Masaru Okamoto

Computer simulation of phenomena associated with hot gas in puffer-type gas circuit breaker

To analyze hot-gas flow in puffer-type gas circuit breakers (GCBs), a program was developed by adding functions for dealing with opening process, gas compression, and arcing to a program for the analysis of axially symmetric compressive fluids. The accuracy of the program is demonstrated by comparing the results of computation by this program with the results of two different tests: the observation of hot-gas backflows using the Schlieren method and the measurement of breakdown voltage drops resulting from hot gas generated by current interruptions. The results of both tests show trends similar to calculated results obtained by simulating the tests, proving that this program is applicable to interruption phenomena associated with hot gas to a certain extent. The program is applied to the calculation of pressure rise phenomena in a puffer chamber caused by hot-gas backflows and dielectric strength to ground in a tank-type GCB. The program is expected to be useful as a means of estimating test results. >

Current Limiting Function of Y-Ba-Cu-O Superconducting Ceramics

Meander-shaped superconductive ceramics, YBa2Cu3O7-x, with 30 cm in length were fabricated from green sheets by the doctor blade method. These ceramics were sintered and provided with electrode leads to make superconductive current limiting device (CLD).