Materials Literature
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Investigations of the dielectric properties of SF/sub 6/, N/sub 2/ and mixtures have been carried out using a full scale model of a gas-insulated busbar (GIB). The breakdown characteristics under clean conditions are similar to those in a uniform field gas gap. The breakdown voltage is the maximum in SF/sub 6/ and the…
Partial discharges (PD) in void and electrical treeing were measured by using a computer aided measurement system. The results showed that the magnitude and the occurrence of PDs in voids were different from that of treeing PDs. Pulse-sequence-analysis and the PD distribution revealed the role of the instantaneous and…
The 60 Hz insulation loss current measurements in high voltage cable insulation containing water trees are described. To isolate the small insulation loss current from the significantly larger, quadrature (capacitive) current, a current-comparator-based high voltage capacitance bridge was used. It is shown that water…
Pre-selection tests on enameled copper wires to be adopted for windings of inverter driven rotating machines are generally performed applying quasi-square wave voltages to suitable specimens. This work experimentally investigates the influence of the factor "dv/dt" (or of the rise-time) characteristic of such quasi-sq…
We investigate the aging by UV radiation of silicone rubber used for outdoor insulators. Results from the measurement of surface potential decay by corona charging and of contact angle show a change of surface electrostatic properties and a slow decrease of contact angle under UV irradiation. For changes in the micro-…
Nowadays the increase of polluting loads in electrical networks affects supply voltage sinusoidality more significantly than in the past. Voltage distortion can decrease reliability of electrical devices, that is, increase their failure rate. This paper deals with the effect on aging acceleration due to harmonics for…
Comets, asteroids and other small bodies found in the solar system do not possess enough gravity to ensure spacecraft contact forces sufficient to allow many types of in situ science, such as core or surface sampling. Some method of providing sufficient contact force must be used for successful in situ exploration. A…
Effect of degassing treatment on tree initiation voltage was investigated in XLPE specimen with semiconducting electrode at 50/spl deg/C and room temperature. 1. Degassing treatment drastically increases tree initiation voltage of XLPE at room temperature. The same result is obtained in LDPE. 2. However, degassing tre…
Corona-stabilization in SF/sub 6/-insulated systems is a known phenomenon, but up to now not fully understood. In case of slow-rising impulse voltage stress, a stabilization mechanism, mainly depending on the steepness of the applied test voltage, occurs. Essential for the phenomenon is a space-charge accumulation in…
The competitive environment created by free market electricity supply requires that electric utilities reduce capital and operating expenses and, at the same time, increase the overall quality of electricity. Underground distribution cable systems are particularly sensitive to this need, which can be effectively addre…
This paper presents a new system designed for detecting the pulse-train electromagnetic waves emitted from partial discharge. The authors utilize a VHF wideband antenna array as electromagnetic sensors and calculate the time delay between them in order to locate partial discharge in 3 dimensions. The standard cross co…
This paper presents an approach having the purpose of obtaining charge mobility estimation from space charge measurement data, precisely from the depolarization (volt-off) characteristics provided by the pulsed electro-acoustic technique (PEA). General and approximate expressions are given for mobility calculation. Th…
We have analyzed the relative energy of nonmagnetic and magnetic low-lying electronic states of Ni atoms adsorbed on regular and defective sites of the MgO(001) surface. To this end cluster and periodic surface models are used within density functional theory. For Ni atoms adsorbed on oxygen vacancies at low coverage,…
The quasi-two-dimensional transition-metal dichalcogenide compounds $1T\ensuremath{-}\mathrm{Ta}{X}_{2}(X=\mathrm{S},\mathrm{Se},\mathrm{Te})$ at low temperature form charge-density waves (CDW), manifested in periodic lattice distortions. In order to investigate the effect of the CDW on the Fermi surface (FS) of these…
On-line partial discharge (PD) testing has been used for over 50 years to assess the condition of motor and generator stator winding insulation systems. In the past decade, advanced hardware and software have enabled superior methods of converting the PD data into practical information about the relative condition of…
The Jahn–Teller effect in the charge-ordered (CO) state for La1−xCaxMnO3 (0.5⩽x⩽0.87) was studied by measuring the low-temperature powder x-ray diffraction, internal friction, and shear modulus. We find that the electron–lattice interaction with the static Jahn–Teller distortion is the strongest near x≈0.75 in the CO…
Experimental results are presented to show that SMA actuators are able to control forces both rapidly and precisely. An antagonistic pair of constrained actuators is shown to be capable of rapidly changing the set-point throughout a /spl plusmn/7.00 N range. Although the system entered into a limit cycle at the set-po…
The site occupancy of manganese zinc ferrite (MZFO) nanoparticles is determined by a multiple-edge refinement of the extended x-ray absorption fine structure of the manganese, zinc, and iron absorption edges. The MZFO nanoparticles are generated by a reverse micellar synthetic route and compared to a ceramic standard.…
We present ion mobility measurements for small gold cluster cations, Aun+(n⩽10) in the temperature range between 77 and 300 K. While at room temperature all cluster sizes show only one sharp peak in the arrival time distribution, the Au9+ signal becomes bimodal at temperatures below 140 K. We interpret this unusual be…
A high-yield synthesis of atropoisomers of the meso-tetrakis(o-isonicotinoylamidophenyl)porphyrin was achieved. Depending on the crystallising solvent system, the α2β2 atropoisomer leads to the formation of either 1-D or 2-D coordination networks in the presence of Cu(OAc)2.