Research on Discharge Characteristics in Ultra-high Pressure Gases (Supercritical Fluids): A Brief Review

This paper provides a review of the research on discharge characteristics in ultra high pressure gases (supercritical fluids) and discusses different applications in various fields. Followed by a summary on the investigations performed on the application of supercritical fluids for power switching purposes. A brief overview of the open research questions related to characterization of ultra high pressure switching arcs concludes the paper

Impact of Ablation Based Self Blast Nozzles on Load Break Switch Current Interruption Performance

In this contribution, SF6 free ablation assisted medium voltage load break switchgear, has been investigated. In these switches, gases generated by the arc polymer interactions are trapped in expansion chambers and are released back onto the arc at the current zero crossing. This increases the current interruption capability of the switch without the use of additional mechanical parts, as opposed to using a puffer to blow on the arc. Existing self-blast research, in medium voltage load break switchgear, has focused on blowing axially or tangentially onto the arc in a cylindrical arcing channel. More geometries are possible. In this paper, alternative self-blast blow-position and the presence of obstructions in the arcing channel have been investigated experimentally and with cold flow simulation. It has been determined that blowing right onto the arc centre is not optimal for cooling the arc, and that the presence of an obstruction in the arc channel is beneficial to arc interruptions

Characterization of Ultrahigh Pressure Nitrogen Arc Using Black Box Arc Model

In this paper, the effect of filling pressure on the black box arc parameters of nitrogen arc is reported using Mayr arc model. The arc current is approximately 130 A at 190 Hz. The filling pressure is varied at absolute pressure of 1, 20, and 40 bar. A phase transition from gas to supercritical state occurs when the pressure of nitrogen exceeds 33.5 bar at room temperature. To determine the effect of forced cooling, first, the free-burning arc is studied at different filling pressures. Afterwards, a self-blast arrangement is used where gas is blown into the arc near current zero. It has been observed that, without forced gas flow, both the time constant and the cooling power of the arc increase with the filling pressure. The forced cooling, however, reduces the time constant and further enhances the cooling power, thus facilitating the current interruption

Dynamic characteristics of optical intersecting-waveguide modulators/switches with curved electrodes

金沢大学工学部The dynamic behavior of optical modulators/switches in the form of intersecting waveguides with curved electrodes is formulated. It is shown that the electrode curvature is very effective in achieving reflected pulses in good resemblance to the incident ones. Further, the speed of operation is found to be high and is shown to depend, besides the commonly known capacitance of the device and the time required for refractive index variations to settle down, on the relative pulsewidths of the optical and modulating signals and the extent of their synchronization. The intersection angle is found to influence the propagation delays of the spatial components, which are equalized by properly chosen structural parameters, to achieve unbroadened and undistorted output pulses. The flexibility in the bandwidth of even a fabricated device, through adjustment of the driving conditions, is demonstrated and the capability of such devices to handle a very wide range of optical pulsewidths is clarified

Comparative study on various dielectric barriers and their effect on breakdown voltage

Non-pressurised air is extensively used as basic insulation medium in high-voltage equipment. Unfortunately, an inherent property of air-insulated design is that the system tends to become physically large. On the other hand, the application of dielectric barriers can increase the breakdown voltage and therefore decrease the size of the equipment. In this study, the impact of dielectric barriers on breakdown voltage enhancement is investigated under both direct current (dc) and alternating current (ac) applied voltages. For this purpose, three kinds of dielectric barriers in two different high-voltage electrode structures are investigated. In the first structure, several experiments are carried out with four different electrode arrangements, keeping the inter-electrode gap constant while varying the position of the dielectric barrier between the electrodes. In the second structure, the inter-electrode gap is varied while the high-voltage electrode is covered with dielectric materials. The influences of different parameters such as inter-electrode spacing, electric field non-uniformity factor, and dielectric materials on the breakdown voltage are investigated for applied 50 Hz ac and dc voltages. In addition, a simulation model to approximately calculate the breakdown voltage is proposed and validated with the experimental results

Comparative study on various dielectric barriers and their effect on breakdown voltage

Non-pressurised air is extensively used as basic insulation medium in high-voltage equipment. Unfortunately, an inherent property of air-insulated design is that the system tends to become physically large. On the other hand, the application of dielectric barriers can increase the breakdown voltage and therefore decrease the size of the equipment. In this study, the impact of dielectric barriers on breakdown voltage enhancement is investigated under both direct current (dc) and alternating current (ac) applied voltages. For this purpose, three kinds of dielectric barriers in two different high-voltage electrode structures are investigated. In the first structure, several experiments are carried out with four different electrode arrangements, keeping the inter-electrode gap constant while varying the position of the dielectric barrier between the electrodes. In the second structure, the inter-electrode gap is varied while the high-voltage electrode is covered with dielectric materials. The influences of different parameters such as inter-electrode spacing, electric field non-uniformity factor, and dielectric materials on the breakdown voltage are investigated for applied 50 Hz ac and dc voltages. In addition, a simulation model to approximately calculate the breakdown voltage is proposed and validated with the experimental results

Partial Discharge Inception in Ceramic Substrates Embedded in Silicone Liquid, Silicone Gel, and Mineral Oil at Fast Voltage Rise and Sinusoidal Voltage

This paper summarizes experiments that were carried out on insulating ceramic substrates and a needle-plane arrangement with the purpose to characterize the inception of partial discharges (PD) in the insulation of high-voltage semiconductors. PD measurement results obtained on substrates are correlated with the high-field pre-inception currents measured in a needle-plane electrode arrangement in liquids and gel. The tested substrates were embedded in either silicone liquid, silicone gel, or mineral oil. The PD inception was measured at sinusoidal and switched voltage of different polarities and rise times. For all test objects, the PD inception voltage (PDIV) is significantly lower under switched voltage compared to the sinusoidal voltage. Silicone gel and silicone liquid as insulating media surrounding the substrate are similar in terms of the PDIV. The PDIV is lower for substrates placed in mineral oil, particularly under switched voltage. Silicone gel and liquid are characterized by very low pre-inception currents measured at a high electric field. In contrast, a higher pre-inception current is observed in mineral oil. These results are consistent with the hypothesis that the high pre-discharge current in the more conductive mineral oil leads to space charge build-up in the high-field region that, by deforming the electric field, affects the PD inception probability.acceptedVersio