Dynamic Breakdown Characteristics Research Articles

Quench-induced Dynamic Breakdown Characteristics of HTS Pancake Coil Model for Resistive SFCL

Quench-induced dynamic breakdown (BD) characteristics of LN2 under transient bubble disturbance at the quench of HTS tapes are crucial to the reliable and rational insulation design of resistive superconducting fault current limiters (RSFCL). We have been investigating the dynamic BD characteristics using a nichrome pancake coil model for RSFCL using bifilar nichrome tapes as a heater. In this paper, we fabricated an HTS pancake coil model for RSFCL using GdBCO tapes and discussed the dynamic BD characteristics as a function of heat flux generated from the actually quenched HTS tapes.

Dynamic Breakdown Characteristics of Pancake Coil Model for Resistive-Type Superconducting Fault Current Limiters

Toward the reliable and rational insulation design of resistive-type superconducting fault current limiters (RSFCL), we have been investigating not only the intrinsic breakdown (BD) characteristics of liquid nitrogen (LN2) without bubbles but also the dynamic BD characteristics of LN2 under the transient bubble disturbance at the quench of RSFCL coils. We have so far used a fundamental model such as sphere-plane electrode system with quasi-uniform electric field. However, when RSFCL will be introduced in a future electric power network, a stack of pancake coils with non-uniform electric field will be adopted for the practical development of RSFCL. In this paper, we designed and fabricated a pancake coil model for RSFCL, and investigated the intrinsic and dynamic BD characteristics of the pancake coil models in LN2. Experimental results are discussed in terms of the volume effect of intrinsic and dynamic BD strength under non-uniform electric field.

Volume Effect of Dynamic Breakdown Strength in LN2 for Insulation Design of Resistive Superconducting Fault Current Limiters

Toward the practical and rational insulation design of a resistive superconducting fault current limiter, it is necessary to consider the electrical breakdown (BD) due to the transient bubble generation in liquid nitrogen (LN 2 ) at the quench of the HTS materials. We have been investigating the intrinsic BD characteristics of LN 2 without bubbles and the dynamic BD characteristics of LN 2 under transient bubble disturbance, respectively. In this paper, we have investigated the dynamic BD characteristics of LN 2 for different electrode diameters and gap lengths, and have discussed in terms of the volume effect of dynamic BD strength.

Breakdown Characteristics and Mechanisms of Liquid Nitrogen Under Transient Thermal Stress for Superconducting Fault Current Limiters

We have been investigating the electrical breakdown (BD) characteristics of liquid nitrogen (LN 2 ) with a transient thermal stresses to simulate the quench conditions of resistive-type superconducting fault current limiters (SFCL). We call such BD of LN 2 with the transient thermal stress as “dynamic BD,” and discriminate it from that with a continuous thermal stress. In this paper, we investigated the dynamic BD characteristics of LN 2 for different LN 2 pressures, electrode sizes, and terms of transient thermal stress input. In addition, we obtained the BD characteristics of LN 2 with the continuous thermal stress, and compared them with the dynamic BD characteristics. Furthermore, we analyzed the statistical scattering of the time from the thermal stress input to the dynamic BD occurrence and discussed the dynamic BD mechanisms of LN 2 . We also proposed a flowchart of rational and reliable electrical insulation design of resistive-type SFCL based on the dynamic BD characteristics of LN 2 .

Quench-Induced Dynamic Breakdown Characteristics of <inline-formula> <tex-math notation="TeX">$\hbox{LN}_{2}$</tex-math></inline-formula> and <inline-formula> <tex-math notation="TeX">$\hbox{LN}_{2}/\hbox{PPLP}$</tex-math></inline-formula> Composite Electrical Insulation System for Superconducting Power Apparatus

In HTS power apparatus, quench due to the fault current generates dynamic electrical/thermal combined stress. This stress may induce the electric breakdown (BD) under the operating voltage. We investigated the quench-induced dynamic BD characteristics of $\hbox{LN}_{2}$ . In addition we investigated the quench-induced dynamic partial discharge characteristics of $\hbox{LN}_{2}$ /polypropylene laminated paper composite electrical insulation system for HTS cables. The criteria of the combined electrical/thermal stress for the dynamic BD were obtained for both test samples, and the reduction rate of the dynamic BD criteria against the static BD criteria without thermal stress was discussed.

Static and dynamic breakdown characteristics of liquid helium for insulation design of superconducting power equipment

In this paper, we investigated quench-induced dynamic breakdown characteristics of liquid helium (LHe) under both non-uniform and uniform electric field. Experimental results for various quench conditions revealed that the dynamic breakdown voltage of LHe increased with decreasing the effective post-quench thermal energy density and with increasing the gap length and pressure, because of the suppression of thermal bubble disturbance in LHe. All of the experimental data enabled us to establish the 3-dimensionally systematized diagram of dynamic breakdown voltage of LHe as a function of effective post-quench thermal energy density, gap length and pressure.

Insulation performance of pressurized liquid helium under quench-induced thermal bubble disturbance for superconducting power apparatus

We have been studying quench-induced 'dynamic' breakdown characteristics of LHe and have already found that the electrical insulation performance of LHe was degraded drastically by the thermal bubble disturbance due to quench of superconductors. In this paper, in order to improve the insulation performance of LHe under quench conditions, we measured dynamic breakdown and prebreakdown characteristics of pressurized LHe. Experimental results revealed that breakdown voltage of LHe under quench conditions at 0.2 MPa was greatly improved, reaching 2 to 4/spl times/ compared with that at atmospheric pressure under both uniform and non-uniform electric fields. Moreover, for practical and efficient insulation design of superconducting power apparatus, we investigated the dynamic breakdown voltage of LHe as functions of pressure and gap length.

Dynamic breakdown characteristics of liquid helium induced by a quench of superconducting wire and coil

For practical insulation design of superconducting power apparatus, it is necessary to take into account an inherent phenomenon known as quench, the transition from the superconducting to the normal state. We investigated quench-induced dynamic breakdown and prebreakdown characteristics of liquid helium (LHe). Experimental results revealed that the quench of the superconductor drastically reduced the breakdown voltage of LHe in the thermal bubble disturbance. Moreover, dynamic breakdown characteristics in a quasi-uniform field using a superconducting coil were investigated. The results revealed that the breakdown was induced in the quench-initiated region where the largest thermal energy was generated.

High voltage insulation performance of cryogenic liquids for superconducting power apparatus

This paper describes high voltage insulation technology of cryogenic liquids for superconducting power apparatus. The insulation of a superconducting transformer is classified into several insulation components. Moreover, we investigate fundamental insulation characteristics peculiar to the superconducting and cryogenic circumstances: area and volume effects on breakdown strength, V-t characteristics, quench induced dynamic breakdown characteristics and so on. Finally, we systematize the electrical insulation of cryogenic liquids, and propose a flow chart for the practical insulation design of superconducting power apparatus.

超電導線のクエンチによって誘導される液体ヘリウムの動的絶縁破壊特性

超電導線のクエンチによって誘導される液体ヘリウムの動的絶縁破壊特性