Hitoshi Mizoguchi

Development of novel hybrid puffer interrupting chamber for SF/sub 6/ gas circuit breaker utilizing self-pressure-rise phenomena by arc

A novel puffer interrupting chamber is developed which is designed to evaluate pressure rise by guiding the thermal energy of the arc effectively into a puffer cylinder. This interrupting chamber has high blasting pressure, suitable for interrupting from low up to high current levels, providing interrupting performance considerably better than that of conventional interrupting puffer chambers. Particularly, its performance during short arcing is excellent, providing reduced minimum arcing time. For an 84 kV, 31.5 kA interrupting chamber, pressure calculations on an arc model and interruption tests were conducted to compare the interrupting performance of the new chamber with that of a conventional double-flow puffer interrupting chamber. >

Study of Thermal Runaway/Equivalent Prorated Model of A ZnO Surge Arrester

Zinc-oxide surge arresters experience thermal runaway when the temperature rises beyond the permissible limit. This phenomenon is created by increased leakage current resulting from a resistance drop of ZnO elements in the low current region which occurs along with the temperature rise.

Development of an interrupting chamber for 1000 kV high-speed grounding switches

High-speed grounding switches (HSGS) for 1000 kV (UHV) transmission lines are required to interrupt a delayed zero current with a long arcing time. This requirement was met by allowing pressure rise in the opening operation to last efficiently for a long time through optimizing the exhaust volume and the residual volume of a puffer-type interrupting chamber and utilizing the effect of pressure rises due to arcing.

Investigation of Technology for Developing Large Capacity and Compact Size GCB

New effective technologies to increase the interruption capacity and to the reduce size of a gas-insulated circuit breaker (GCB) are shown. One is the adoption of a new nozzle shape that improves the cooling of the arc. The other is the investigation of hot gas diffusion in the exhaust cylinder related to the dielectric strength recovery after the current interruption. It is shown that these technologies are useful for increasing the interrupting current from 50 kA to 63 kA.

Investigation of interruption performance of newly developed 300 kV 3-phase-in-one-tank-type GCB and its application to a reduced size GIS

With the objective of diminishing the distance between bays of SF/sub 6/ gas insulated switchgear (GIS), a 300 kV three-phase-in-one-tank-type gas circuit breaker (GCB) has been developed. The size of the interrupting chamber has been reduced to decrease the diameter of the GCB tank. Hot gas flow has been optimized analytically and the deterioration of insulation performance caused by the hot gas between the poles has been investigated. A more compact GIS with fewer parts and easier to install results from the study. >

Factors Influencing the Interrupting Ability of SF 6 Puffer Breaker and Development of 300kV-50kA One-Break Circuit Breaker

The factors to be considered at the design stage of the extinction chamber of a SF6 puffer gas circuit breaker (GCB) have been examined numerically and analytically. It has been shown that an extinction chamber which satisfies both Short Line Fault (SLF) and Breaker Terminal Fault (BTF) conditions simultaneously is not economical and a capacitor parallel to it should be used. On the basis of the above analysis, a 300kV-5OkA one-break chamber has been developed successfully.

Investigation of two types of interrupting chamber with low drive energy and development of 245-kV GCB

In an attempt to generate high pressure with small driving energy, two types of interrupting chamber, two volumes-two pistons-type, and one volume-one piston-type are compared by simulating opening operating characteristics. As the result of the simulations, we concluded that one volume-one piston-type chamber could generate sufficient high pressure and ability to interrupt high current with a simpler structure and limited operating energy. A new GCB for 245-kV GIS adopting the new chamber has been developed.

Development of Loop Current Interrupting Disconnecting Switch for Gas Insulated Switchgear

A magnetic driving type disconnecting switch has been developed which is capable of interrupting loop current in gas insulated switchgear (GIS). The disconnecting switch (DS) consists of a coil installed in the vicinity of electrode which produces a magnetic field of about 0.02 T/kA during interruption. The magnetic field rotates arcs, resulting in the enhancement of interruption. Thus, less dust is produced due to the melting of electrode materials, and consequently a withstand voltage after many loop current interruptions was improved compared with that of a conventional free burning type disconnecting switch.

A study on a compact three-phase encapsulated GCB

To develop a compact three-phase encapsulated gas circuit breaker (GCB), particular consideration must be given to the mechanical and electrical effects of electromagnetic force and hot gas between poles, which are characteristic of the three-phase encapsulated structure, in addition to efforts to make a compact interrupting chamber and minimize driving energy. Employing an interrupting chamber with a novel concept, and after investigating and proof-testing important items, a 145 kV /40 kA GCB was developed for gas insulated switchgear application.<<ETX>>

Development of an interrupting chamber for 1000-kV high-speed grounding switches

In Japan, construction of 1000 kV (UHV) transmission lines is planned in order to deal with the expected increase of electric power demand. On the line, after the fault current is interrupted by circuit breakers, the arc caused by electrostatic induction current remains for a long time because of its high voltage. To re-energize the fault line after arc extinction, a new circuit breaker reclosing system which has high-speed grounding switches (HSGS) installed at both ends of the line is employed. If, while the HSGS is interrupting an electromagnetic induction current, a ground fault takes place in another energized line, causing a shirt-circuit current including a dc component to flow, the large dc component is superimposed on the HSGS current, producing a zero shifting state with no passage through the zero point for long time. Such zero shifting durations are estimated to be up to about 80 ms. Therefore HSGS are required to interrupt this delayed zero current as a special duty. This requirement is met by a newly developed puffer interrupting chamber allowing a long pressure rise by optimizing the exhaust and residual volume of the puffer cylinder and utilizing the effect of pressure rise due to the arc.