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We have determined, via electrophoresis, the zeta-potential at solid/non-polar liquid interfaces. The particles used were either metallic (Al, Ag, Pt) or non-conducting (capacitor paper, polyethylene) ones. The liquid was cyclohexane and its resistivity was modified by the addition of an electrolyte: triisoamylammonium picrate (TiAP). The zeta-potential and thus the electrical charge at the interface,...
Dielectric permittivity, ε′, and loss factor, ε″/ε′, of tert-butyl alcohol (TBA) have been measured in the temperature range from 282 K to 323 K and at spot frequencies 0.7,25,60 and 100 MHz in cooling and heating cycles. Refractive index and d.c. conductivity of the sample have also been measured. Both ε′ and ε″ exhibit a sharp transition at a temperature below its freezing temperature in the cooling...
Pre-breakdown phenomena and the breakdown strength of transformer oil with a model conducting macroparticle have been investigated, Plate electrodes with an area of from 5 to 154 cm2 were used. It has been found that hydrodynamic phenomena play a substantial role in the mechanism of the breakdown of oil. It has been proved that the purity of oil and the electrode area nave no influence on the voltage...
Non-uniform field gaps partially immersed in liquid coolants are essential components in any cryogenic or superconducting apparatus. We have investigated the dc, ac and impulse dielectric breakdown characteristics of non-uniform field gaps partially immersed in liquid nitrogen together with those completely immersed in liquid or cryogenic gaseous nitrogen. It is found that the Sumoto effect appears...
The paper presents examination results of the influence of thermal ageing and partial discharges on the capacity of transformer oil electrification, The examination has been carried out in a laminar flows region within the temperature range of 20–80°C with the use of flow pipes made of various materials.
Both a.c. and impulse breakdown voltages have been measured over a range of temperatures from 30 °C to 180 °C using lengths of commercial conductor insulated with cellulose or Nomex 410 tape and immersed in two low-flammability liquids, R-Temp and Envirotemp. The insulated conductors were tested either touching or with a 1 mm liquid gap between them. Impulse breakdown voltages for zero gap were found...
Measurements of the temporal variation of voltage and current in the spark discharge of liquid n-hexane were carried out. A dc-voltage, which increased linearly in time, was applied to a test cell with tip-plane electrode geometry. By careful mechanical design of the test cell a defined wave impedance of the whole experimental set-up was realized. A capacitive voltage divider was integrated into the...
The breakdown voltage versus gap length characteristics were obtained for degassed silicone oil, oil saturated with oxygen and oil containing varying concentrations of 1-methylnaphthalene as additive. Both aluminium and stainless steel electrodes were used. The breakdown voltage - gap characteristics for various additive concentrations in degassed oil all pass through a critical gap length at which...
A much refined experimental technique and analysis of measurements of dielectric breakdown in hydrocarbon liquids, in particular: n-hexane, has shown that the time lag distribution of an unperturbed liquid is governed by a Weibull probability function. Among dielectric liquids stressed at a constant electric field this is the first account of the applicability of the statistics of extreme values....
Hot electron effects in liquid xenon are quantitatively analyzed including electric field dependent drift mobilities and reaction rate constants (with SF6) and also conductivity relaxation following subnano-second pulsed ionisation. The interrelations between the effects are shown and a value of the electron energy exchange frequency of VK=(1.0±0.2)×109 (Te/T)0,5 s−1 at 165 °K is derived from experimental...
The effect, of conduction band formation on electron thermalization ranges bGP was determined from free ion yield measurements in coexisting vapors and liquids. Effects for spherelike (methane) and rodlike (ethane) molecules were compared. The density range was 0.14 ≲ d/dc ≲ 2.8. The density normalized range bGPd is inversely related to the energy loss cross section of epithermal (∼0.1–1 eV) electrons...
For the whole range of mesophase of anisotropic liquids such as pentyl-cyanobiphenyl (5CB) and octyloxy-cyanobiphenyl (80CB) the drift mobility of the ions have been determined, The time of flight method (the ions were injected from the electrode) and modifications of method of isothermic decays of currents have been applied. It has been found that the mobility is not dependent on the magnitude of...
This study deals with the kinetics of the field-dissociation effect in solutions of AOT surfactant in cyclohexane. The conductance increases with field strength as predicted by Onsager's theory, but large deviations from the Langevin relaxation time are observed at AOT concentrations greater than 10−3 Ml−1.
Electric field distribution including space charge effect is calculated by the Charge Simulation Method. From the analysis of conduction current expression, the conduction current in liquids is found to be caused by Schottky emission affected by space charge. Experiments and simulations are performed with needle electrodes of various materials (W, Cu, Mo and Ni) with various tip radius (3, 6, 10,...
The drift velocity of hot electrons in liquid Ar, Kr, and Xe near their triple points is studied using a Cohen-Lekner equation in which an inelasic depolarized electron scattering process is newly considered. The saturation of the drift velocity at the high field strength is appropriately explained. The magnitude and onset energy of the effective inelastic cross-section are compared with the experimental...
Using two different time-of-flight techniques (pulse voltage and V.U.V. photons pulse) ion mobility measurements have been performed, at room temperature, on a purified and direct 50 cSt polydimethylsiloxane silicone oil (Rhône Poulenc 604 V 50). These experiments have been carried out in a cell with plane parallel electrodes, for electric fields strengths ranging from 0.4 kV cm−1 to 8 kV cm−1 and...
Low-density regions developed in liquefied polyethylene with a point-plane electrode configuration under high electric fields have been investigated using a Schlieren technique in the temperature range from 120°C to 200°C. The region having a refractive index or a density lower than the surrounding medium is always formed near the point electrode irrespective of its polarity. For polyethylene in the...
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