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Spring 1999 - Presentations

Check this page periodically to learn about the Technical Presentations scheduled for SC meetings.

Please Note: This is a only a listing of the presentations and DOES NOT IMPLY THE ORDER IN WHICH THEY WILL BE PRESENTED.

• Cable Construction and Design
  Monday, May 24th
  • Panel Session, Advances in Tree-Retardant Crosslinked Polyethylene Technology, Eric Marsden, Nova Borealis Compounds, Inc., Sundaresan Ramachandran, Union Carbide, and Haridoss Sarma, AT Plastics. Abstract: A review of the state-of-the-art technology by the leading compound suppliers of tree-retardant XLPE.
  • Evaluation of Jacket Materials and Configurations and Effect of Moisture Absorbing Materials on Preventing Water Tree Growth in Power Cables, S.E. Cherukupalli and Martin Colwell, Powertech Labs, Gino Valli, BC Hydro. Abstract: Polymer insulated medium voltage cables have experienced premature failures in-service, due in large part to water treeing. Research has shown that the initiation sites of these water trees are often located where there are stress enhancements at the insulation/semi-conducting shield interface and where water soluble contaminants permeate into the insulation. Material suppliers, cable manufacturers and users have introduced improved materials and cable designs as well as processing, manufacturing, transport, storage, and installation techniques that minimize contamination. Despite these advancements, gradual contamination can still occur due to the diffusion of ground water into the insulation. In fact, certain contaminants that are carried through the semicon/insulation shield interfaces tend to promote water tree growth. Manufacturers are now beginning to recognise this problem and have suggested the use of moisture resistant cables with jackets made of PVC, polyethylene or metal/polymer laminates along with underjacket water absorbing materials. This paper discusses the effectiveness of different jackets and materials and presents data on the effectiveness of water absorbing materials in delaying water permeation into the insulation. A simple and efficient cable-cell technique was developed which monitored the effectiveness of complete cable designs, by measuring the long-term water permeation resistance of short lengths of distribution class cables.
  • Comparison of Field Aging and Laboratory Aging, Carlos Katz, Cable Technology Labs and Wayne Banker, Orange and Rockland Utilities.
  • CANENA, Technical harmonization Committee, Robert Edwards, Alcan Cable.
  • ACLT Test Results on XLPE-Insulated Cable With Supersmooth Strand Shields - EPRI Test Program Update, Mark Walton, BICC Cables MTC. Abstract: Time-to-failure ACLT (accelerated cable life test) results at four different aging conditions are presented for XLPE-insulated cables with supersmooth strand shields . These results are compared with corresponding time-to-failure ACLT results for XLPE-insulated cables with conventional strand shields. After a review of a previously developed wet aging model for XLPE-insulated cables with conventional strand shields, a similar model is discussed for cables with a supersmooth strand shield.
  • Qualification Testing of 230kV Solid Dielectric Cable, Steve Campbell, PE, High Voltage Technical / Development Manager; Forte Power Systems, Inc; Abstract: Forte Power Systems has manufactured XLPE insulated HV cable with 800mils (20.3mm) of insulation an tested this cable at NEETRAC laboratories in Atlanta, Georgia. The test program included 40 heating cycles at 130 degrees C conductor temperature and testing of the cable at 230kV levels based on IEC draft standards.

  Tuesday, May 25th

  • The Design of Power Cables to Operate at High Electrical Stresses, R. N. Hampton, BICC Cables.
  • The Implications of High Frequency Loss in Distribution Cables, Steven Boggs, University of Connecticut.
  • Laboratory Scale Accelerated Aging of Extruded Dielectrics, R. Keefe, BICC Cables.
  • The Statistical and Physical Connections in the Testing of Polymeric Materials, Haridoss Sarma, AT Plastics. Abstract: Specific values of a given property can be obtained for crystalline materials and very well made amorphous systems. This is, however, not true for a semicrystalline polymer insulation such as XLPE. Polymers in general and polyethylene, in particular, are statistical ensembles for which only average value of a property could be measured or estimated. Appropriate statistical analysis of different measurements is therefore necessary. This presentation deals with measurements on polyethylene insulation compound giving specific examples of polymer characterization, manufacturing and electrical testing. The physical significance of different statistical parameters are outlined with the help of these examples.
  • The Influence of Semiconductive Screen Materials on Electrical Performance, R. N. Hampton and S.M. Moody, BICC Cables, Supertension and Subsea Cables and J. Freestone, BICC Cables, Abstract: Laboratory studies of tree initiation have been performed with a semiconductive needle embedded in a XLPE matrix. This arrangement creates a point-plane electrode geometry which more closely models the practical situation than traditional metal needle studies. This paper details the analysis of a series of tree initiation measurements which identify the important factors that the initiation voltage under both AC ramp and constant stress conditions. The key findings of the investigation are:
    • The important impact of semiconductive shields on the electrical performance
    • The interaction of the shields with the insulation: the optimum shield with one insulation may not be the optimum with another
    • The endurance response of the material combinations can be assessed using semiconductive needle tests
    • Material effects can be estimated from endurance measurements using the inverse power law approximation.
  • Implications of Poor Concentric Neutral - Ground Shield Semicon Contact in Shielded Power Cable, Steven Boggs, University of Connecticut. Abstract: In certain soils and for unjacketed cables, minerals can build up on neutral wires to the point that contact between the neutral wires and semicon is intermittent, resulting in cable failure. This can occur even when the semicon has been manufactured with ridges into which the neutral wires are buried at each ridge. Such a system must be modeled as a semicon which is connected to the neutral wires intermittently. The resulting RC circuit has frequency dependent properties which can cause large voltages between the semicon and neutral wires under surge conditions. The theory of such a system will be reviewed, along with transient finite element computations which allow the electric field amplitude and waveform between the neutral wires and semicon to be computed as a function of the distance from the last point of connection between the neutral wires and shield. The implications for and conditions under which such a problem will result in cable failure will be discussed.
  • The Effect of Aggressive Chemicals on Extruded Insulation Shields. John Densley, Ontario Hydro Technologies, Abstract: The paper describes the effects of aggressive chemicals such as wood-pole preservatives, gasoline and transformer oil on the properties of extruded insulation shields. Immersion in any of these liquids caused significant increases in the resistivity of the insulation shield to such an extent that the shield no longer confined the electric field within the extruded insulation. In all cases except gasoline immersed cables the increase in resistance was permanent. The effects of the resistance increases will be discussed.
  • Influence of the Conductor Shield Composition on the Performance of XLPE Insulated Cables Under Accelerated Testing, Evangeline Cometa, AT Plastics, Abstract: Different conductor shield compositions were used to manufacture 15 kV rated XLPE insulated cables. Accelerated tank tesing were performed using these cables. The estimated life time data was statistically analyzed. It is shown that the performance of the XLPE was enhanced significantly when specific additives are used in the conductor shield compositions. The type of carbon black seems to play a minor role in the cable performance under these accelerated testing.
  • High Performance Conductor Shields for High Voltage XLPE Power Cables, C.G. Reid, Union Carbide, Abstract: The extruded semiconductive conductor shield is a critical component of HV/EHV solid dielectric cables and affects the overall cable performance during the aging process. Semiconductive compounds designed specifically for these applications have superior interfacial smoothness, an absence of ionic impurities, and exhibit chemical inertness during the electro-thermal aging process.   The combination of these properties is found in acetylene black-based conductor shields prepared with advanced compounding technology.  In addition, these materials have polymers with suitable rheology for extrusion onto large conductors, and the formulation technology to assure performance during long term aging.  These key characteristics are shown to be responsible for improved cable performance properties in several different tests compared to commercially available conventional furnace carbon black-based conductor shield compounds.

   

• Accessories
  • New 138 kV Transition Joint from Low Pressure Oil Filled Cable to XLPE Cable, Milan Uzelac, G&W Electric. Abstract: General application of the joint, short description of the design, brief overview of installation procedure, design test results and some comments to current IEEE 404 standard.
  • Methods of Testing Separable Connectors - Rapid-Fire verses Sequential Switching, Roy Jazowski, Chardon Electrical Components, Inc. Abstract: Presently, the switching methods are not clearly defined in IEEE 386 and needs clarification in the next revision of this standard. This presentation will include revision suggestions.
  • Results Analysis of PD Testing at Colorado Springs, Kraig Bader, Colorado Springs Utilities. Abstract: (later)
  • Non-Destructive Diagnostic Testing of Distribution Cable Accessories, Willem Boone, KEMA, Abstract: After a brief introduction about purpose of diagnostic testing in relation to predictive maintenance, attention will be paid to the typical position of the splices in the distribution cable network: more defects and more suitable for PDD than the cable. Then a survey of test results will be given of VLF diagnostic testing in the framework of predicted maintenance of a utility in the Netherlands. The overwhelming majority of detected defects were splices. A few typical examples of test results and related defects in splices will be given. Finally a cost/benefit evaluation will show that this kind of diagnostic testing is saving money.
  • Technical Considerations for the Revision of IEEE Standard 404, C. Dang, Ph.D. Institut de Recherche d’Hydro-Quebec, Abstract: With more than two decades of existence since its inception at 1977, the IEEE std 404 had through many changes to reflect user’s concern as well as technological advances. Previous and recent test results on connector performance and material characteristics are presented and have suggested that some appropriate modifications are needed in the test method of connectors as well as in the aging test procedure of cable joints. It is proposed that connector should preferably be tested inside its cable joint housing for a better evaluation of its performance. Furthermore, aging test duration should also be extended to reach stability at cable joint interfaces. Finally, the test sequence should be modified to reflect more closely the real life conditions encountered in service.

     

     

• Cable Systems
  • Cable Failure Trends, Cable Management and Mitigation Analysis, David Flaten, Ultra Power Technology. Abstract: Cable failure rates for poly insulated cable are increasing nationwide. The trends can be extrapolated to show the ultimate failure rates a utility can expect based on present system condition and their cable replacement policy. Systematic cable management forms the basis for understanding failure trends, as well as costs and effectiveness of mitigation strategies.
  • Condition Assessment and Failure Modes of Solid Dielectric Cables in Perspective, K. Abdolall & G.L. Halldorson, Powertech Labs Inc., and D. Green, Syncrude Canada. Abstract: Older solid dielectric cables are now approaching the end of their life and failing. Consequently there has been a sustained effort for the development of techniques to assess the remaining life of in-service cables for the purpose of establishing replacement criteria. Because of the generally accepted belief that the failure mode is due to the aging of the insulation, these techniques have mainly focussed on measuring changes in the electrical properties of the insulation. However it has been determined that there are other failure modes associated with loss of the protective function of the jacketing material leading to corrosion and breaks in the metallic shields, causing arcing damage and eventual failure of the cable. This failure mode is more prevalent in cables operated in a harsh chemical environment.

    This paper presents the results of a research program aimed at developing a test protocol that is based on evaluating the condition of all the cable components and not just the insulation. The tests were designed to evaluate the following:

    • Condition of jacket
    • Extent of corrosion of the metallic shield
    • Degree of degradation of the cable insulation

    The results are discussed in terms of correlations between the field measurement parameters and the condition of the cable, and prioritization criteria for cable replacement.

  • Feeder Cable Explosion Investigation for BC Hydro, K. Abdolall, V.L. Buchholz, D.M. Cartlidge, C.P. Morton, Powertech Labs, G.B. Armanini, A. Harris,  G.F. Valli, BC Hydro. Abstract: This investigation was prompted by a cable fault and explosion inside a cable duct that housed a BC Hydro 15kV underground standby feeder cable. The incident occurred in September 1998 at a housing complex in Vancouver, British Columbia, Canada. Damage to the building vault was extensive and could very easily have resulted in severe injury or a fatality had anyone been in the immediate area of the vault. A failure analysis investigation revealed the explosion was fuelled by decomposition gases produced from the polymeric cable components because of a long duration, high impedance fault. Several unusual circumstances had to occur concurrently to allow the explosive conditions to develop as they did. The events that led to the explosion are discussed in terms of the failure mechanism of the cable and the effects of re closure arcing.
  • Matrix Methods for Determining Voltages and Currents in Cross Bonded 138 kV XLPE Transmission Circuits, Steven G. Lodwig, ComEd. Abstract: ComEd is replacing numerous older Self Contained Fluid Filled transmission cables with 138 kV XLPE transmission cables. The presentation will discuss design calculations for cross-bonded grounding of the new XLPE cable circuits including the effect of unequal phase currents and minor section lengths.
  • Recent Developments In Gas Insulated Transmission Lines, Dr. Herman Kock, Siemens A.G. Abstract: Several European countries believe that 400 kV gas insulated transmission lines are well suited for transmitting relatively large amounts of power through areas where it is difficult to obtain construction permits for overhead lines. Dr. Koch’s presentation will cover long term testing activities at EDF in France as well as activities by BEWAG in Berlin. His presentation will also cover possible ICC activities in this area.
  • On-Line in Service Partial Discharge Measurement and Location for Distribution and Transmission Type Cables. Zalya Berler, General Manager, Cutler Hammer. Abstract: The test method was designed for the Partial Discharge source location in the cables on-line. It is based on measurement of PD pulse time of arrival for two or more PD sensors located in different points. PD provides electromagnetic wave propagating along cable in two directions from a site of origination. This wave produce pulses electric and magnetic field and pulses current. PD current measurement is used for on-line measurement. A current induced into cable shield by propagating electromagnetic wave can be measured by Radio Frequency current transformers (RFCT). A charge transferred by the wave can also be estimated from pulse waveform. PD site locator is the instrumental and software tool specially designed for location of PD source in medium voltage bus ducts, transmission and distribution cables. It can be used on-line as well as off-line utilizing different PD sensors such RFCT, coupling capacitors, frame, etc. It uses controlled universal 4-channel oscilloscope with unique logamplifier of 80 dB. PD site locator acquires few hundreds of single pulses, proceeds data, detects pulses related to the discharge process and calculates a distance of pulse source from one of the sensors. The accuracy of detecting the location of PD source is about one foot. The minimal detected PD signal depends upon residual background noise and depends of the location of PD is over 5 pC. The technology applies for testing cable with T-connections

    
    

• Station, Control and Utilization Cables
  • Ampacity Testing of Maintained Spacing Cables Surrounded by a Fire Barrier System, Dhiren Savdharia, Southern California Edison. Abstract: The base cable ampacity values published in the ICEA/NEMA P54-440 for medium voltage cables in a ladder type cable tray, with maintained spacing between cables, are overly conservative. The existing standards do not provide guide lines for a tray that is surrounded by a fire barrier system and does not account for load diversity. This paper presents results of medium voltage cable ampacity tests conducted by Southern California Edison Co. A detailed analysis provides correction factors that can be used for ventilated punched bottom trays, solid bottom trays, covered trays, and trays surrounded by fire barrier systems.
  • 5kV Cable Failure, Rechad Zafar, Virginia Power. Abstract: Last year a fire, and a small explosion, took place in one of the Surrey Power Station’s diesel generator rooms. The diesel generator was undergoing periodic testing. The explosion occurred in the exciter compartment and it was contained within the panel. The faulted cables were #2AWG triplex aluminum conductor. The cable was installed 26 years ago. Examination of the interface between conductor and insulation on all phases showed evidence of melting and charring of the insulation with some adherence to the conductor strand. No signs of age related cable degradation were observed. The cables were replaced.

   

• Transnational Luncheon
  • High Stress XLPE Cables Using LEAN TM Technology, Nigel Hampton, BICC Cables. Abstract: Underground cable systems insulated with XLPE (crosslinked polyethylene), are increasingly employed for HV (33-132kV) distribution and transmission, in place of those employing self contained, low pressure, fluid filled (FF) paper cable for the following reasons:
    • simplicity in operation and maintenance, particularly important in remote locations,
    • elimination of fluid leakage risk.

    The continued rate of application of XLPE cables, has previously been limited by the low electrical performance of the cable and accessory insulations. The inherent high electrical strength of XLPE has been restricted by the achievable purity of the insulation material and the smoothness of the semi-conducting screens. High electrical strength is determined by the quality of the polymeric materials and by the process capability of the factory compounding plant and cable extrusion machines. To achieve a satisfactory service life, the insulation design stress of the first generation of 132kV XLPE cable in the UK was originally set at the comparatively low level of 6kV/mm, producing an insulation thickness of 19-21mm. An increase in design stress to 6.5kV/mm was made in 1994 for the second generation of cables, reducing their insulation to 18mm, however this was still significantly greater than the 8-9mm thickness for the equivalent FF paper cable. In consequence XLPE cables were still larger than paper cables in diameter and material volume, resulting in a significantly higher system capital cost, especially for longer circuit lengths, where the increased costs of the ancillary hydraulic equipment for FF cables is a smaller part. To address these issues the next (third) generation of cable system technology has been developed: LEANTM cables. The third generation of cable system technology is an integration of cable, accessories and installation methods utilising EHV technologies i.e. conductor designs, XLPE insulation and screen materials, metallic watertight barriers, oversheaths, accessories and installation techniques. These attributes enable the design stress for HV (33 - 150kV) to be lifted to 8kV/mm. Three 132kV LEANTM cable systems have been fully type tested in our laboratories and have been installed for East Midlands Electricity in Central England.

  • Cathodic Protection System for NYPA's 345kV SCFF Submarine Cables in Long Island Sound, Rusty Bascom, NYPA, Abstract: In 1992, NYPA commissioned a 13km 345kV SCFF submarine cable circuit across Long Island Sound. At the time of the cable design, corrosion was considered an issue, but a detailed study was delayed until the circuit had been in operation for a couple of years. In 1994, NYPA sponsored a project to study the impact of corrosion and corrosion processes on the submarine cables that provided some interesting results. The study lead to the manufacture and installation of a unique cathodic protection system that will be placed in operation later this month. The presentation will discuss some of the results of the initial study and a summary of recent project activities.
  • The International Scene, Willem Boone, KEMA
  • Jicable 2000 and the CIGRE Colloquium, Alain Pinet, EDF
  • 230 kV Cable Qualification Testing, Cashi Hashra, Southwire.

     

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