Yukio Kito

Total voltage drops in electrode fall regions of , argon and air arcs in current range from 10 to 20 000 A

Measurements were made of the sum of cathode fall and anode fall voltages, i.e. electrode fall voltages for , argon and air arcs at a pressure of 0.1 MPa in wide current range from 10 to 20 000 A. For each arc, copper - tungsten, copper, iron and tungsten were used as electrode materials. The arcs proved to have electrode fall voltages of 17.5, 17.5, 17.5 and 13.8 V at the Cu - W, Cu, Fe and W electrodes respectively. The electrode fall voltage of each arc was affected by the electrode material. It was also found that the electrode fall voltage of each arc at a given electrode was independent of current in the above range. Further, the electric field strength at cathode surface and thickness of cathode fall region were estimated on the basis of Temperature-and-Field emission theory.

γ-Radiolysis of D-glucose in aerated, aqueous solution

Gamma-Radiolysis of D-glucose in aerated, aqueous solution gives mainly D-glucono-1,5-lactone, D-arabino-hexosulose, and D-ribo-hexos-3-ulose, together with D-xylo-hexos-4-ulose, D-xylo-hexos-5-ulose, and other pentose, tetrose, and triose derivatives as minor products, which were estimated by mass spectrometry of their alditol-d acetates. These hexose derivatives appear to be produced by the decomposition of D-glucose peroxy-radicals which are formed by the reaction of the primary radicals of D-glucose with oxygen. Bond scission of the peroxy-radicals yields triose, tetrose, and pentose. A radiolysis mechanism for the degradation of D-glucose in aerated, aqueous solution is proposed, based on the reaction of several kinds of D-glucose radical with oxygen.

Creepage discharge propagation in air and SF/sub 6/ gas influenced by surface charge on solid dielectrics

Influence of surface charging on creepage discharge propagation in air and SF/sub 6/ gas was investigated. The authors have employed a surface charging system using corona discharges, which permitted the deposition of surface charge on solid dielectrics with a given density distribution. By applying a lightning impulse across the charged surface of polyester film, they measured the discharge extension length as a function of surface potential generated by the surface charge. It was found that the impulse creepage discharges along the charged surface under a potential of 2 to 3 kV, extended a distance which was maximum 6/spl times/ longer than the case of the uncharged surface both in air and SF/sub 6/ gas. Experimental results were also discussed from the viewpoint of the specific capacitance, permitting their application to actual HV apparatus such as GIS. >

Development of a 6600 V/210 V kVA hybrid-type superconducting transformer

In this transformer, the low-voltage, high-current winding is made of liquid-helium-cooled superconducting wire and the high-voltage winding is made of liquid-nitrogen-cooled low-loss copper wire. The iron core is placed in a room-temperature environment outside the cryostat vessel. The cryostat vessel has a two-layer configuration of liquid-helium and liquid-nitrogen cooling vessels. The concept. design features, and measured characteristics of the H-SCT are described. Fundamental characteristics are obtained through short-circuit and no-load tests. The critical quenching current and in-rush current are also evaluated. >

A new furoxan derivative and its precursors formed by the reaction of sorbic acid with sodium nitrite

Abstract A new furoxan derivative ( 3 ) and its precursors ( 4a and 4b ) were isolated from the reaction mixture of sorbic acid with sodium nitrite, and their structures were determined by spectroscopic and X-ray crystallographic analysis.

Artificially triggered lightning experiments to an EHV transmission line

In a triggered-lightning experiment carried out on a mountain in Japan, thirteen strikes were obtained for the winter seasons of 1986 and 1987. The lightning occurred on the conductor and the tower of a 275 kV test transmission line, on the ground, etc. The authors outline the triggering method and the experimental results obtained from electrical and optical observations. Comparatively intense lightning with a current greater than 50 kA or a charge greater than 200 C was obtained. >

Transient distribution of metallic vapour concentration in a post-arc channel after current zero along the nozzle axis in a flat-type gas-blast quenching chamber

A method for estimating metallic vapour concentration in a post-arc channel on the basis of a spectroscopic method was proposed. Using the method, the axial distribution of metallic vapour concentration in a post-arc channel was measured around the nozzle throat in a flat-type gas-blast quenching chamber. In the chamber iron was intentionally used as an electrode material since Fe spectral lines at wavelengths of 426.0 and 442.7 nm have very much higher radiation intensities than particles such as , F or Cu at temperatures below 6000 K. The proposed method was capable of determining the iron vapour concentration up to after current zero in the experiment. It was found that has a magnitude around % along the nozzle axis during the period from -60 to after current zero for 5 kA arcs.

A novel approach to AC air arc interruption phenomena viewed from the electron density at current zero

Direct measurements were made of the time-dependent electron density around the current-zero period in a scaled-down air blast breaker with an interruption current level of a few kiloamperes, by means of the Thomson scattering of ruby laser light. The effects of interruption parameters such as the electrode material (copper and graphite) and the gas flow rate on the magnitude of the electron density in AC arcs were quantitatively investigated. The results showed that, in an arc current of 1.5 kA, the electron density at current zero in a copper electrode arc was significantly enhanced by a factor of 4-5 compared with that in a graphite electrode arc. Spectroscopy measurements have shown that such an increase in the electron density is brought about by the admixture of copper vapour with a concentration of 1.5% into high-temperature air at current zero. The electron density, however, was suppressed to around half the magnitude by the increase in the forced convection of air from 100 to 250 l min-1. The inter-correlation between arc interruption performances of the test circuit breaker and the electron density at current zero is discussed. Statistical analysis showed that the success rate of arc interruption of the circuit breaker decreases almost straightforward with increase in the current-zero electron density on the normal probability chart.

Response of a Wall-Stabilized Air Arc to Step and Sinusoidal Change in Current

Numerical calculations are performed with respect to transient characteristics of a 5-mm-diam wall-stabilized air arc at atmospheric pressure. The mass and energy equations are solved by means of a computer into which all the numerical data of the transport properties are memorized against gas temperature. The transient responses of temperature profile, arc conductance, and electric field strength to step and sinusoidal change in current are estimated. It is found that an arc time constant is given as a function of the axial temperature of arc column. The experimental results show good agreement with the calculated ones.

Transient behaviour of axial temperature distribution in post-arc channel after current zero around nozzle throat in flat-type SF6 gas-blast quenching chamber

The decaying behaviour of the axial temperature distribution in the post-arc channel after current zero is measured around the nozzle throat in a flat-type SF6 gas-blast quenching chamber. In the quenching chamber, iron is intentionally used as the electrode material. Two iron atom spectral lines at wavelengths 426 and 443 nm are detectable even up to 100 mu s after current zero for an arc with peak value of 5 kA. This is because the spectral lines for iron have higher radiation intensities than those for other species such as sulphur ions or copper atoms. From the radiation intensities measured at each of the five axial positions around the nozzle throat, the temperatures are estimated by means of the two-line method. The axial temperature distribution shows a local maximum at the nozzle throat up to a time of 20 mu s after current zero. However, the temperature at the nozzle throat decays more rapidly than at the other axial positions. At 100 mu s after current zero, the temperature at the nozzle throat reaches 3500 K, the lowest magnitude among the axial positions.