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R & D Review


No.95 June 1999

Development of "ECOSAFE", Ecological Wires and Cables

Recently, environmental problems are of great concern. Products must be designed under consideration for environmental pollution during operation and after its lifetime. To dispose electrical wires and cables, they are often burnt out or buried underground.
It has been pointed out that polyvinyl chloride (PVC) which is widely used as the jacket and insulation of wires and cables has the possibility of dioxin emissions during the burning process. Further, in the case of laying PVC, there is also a possibility of soil pollution led by the abstraction of lead included in PVC as a thermal stabilizer. Thus, PVC and its compound shoulder one of the environmental problem.
In order to keep the environment safe, ecological cables without PVC have been developed based on the conventional technology of halogen-free and flame-retardent (HF-FR) cables. Such ecological cables possess excellent flame retarding property and good processing compared to conventional cables.
Furthermore, the authors succeeded in developing weather-proof grade cables by using special light stabilizer. These cables contribute to supplying the colored wires and cables for outdoor use.
[Key words] Halogen-free, Flame-retarding, Weather-proof, Polyvinyl chloride, Polyolefin

Completion of 220kV Submarine Oil-filled Cable Project in Bahrain

In 1997, Mitsubishi Cable Industries Ltd. was awarded a full turn key contract by the Ministry of Electricity & Water (MEW), state of Bahrain for the supply and installation of 220kV submarine oil-filled cable circuits between the new Hidd power station facilities and the existing 220kV land oil-filled cable circuits at Manama. The intention of MEW is to obtain a stable power supply against the increasing demand on electrical power in Bahrain. Each circuit of project consists of 3.3km circuit length of 220kV submarine cables and 3.4km circuit length of 220kV land cables.
Prior to the manufacturing, the submarine cable and accessories were type tested at the manufacturer's factory under the witness of the consultant representative in accordance with CIGRE ELECTRA No. 171 and IEC 141-1. The submarine cables were manufactured in one continuous length and shipped to Bahrain by cargo vessel. In Bahrain, the submarine cables were coiled on the cable laying barge and installed at 1.3 meter below the seabed. The commissioning tests were conducted on the newly installed submarine and land cables before jointing to the existing 220kV cable circuits. These test were finally repeated on the complete circuits after the connection of the new cables to the existing circuits.
This project was successfully completed in March 1999 within the contract period only after 17 months from the awarding of contract.
[Key words] Submarine cable, Submarine oil-filled cable

Development of Compact Premolded Joints for 154kV XLPE Cables

Tape Molded Joints (TMJs) have mainly been used for the joint in the 154kV XLPE cable systems. Though TMJ is a compact and highly reliable joint, it requires long assembly time and high skills. The Premolded joint (PMJ) shortens the assembly time and requires no difficult skills. PMJ has been already applied to 275kV XLPE cable systems. We have also developed a more compact PMJ which can be used in ducts and manholes by adopting new material and new structure for the joint. As a result of doing a verification test it has been confirmed that it had enough performance as a connection part for 154kV.
[Key words] Compact accessories, Melting silica, Half-profit fixed metal fittings

Development of Fault Locator for Branch Line

Pulse radar and Murray- loop bridge are applied in cable fault location method for branch lines which require terminal connection at the far ends. This can be trouble some in fault location for branch lines. Moreover, pulse radar is applicable for only high resistance ground faults and Murray- loop bridge is applicable for only low resistance ground faults.
To improve the measuring apparatus, a prototype for current detection pulse radar method has been developed. The performance and confirmation test was carried out and its result is promising. Presently, the improvement study of more reduction of the location error is in progress.
[Key words] Fault Location, Discharge delay error, Pulse radar, Branch line

The Degradation Diagnosis of Polymeric Materials by Ultrasonic Waves
- Part 2, Development of the Ultrasonic Degradation Tester "U-023" -

Low voltage cables which have been used in various facilities for many purposes, require maintenance for stable operation as same as the high voltage cables. Until now, there was no effective methods to diagnose the degradation of low voltage cables non-destructively because almost all low voltage cables have no electromagnetic shielding layer. Instead, the megger test in which the insulation resistance between the couple of phase or that between each phase and earth has been applied for the diagnosis. However, the megger test requires service interruption and cannot be applied frequently because of its hindrance to continuous operation and high cost. Mitsubishi Cable Industries has developed an ultrasonic degradation tester U-023, which easily and non-destructively diagnoses the degradation of low voltage cables using the ultrasonic waves without any service interruption. In degradation diagnosis using ultrasonic waves the propagation properties of the ultrasonic waves in the surface layer of the cable sheath are measured which are converted into the breaking elongations. This is used as the degradation index of the sheath or insulation materials with database, which is explained in a previous paper. The ultrasonic degradation tester U-023 allows the degradation diagnosis of various materials such as various polyvinyl chlorides, polyethylene, crosslinked polyethylene etc., regardless of configurations or laying conditions of the cables. The U-023 gives not only the degree of degradation at that time, but also the degradation rate using richly stored database, therefore, the trend monitoring of the degradation of low voltage cables can be performed. By using the U-023 for regular inspections of low voltage cables, degree of degradation, the harshness of the surrounding environment and the time to change the cables can be estimated. The U-023 will be useful for the preventive maintenance for stable operation of plants and facilities.
[Key words] Low voltage cable, Polyvinyl chloride, Polyethylene, Crosslinked polyethylene, Degradation diagnosis, Ultrasonic waves

Development of Precipitation-Hardened Copper Alloy Trolley Wire(the second report)

Speeding up electric railways to increase the transportation capacity requires trolley wires with high strength, conductivity and excellent high-temperature strength, corrosion resistance as well as fatigue resistance. At the same time, the improvement of wear resistance is also required for maintenance. High strength trolley wire using precipitation-hardened copper alloy made by adding chromium and zirconium to oxygen-free copper has been developed to satisfy these demands as reported in a previous paper. This high strength trolley wire realizes remarkable increase in mechanical properties while maintaining high conductivity compared with tin added copper trolley wires and is being assessed in the commercial lines.
In this report, the status of the development and its assessment to practical use of this high strength trolley wire is reviewed together with the applicability of this trolley wire to the high-speed electric railways.
[Key words] Trolley wire,Copper alloy,High-strength,High-conductivity,Wear resistance

"T" type Solid Copper Basement Rigid Conductor with Trolley Wire

"T" type solid copper basement rigid conductor with trolley wire has been developed jointly with West Japan Railway Company and supplied to "JR Tozai-sen line", in operation from March 1997.
This newly developed conductor can be recognized as an epochmaking contact conductor structure since it requires neither special tool nor skill-technique during installation. Furthermore, it completelys excludes melt-down trouble of trolley wires, in comparison with the conventional types.
It can also be easily jointed and connected by bolting (: no skilled welding method required) because of its chemically and electrically stable component.
Furthermore, ionizing corrosion trouble due to underground water in tunnels can be completely eliminated because this conductor structure allows no galvanic reaction.
Consequently, "T" typesolidcopperbasementrigidconductorcansaveinstallationcost,and shorteninstallation time for the overhead conductor lines (power supply wire to motor car).
[Key words] Rigid conductor,Joint-splicer, Experimental installation, Bending moment and Deflection curve, Physical properties, Characteristic of standard

Study on Primary Coatings of Optical Fiber for High Speed Drawing

To find a suitable coating material (UV curable resin) of optical fibers for high speed drawing, the curing behavior of the primary coating under low UV doses and high temperature atmosphere were investigated.
As a result, we found that under conditions of low UV doses and high temperatures, the cure degree of the resin largely declines and that such declining degree matches the curing behavior of fibers drawn in high speed. We also found that under such conditions the curing degree is mostly determined by the oligomer of the resin.
By high speed drawing tests using the new resin which contains the most suitable oligomer, we proved that the coatings have sufficient curing degree even under drawing speed twice as fast as usual. We also confirmed that the fiber using the new coating had good fiber properties and long-term reliability.
[Key words] Optical fiber, UV curable resin, High speed drawing, Oligomer, Gel fraction, Cure degree

Development of Flat Flexible Erbium-doped Fiber-coil Sheets(EDF-sheets)

We developed flat flexible erbium-doped fiber-coil sheets (EDF-sheets). EDF-sheets are erbium-doped fibers (EDFs) arranged in a flat coil like alignment and laminated with resin for protection. The EDF-sheets we developed are one-layer-EDF-sheets consisting of a layer of short EDFs and two-layer-EDF-sheets which consists of long EDFs stacked in two layers. The thickness of EDF-sheets are the combined thickness of EDF coils and the laminating sheet. They are thinner than 1 mm and flexible.
We evaluated the EDF-sheets for their characteristics and found that there are no temperature reliance of the transmission characteristic caused by fabrication into flat coils or sheets. There were no difference in the spectral loss compared to EDF before fabrication into sheets and the amplification characteristics of the EDF-sheets did not deteriorate at the 1550 nm band. EDF-sheets have the same characteristics as the EDF, but has a smaller volume and can make the assembly of EDF amplifiers smaller and easier. EDF-sheets are expected to play an important role as optical devices for high-efficient compact amplifiers for communications.
[Key words] erbium-doped fiber, flexible, EDF amplifier

Optical Amplifier Plug-in Unit

Recently, optical amplifiers using erbium doped optical fiber (EDFA) have been in great demand. In this paper, we report on our newly developed EDFA plug-in unit, which can be installed in the communication bay.
This EDFA plug-in unit is composed of up to ten (10) EDFAs, power supply units, and a communication package.
EDFA mainly consists of EDF and CPU controlled 1480nm pumping laser diode and optical couplers/splitters. The EDF is specially designed to have zero dispersion at 1550nm and less non-liner effects. One can monitor and control the EDFAs from a remote PC via communication package.
We confirmed that the optical properties of the new EDFA are excellent and suitable for various field applications. Typical results are as follows :

  • Maximum optical output     15dBm
  • Small signal gain     33dB
  • Noise Figure     less than 6.9dB
  • PDG     less than 0.1dB(Typical 0.05dB)
  • PMD     62fs

[Key words] EDFA, Hi-PAS, EDF, Plug-in unit, Optical amplifier

Development of Flame-retardant Sealants for Sealing in Buildings

Sealants for sealing in buildings are used to fill up gaps between building materials, and to keep water and air tightness. Though flame-retardancy differs with the number of floors in a building, sealants on the market is combustible, and flame-retardant is a weak point. Therefore, the development of flame-retardant sealants was in much demand.
We have succeeded in developing flame-retardant sealants by applying the technology of flame-retardant polymer that has been cultivated so far. This sealant shows flame-retardancy for two hours without using any vice-material such as gaskets for joints in panels of buildings. As for the durability it shows excellent character which has been difficult so far with polyurethane materials.
By using this sealant, it is no longer neccessary to apply flame-retardant material over the gaps, thus allowing the reduction of material and execution fees.
[Key words] Sealants, Flame-retardant, Durability, Polyurethane

SUNELAST I- Fluorocarbon Elastomer with Chemical Resistance

Fluorocarbon elastomers have the highest heat, oil and chemical resistance in synthetic rubber. But because they dissolve or swell when they come in contact with particular fluids such as thinner, methanol, acetone, ethylene diamine, and sodium hydroxide, they cannot be used for seals.
SUNELAST I which we have developed has an excellent fluid resistance for the particular fluids listed above.
This paper introduces the new Fluorocarbon Elastomer SUNELAST I .
[Key words] Fluorocarbon elastomers, Oil resistance, Chemical resistance, SUNELAST I

Seals for Automatic Transmissions

There is growing demand for automatic transmissions in automobiles worldwide. For instance, the installed proportion is 80 to 90% in Japan and USA, it is also increasing in other areas. With the changes of the engines and others progress, technical requirements and operation conditions tend to be more severe demanding strict specifications for seals.
This report summarizes the technical characteristics of new seal compounds using acrylic and ethylene-acrylic rubber, seal bonded pistons which are rubber seals with stamping metal clutch pistons, plastic piston rings for rotational seals of the oil pumps in automatic transmissions.
[Key words] Automatic transmission, Seal, Seal bonded piston, Stamping piston, Seal ring

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