polymer. These studies have shown that, relative to the untreated filler, use of AS coating leads to a decrease in tensile strength to a limiting value at monolayer coverage, but an increase in elongation at break, which reaches a maximum at monolayer coverage. However, the APS treatment enhanced both tensile strength and elongation, relative to untreated filler, when used at levels in excess of monolayer. Characterisation studies suggest that this effect was related to the silane treatment promoting increased filler-matrix adhesion, and at levels greater than monolayer, promoting formation of a thick interphase and possible crosslinking of the bulk matrix.

A new era in cable designs and materials to resolve environmental issues

In recent years, environmental issues have had a profound influence on power cable designs and materials used in cable construction. This paper addresses the issues concerned with the effects of cables on the environment, as well as the effects of environmental conditions on cable performance and reliability. Effects on the environment include release of toxic materials and contamination of ground water. Environmental effects on cables are related to the presence of moisture, chemicals, ions, oils or solvents. All such issues must be considered in the evolution of environmentally-safe cables. This also extends to the manufacturing processes for producing cable insulation, jacketing and sheathing materials, as well as the cable manufacturing process itself. New cable designs and materials have been developed to mitigate many of the more serious environmental issues now associated with cable applications. Such designs and associated materials are reviewed in this paper. Emphasis is placed on the safeguards protecting the environment and on extending cable life and performance. These safeguards include technological advances in insulation, shielding, jacketing and sheathing materials, as well as new cable designs that cable specifiers should take into consideration when properly selecting and applying power cables for petroleum and chemical plant installations. Other user concerns that include cable diameter, short-circuit withstand, mechanical performance, installation, splices and terminations are briefly reviewed as they relate to current cable technology.

IEEE recommended practice for the testing, design, installation, and maintenance of electrical resistance heat tracing for commercial applications

Specific test requirements for qualifying electrical resistance heating cables for commercial service and a basis for electrical and thermal design are provided. Heater characteristics are addressed, and installation and maintenance requirements are detailed. Recommendations and requirements for unclassified heating cable applications are provided.

Limitations of short‐term ageing tests in assessing polyethylene blends for wire and cable applications

AbstractMedium‐density PE (MDPE) and high‐density PE (HDPE) compounds are commonly used in telecom wire insulation. Many of these compounds are blends of low‐density PE (LDPE) with HDPE in a ratio in which the two PE are immiscible. These blends feature very low mechanical properties that are often interpreted erroneously as being thermal degradation of the compound.

Connecting high-performance carbon-fiber-reinforced polymer cables of suspension and cable-stayed bridges through the use of gradient materials

Carbon-fiber-reinforced polymer (CFRP) cables offer a very attractive combination of high specific strength and modulus (ratio of strength or modulus to density), outstanding fatigue performance, good corrosion resistance, and low axial thermal expansion. The high specific strength permits the design of structures with highly increased spans. The high specific modulus translates into a high relative equivalent modulus. This factor is very important in view of the deflection constraints imposed on large bridges. A relative high modulus coupled with a low mass density offer CFRP cables already an advantage for spans above 1000 m. Since 1980 EMPA has been developing CFRP cables for cable-stayed and suspension bridges that are produced as assemblies of parallel CFRP wires. The key problem facing the application of CFRP cables, and thus their widespread use in the future, is how to connect them. A new reliable anchoring scheme developed with computer-aided materials design and produced with advanced gradient materials based on ceramics and polymers is described. Early 1996 such CFRP cables with a load-carrying capacity of 12 MN (1200 metric tons) have been applied for the first time on a cable-stayed road bridge with a 124-m span. Each cable is built up from 241 CFRP wires having a diameter of 5 mm.

Thermal and oxidative degradation of PE-EPDM blends vulcanized differently using sulfur accelerator systems

Blends of low density polyethylene (PE) of density 915 kg m − 3 and ethylene propylene diene rubber (EPDM) of density 860 kg m − 3 were vulcanized using two different sulfur accelerator curative systems: (A) a conventional curative system based on a combination of TMTD, MBTS and S; and (B) a silane curative system based on a combination of TMTD, Si69 and S. For each curative system, torque rheometric and morphological studies indicated development of a co-continuous phase morphology (involving hard PE and soft EPDM phases) for 30 70 PE/EPDM blend composition, particularly under dynamic curing conditions. Thermal degradation studies employing DSC and TGA indicated that sulfur vulcanization made the PE/EPDM blends thermally more stable. Between the two curative systems used, the conventional curative system imparted somewhat higher stability to the blend vulcanizate. Dynamic curing rendered the vulcanizates slightly more thermally stable than static curing under comparable conditions. Thermal degradation of the blend vulcanizates took place much faster at a relatively low temperature in air than in nitrogen. Studies of air oven aging of the blend vulcanizates enabled prediction of their life time in insulated cable applications at different temperatures. The predicted life time of 30 70 PE/EPDM blend vulcanizates at 70 °C (343 K) ranges between 10 and 15 yr.

A Comparative Study of the Fire Performance of Halogenated and Non‐Halogenated Materials for Cable Applications. Part I Tests on Materials and Insulated Wires

This paper, the first of a series of three, describes the results of an extensive study of the mechanical physical, electrical and fire properties of polymeric materials, both halogenated and non-halogenated, intended for cable applications. The objective of this study was to provide, by means of generally recognized standard tests, data, which should make possible a dispassionate fire hazard analysis of the relative merits of materials. Excellent materials were found with different chemical compositions. The results indicate the following: (1) Materials can be suitable for wire and cable applications irrespective of their chemical composition. (2) Halogen-containing materials, as a group, tend to outperform non-halogen materials in terms of the major fire properties: •Heat release •Ignitability •Flammability (3)Most commercial materials tend to have adequate mechanical and physical properties, but halogenated materials are, as a rule, slightly more satisfactory. (4)Compared to fire retarded non-halogenated materials, halogen-containing materials tend to have better performance in terms of some of the more important electrical properties, particularly dielectric breakdown voltage. (5)The resistance to ageing of non-halogenated materials is somewhat suspect, particularly with respect to attack by oils. (6)The smoke obscuration per unit mass of non-halogenated (polyolefin-based) materials is superior to that of vinyl-based materials, but differences are significantly reduced when considering the expected smoke obscuration in actual full-scale fires, due to the overall lower tendency of halogenated materials to burn; the smoke obscuration resulting from fluorinated materials is also low. (7)Smoke corrosivity is the single property where non-halogenated materials clearly outperform halogenated materials.

A Comparative Study of the Fire Performance of Halogenated and Non-Halogenated Materials for Cable Applications. Part I Tests on Materials and Insulated Wires

This paper, the first of a series of three, describes the results of an extensive study of the mechanical physical, electrical and fire properties of polymeric materials, both halogenated and non-halogenated, intended for cable applications. The objective of this study was to provide, by means of generally recognized standard tests, data, which should make possible a dispassionate fire hazard analysis of the relative merits of materials. Excellent materials were found with different chemical compositions. The results indicate the following: (1) Materials can be suitable for wire and cable applications irrespective of their chemical composition. (2) Halogen-containing materials, as a group, tend to outperform non-halogen materials in terms of the major fire properties: •Heat release •Ignitability •Flammability (3)Most commercial materials tend to have adequate mechanical and physical properties, but halogenated materials are, as a rule, slightly more satisfactory. (4)Compared to fire retarded non-halogenated materials, halogen-containing materials tend to have better performance in terms of some of the more important electrical properties, particularly dielectric breakdown voltage. (5)The resistance to ageing of non-halogenated materials is somewhat suspect, particularly with respect to attack by oils. (6)The smoke obscuration per unit mass of non-halogenated (polyolefin-based) materials is superior to that of vinyl-based materials, but differences are significantly reduced when considering the expected smoke obscuration in actual full-scale fires, due to the overall lower tendency of halogenated materials to burn; the smoke obscuration resulting from fluorinated materials is also low. (7)Smoke corrosivity is the single property where non-halogenated materials clearly outperform halogenated materials.

A single chip demodulator for 64/256 QAM

This paper describes a single chip demodulator for 64/256 QAM targeted to digital cable transmission applications. This chip incorporates specific novel functionality to mitigate channel impairments typical of cable transmission systems and consumer grade tuners.

A Comparative Study of the Fire Performance of Halogenated and Non-Halogenated Materials for Cable Applications. Part II Tests on Cable

A total of 21 electrical cables were made, all with essentially identical construction but differing in the chemical composition of sheath and/or insulation, which were all commercially available materials, both halogenated and non-halogenated. All cables were tested in two large-scale cable tray tests, ASTM D5424 (CSA FT-4 protocol), with a total length of 2.44 m and IEC 332-3, with a total length of 3.5 m. The cables were also tested in a number of small- and medium-scale tests for flame spread (IEC 695-2-2, IEC 332-1, UL 1581 Part VW1, BS 476 Part 12E, DIN 4102 Part 16), temperature increase (DIN 4102 Part 16) and smoke obscuration (IEC 1034-2, BS 476 Part 12E). Finally, all cables were tested in the cone calorimeter (ISO 5660), horizontally, at incident fluxes of 20, 40 and 70 kW m−2. All the cables passed the mild flammability tests, but distinctions could be made based on the afterflame time observed, where halogenated cables outperformed non-halogenated cables by a significant margin. It was also possible to distinguish between the halogenated and non-halogenated cables on the basis of the cable length charred in some tests. In terms of smoke obscuration, it was found that the rankings offered by the various tests were very different. While non-halogenated cables had improved smoke performance over traditional vinyl types, fluorinated cables performed very well. This confirms the importance of material selection by performance rather than by chemical composition. Almost all cables performed sufficiently well that they generated relatively limited amounts of smoke under realistic end-use fire test conditions. The peak heat release rate in the large-scale cable tray test (ASTM D5424) served as an excellent criterion for discriminating between the fire performance of the various cables (the traditional criterion being char length). The average rate of heat released also served to distinguish between different levels of cable fire performance. Moreover, cables passing the test tended to release less heat and smoke than those that failed. The trends observed in the cone calorimeter heat release test were similar to those in the large-scale test and show good correlation between cable tray char length and cone calorimeter heat release. It was observed that the halogenated cables tested performed better than the non-halogenated cables in terms of heat release rate by factors ranging from two to greater than five. The results indicate that cables with excellent fire performance can be constructed by using a variety of materials. It is thus important to specify fire performance and leave material choice to manufacturers.

A Comparative Study of the Fire Performance of Halogenated and Non‐Halogenated Materials for Cable Applications. Part II Tests on Cable

A Comparative Study of the Fire Performance of Halogenated and Non‐Halogenated Materials for Cable Applications. Part II Tests on Cable

Evaluation of cable bolt applications for Canadian underground mines

A market survey of all underground mines in Canada (Fig. 1) was complited to determine the extent to which cable bolts are being used as ground support. One hundred and nine questionnaires were distributed with 65% of them being retruned completed. As a result, the quantity, types and locations of cable bolt installations have been determined. In addition, the grout pumps used, time required and cost of installations have been addressed. The popularity of other support types used in underground mines summarized

Insulating and semiconductive jackets for medium and high voltage underground power cable applications

Insulating jackets extend cable life by retarding the ingress of water and soluble ions from the ground, minimizing cable installation damage and mitigating neutral corrosion. The physical properties of jacketing materials are discussed, along with the evolution of polyethylene jacketing compounds and the requirements of compatible red cable identification compounds.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Development of prefabricated joint for 275-kV XLPE cable

Application of XLPE cables to extra-high-voltage (EHV) transmission lines is expanding due to their excellent electrical properties and ease of maintenance, and 275-kV long-distance underground transmission lines are reaching the stage of practical utility. Extrusion molded joints (EMJs) are widely used as the XLPE cable joint for EHV transmission lines. However, EMJs have presented problems because of their insulation. They are formed on site through extruding and molding of crosslinkable PE like the cable, and need a long time for installation on site and higher jointing technique. The prefabricated joints (PJs), which are already applied to 154-kV transmission line, are installed on site by using the parts manufactured and tested in the factory, they require a shorter installation environment. This report introduces the results obtained regarding the improvement of the electrical property, workability and the performance of PJs, designed for 275-kV XLPE cable. These joints are planned to be used for 275-kV transmission lines from 1995. >

Recent advances in long length Bi-2223 HTS multifilamentary composite wire development

Developing applications for HTS technology are now enabled by a new generation of superconducting wires that bring together the required electrical and mechanical properties in long lengths that are durable when exposed to practical application environments. Advances in the development and scale-up of long-length Bi-2223 HTS composite wire are reviewed. Powder-in-tube processing was used to produce multifilamentary tapes in continuous lengths up to 1 kilometer. Electrical performance and uniformity results are reported for the wire in 300 meter and 1 kilometer lengths. Mechanical and environmental durability performance results are reported for multifilament wire tapes being developed for react-and-wind cable application as well as for wind-and-react coil and magnet applications. The use of these wires in practical demonstration applications is also reported. >

Performance summary of a 4,000 a high temperature superconducting cable conductor prototype

Multifilamentary superconducting Bi-2223 tapes made with a powder-in-tube process have been used to assemble multistrand, multilayer cable conductor prototypes. The electrical performance of these conductors has been evaluated at 77 K in self-field with DC and AC transport currents. Results show that these conductor prototypes, carrying up to 4,200 A DC, approach the 2,000 A AC operation threshold required for the commercial application of HTS power transmission cables. Combined with recent improvements in tape mechanical performance, stability, and long-length manufacturability, these results show the potential for use of HTS tapes in power transmission cables.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>