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World's First 550 kV Single-Break Gas Circuit Breaker

The development and practical application of high performance arc-extinguishing chamber of gas circuit breaker is a key technology to realize compact and high capacity substations, and they made it possible to transfer large power to urban area.

World's First 550 kV Single-Break Gas Circuit Breaker

Toshiba developed a series of switchgears with higher voltage and current capacity during the postwar era of high economic growth. From around 1970, the company shifted its developmental efforts from air-insulated switchgear to gas circuit breaker (GCB) and gas-insulated switchgear (GIS) systems using sulfur hexafluoride (SF6), which has excellent insulation performance. GCBs with higher rated voltages, such as 300 kV or 550 kV, were initially realized by connecting multiple breaking points in series. However, further downsizing of GCB and GIS became an issue, so the factory and laboratory dealing with these systems worked together to reduce the number of breaking points.

In order to reconfigure a conventional 300 kV GCB with two breaking points into a single breaking point device, it was necessary to double the breaking performance. Moreover, a large-scale specialized test facility was required to perform the verification test of short-circuit performance. The world's largest short-circuit test facility was therefore constructed at Heavy Apparatus Engineering Laboratory, and by fully utilizing this facility, performance of a singlebreak 300 kV interrupting chamber was achieved through our original developmental efforts. We then applied this new technology to the world's first 300 kV single-break GCB, which was supplied to the Shin-Keiyo Substation of Tokyo Electric Power Company in 1982.

By replacing the double-break circuit breaker with the new single-break type, the height of GIS systems could be reduced and 300 kV underground substations became realized. This new technology was highly significant because it allowed large amounts of electric power to be efficiently supplied to urban areas where the installation of power sources is difficult. Initially, the rated breaking current was 50 kA, and it was increased to 63 kA. The hybrid puffer arc-extinguishing system is a key factor in this achievement. Hybrid puffer is Toshiba's original current breaking technology that utilizes the thermal energy of the arc during current interruption. 550 kV GCB with 2 breaks was developed, due to applying the technology of the 300 kV single-break GCB to 500 kV GCB with 4 breaks, In 1984, the first such system was delivered to the Buzen Substation of Kyushu Electric Power Company. This circuit breaker, which was utilized in a GIS, coupled with the technological innovations that had taken place in GIS systems such as the three-phase in common enclosure type main busbar, greatly contributed to the downsizing of the 550 kV GIS. A short-circuit current capacity of 63 kA and rated current of 8,000 A were also realized in response to the increase in system capacity.

In creating a 550 kV circuit breaker of the single-break type, further improvement of the breaking performance became necessary. Therefore, in addition to the hybrid puffer technology, we developed a dual-motion operation system. A conventional circuit breaker has a fixed contact and a movable contact, and only the movable contact is actuated. In contrast, the dual-motion configuration drives the movable contact in the usual way, while simultaneously driving another side contact in the opposite direction with one operating mechanism. This revolutionary technology greatly enhanced the relative operating speed of the contacts and played a major role in the realization of 550 kV single-break GCB. Toshiba's foresight in developing the dual-motion operation system is substantiated by the fact that other companies have been increasingly incorporating it into their systems in recent years.

We delivered the world's first 550 kV single-break GCB to the Shin-Tsukuba Substation of Tokyo Electric Power Company in 1993. 550 kV single-break GCBs were also incorporated into a GIS system, and has helped to achieve considerable reduction of required site area. In 1998, GIS of this type was supplied to the Shin-Toyosu Substation of Tokyo Electric Power Company, realizing the first 550 kV underground substation in the world. This substation has been attracting a great deal of attention, and even today many Japanese and overseas specialists make visits to study it.

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