Solid Insulated Switchgear Research Articles

Design of solid/gas composite insulation system with embedded electrode

Solid insulated switchgear (SIS) has been developed as a substitution for sulfur hexafluoride gas insulated switchgears in the medium voltage class. Its main circuit including a vacuum interrupter is coated with epoxy resin. An embedded electrode was employed in order to enhance the surface insulation performance for further miniaturization and higher stress design. In the previous studies, the surface insulation performance was examined by using a model electrode system which modified the electrode system of the moving part of SIS and the estimation method of the surface breakdown voltage was proposed. In addition, the simulation of the surface breakdown characteristics of a model electrode system was conducted and a design method was proposed. In the present study, the insulation performance of the solid part was taken into account and the insulation design was conducted using the proposed design method. The equivalent insulation distance was introduced and the partial discharge inception field strength was also taken into account. The insulation design was done for 22, 33 and 77 kV systems and the values of the design parameters were provided. In addition, it was found that two different types of the design concepts were available.

Development of high thermal conductive epoxy composite for large current switchgear

AbstractToshiba has developed solid insulated switchgear (SIS), which insulates the main circuit with epoxy composites. The solid insulating system is able not only to use no SF6, which is a kind of global warming gas, but also to supply compact equipment. In SIS, heat generated by the current loss in the conductors is dissipated through the epoxy composite. Therefore, development of high thermal conductive epoxy composites has been desired with respect to large current class SIS such as 2500 A. In this article, epoxy composite was filled with MgO having high thermal conductivity and SiO2 having low thermal expansion coefficient. The result of temperature rise analysis of 40.5 kV–2500 A SIS demonstrated that the high thermal conductive epoxy composite reduced rising temperature by approximately 10 K compared to conventional epoxy composite.

Basic study on surface insulation design of solid/gas composite insulation system with embedded electrode

Solid insulated switchgear (SIS) has been developed as a substitution for medium voltage SF6 gas insulated switchgear. Its main circuits including a vacuum interrupter are coated with epoxy resin and a solid/gas insulation system is formed. For further miniaturization and higher stress design, the authors investigated the surface insulation performance of the solid/gas insulation system containing an embedded electrode. In the previous study, the authors investigated the surface breakdown characteristics. The authors also investigated the surface discharge propagation characteristics and proposed an estimation method of the surface breakdown voltage. In the present study, the authors investigated the surface breakdown characteristics numerically. The calculation was done based on the estimation method proposed previously. The divided voltage ratio, the radius of the embedded electrode, the enhancement factor of the surface insulation strength and the peak value of the surface breakdown voltage are examined. As a result, the characteristics of the parameters and the criteria for the optimum insulation design were clarified.

大電流スイッチギヤを実現する高熱伝導エポキシ複合体の開発

Toshiba has developed solid insulated switchgear (SIS) which insulates the main circuit with epoxy composites. The solid insulating system is able not only to use no SF6, which is a kind of global warming gas, but also to supply compact equipment. In SIS, heat generated by the current loss in the conductors is dissipated through the epoxy composite. Therefore, development of high thermal conductive epoxy composites has been desired with respect to large current class SIS such as 2500 A. In this paper, epoxy composite was filled with MgO having high thermal conductivity and SiO2 having low thermal expansion coefficient. The result of temperature rise analysis of 40.5 kV - 2500 A SIS demonstrated that the high thermal conductive epoxy composite reduced rising temperature by approximately 10 K compared to conventional epoxy composite.

Estimation of surface breakdown voltage of solid/gas composite insulation with embedded electrode

Solid insulated switchgear (SIS) has been developed as a substitution for medium voltage SF6 gas insulated switchgear. Its main circuits including a vacuum interrupter are coated with epoxy resin, therefore, a solid/gas insulation system is formed. For further miniaturization and higher stress design of SIS, the authors investigated on the surface insulation of the solid/gas insulation system containing an embedded electrode. In the present study, the surface breakdown voltage was estimated based on the surface discharge propagation characteristics. From the measurement of the surface flashover voltage on a dielectric against the surface distance, the relation between the surface flashover voltage and the surface distance was found to be expressed with an equation derived from the empirical equation presented by Toepler. Then, the surface breakdown voltage was estimated based on the obtained equation. The estimated values were compared with the experimental data obtained varying a parameter of the radius of the embedded electrode, thickness of the epoxy resin plate or the radius of the plate. As a result, a good correlation was obtained. Therefore, the estimation method of the surface breakdown voltage on the solid/gas insulation with embedded electrode was established.

Improvement of insulation performance of solid/gas composite insulation with embedded electrode

Solid insulated switchgear (SIS) has been developed as a substitution for medium voltage sulfur hexafluoride (SF 6 ) gas insulated switchgears. Its main circuit including a vacuum interrupter is coated with epoxy resin. Therefore, a solid/gas insulation system is composed. For further miniaturization and higher stress design of SIS, improvement of the insulation performance is required. In the solid/gas insulation system, the breakdown strength along the surface is lower than that of solid. Then, the authors investigated the surface insulation performance of the solid/gas insulation system containing an embedded electrode. In the present study, the sizes of the embedded electrode and the solid insulation material were varied and the partial discharge inception voltage and the surface breakdown voltage were measured. As a result, it was found that the surface breakdown voltage varied considerably with the radius of the embedded electrode. From the result, it was deduced that the surface insulation performance could be improved by choosing the size of the embedded electrode appropriately. Moreover, the effects of the thickness of the insulation material and of the surface distance on the surface insulation performance were clarified.

Solid insulated switchgear and investigation of its mechanical and electrical reliability

AbstractSF6 gas is widely employed in medium‐voltage switchgear because of its high insulation reliability and down‐sizing ability. However, SF6 gas was placed on the list of greenhouse gases under the Kyoto Protocol in 1997. Since then, research on low‐SF6 or SF6‐free insulation has been carried out actively. Therefore, we focused on solid materials with higher dielectric strength than SF6, and we have now developed solid insulated switchgear (SIS) that uses molding of all main circuits. A new epoxy casting material is used which contains a large amount of spherical silica and a small amount of rubber particles. This new material has high mechanical strength, high thermal resistance, high toughness, and also high dielectric strength because of direct molding of the vacuum bottle, as well as reduced size and high reliability. This paper describes the technology of the new epoxy casting material which makes possible SIS. In addition, mechanical and electrical reliability tests of SIS using a new epoxy resin were performed, and the effectiveness of the developed material and the mechanical and electrical reliability of the SIS were verified. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(4): 28–36, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21057

Mechanical Reliability(Life-Time) Estimation for 25.8kV Eco Solid Insulated Switchgear

In this paper, mechanical reliability(Life-time) estimation method for 25.8kV SIS(Solid Insulated Switchgear) has been studied. Recently enacted KEPCO's standard includes clause that have to submit a warrantable reliability data for life-time(over B10 25 years) of an epoxy-solid insulating material. Accordingly, this research was carried out on the ALT(Accelerated Life Test) and Life-Estimation method for SIS's insulating material. Mechanical life-time estimation for SIS's insulating material is to verify reliability for tensile creep & fatigue stress, which is the major mechanical stress of SIS. This study proved that SIS's reliability for mechanical stress and established that confidence for estimation results in further verification test.

Solid Insulated Switchgear and Investigation of its Mechanical and Electrical Reliability

SF6 gas is widely employed in medium-voltage switchgear because of its high insulation reliability and down-sizing ability. However, SF6 gas was placed on the list of greenhouse gases under the Kyoto Protocol in 1997. Since then, research on low-SF6 or SF6-free insulation has been carried out actively. Therefore, we focused on solid materials with higher dielectric strength than SF6, and we have now developed solid insulated switchgear (SIS) that uses molding of all main circuits. A new epoxy casting material is used which contains a large amount of spherical silica and a small amount of rubber particles. This new material has high mechanical strength, high thermal resistance, high toughness, and also high dielectric strength because of direct molding of the vacuum bottle, as well as reduced size and high reliability. This paper describes the technology of the new epoxy casting material which makes possible SIS. In addition, mechanical and electrical reliability tests of SIS using a new epoxy resin were performed, and the effectiveness of the developed material and the mechanical and electrical reliability of the SIS were verified. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(4): 28–36, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21057